Doctor's Note

Sweet potatoes are cheap, healthy, nutrient powerhouses—check out my last video: Anti-Cancer Potential of Sweet Potato Proteins.

What about cooking methods for other vegetables? See my video Best Cooking Method.

Want more information about acrylamide, the potential crispy carb carcinogen? See my video Cancer Risk from French Fries. And for why deep frying in general might not be good, Deep Frying Toxins and Carcinogens in the Smell of Frying Bacon.

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  • drdeb

    Thank you Dr.Greger for another excellent video. I am looking forward to your book, congratulations! I will be eating my organic sweet potatoes with the skin on by boiling them rather than my usual baking

    • george jacobs

      What about the water after boiling?

      • Wegan


      • Lawrence

        You can simmer the Sweet Potatoes along with other veges to make a stew. Start with beans because they take the longest to cook. Then add garlic and onion and any spices you wish to use (eg Turmeric & black Pepper). Depending on how much water these is after simmering until soft, you can then choose to thicken it with Arrowroot or not. Its a one pot meal which is easy to make.

        • Steve Weltman

          Yum! I am eager to try this. Sweet potatoes are so good, it’s tough to believe that they are this good for the human body.

      • linda

        After boiling sweet potatoes, I normally poured its water out into a glass then drink it.

    • srut

      Dr Gregor, What do you about using a pressure cooker. Can you cut up the potatoes to make them cook quicker?

      • Señorita

        pressure cookers are wonderful for cooking potatoes. yes, clean them, cut them up – it’s incredible and so fast. a suggestion for a book is Jill Nussinow’s ” the New Fast Food” and there is an InstaPot support group on Facebook.

      • Ineke

        well as a profesional I was explained to, with the help of a video, never never use a microwave for it will kill the good fibes in veggies.
        A pressurecooker seems to be the best to cook your meals.
        I realy love this even as we do live at France, thank you very much!

        • Jack Zelver

          There’s a lot of misunderstanding and urban lore about microwaves and their dangers. Microwave ovens operate at the frequency of water molecule resonance. So the water in foods absorbs the microwave energy and heats up. The waves pass through dry non-metals and have no effect, and they’re simply reflected by metals.

          Foods in microwave ovens cook a little like an “internal boiling” process: the water in the food heats and cooks the rest of the food. That’s why Dr. Greger mentions that microwaved sweet potato skins are harmed far less than baked ones.

          I assume your “professional” is a chef, and sad to say, just like the rest of us, they sometimes have ideas that are pure fiction and not scientific fact.

          I don’t know how you’d show it would “kill the good fibes in veggies”, nor do I really know what that even means!

          • Ineke

            thank you Jack for your reply and certainly will look into this matter, more.

            By ‘Professional’, I am that, in this case for I have been tought as a orthomoleculair health practitioner to advice patients not to use a microwave…

          • Jack Zelver

            Ineke, if you’d like a little more info, I’d suggest the Wikipedia page called “Microwave oven”. In particular, the part on the effect on foods:

          • Doctor Greybeard

            A health professional’s credibility is enhanced by proper spelling, and by correct use of terminology. I suggest you use “advise” (it’s the verb you wanted) instead of “advice” (it’s a noun). I suggest you use ‘orthomolecular”, and ‘taught’ in place of the words you used. I also suggest, as Mr Zelver hinted at, that you research this topic from peer reviewed science sources. Your posts make it clear that you need to learn more about this topic.

          • Wegan

            Ineke lives in France per the first post. Things can get lost in translation.

          • shervan

            There have been several studies done concerning microwaves, and the destruction of nutrients… no I will never use my microwave, why should I when I have a stove, pots n pans and an oven.. Im not lazy, I like to prepare my meals without nuking them

          • RalphRhineau

            Could you please provide links to said studies?

            Remember, the meat, dairy, egg, and fisheries industries all are busy churning our “studies” and we know what a bunch a hooey most of those “studies” are… all too often, they’re deceptions fabricated by scientists who are willing to whore themselves to advance their employers’ position. People who are into more healthful eating are not above using the same tactics.

            I’m *not* saying the authorities you’re alluding to are among those deceitful people, but until I see the the studies you’re alluding to, I’m disinclined to but much stock in what you’re asserting.

          • The sources are underneath the video in the tab sources cited. You may have to jump around a little as many of those are short article clips but most of them seem to link to the full one.

          • RalphRhineau

            Sarah, since Shervan was the one making the claim that microwaving destroys nutrients, it would’ve been thoughtful to let us know what studies he/she was alluding to instead of expecting others to go search for their supporting studies. When I did do a search for ‘microwave’ in the titles of the cited studies, there were *no* occurrences of the word. When I opened the links that referred to the thermal processing of the sweet potatoes, again no occurrences of the word ‘microwave’ though one alluded to four unspecified “heating processes”. I did see several statements comparing boiling/wet and baking/dry comparisons. Unless you or she/he share the references, my inclination is to conclude he/she offered unsupported opinions as fact and tried to gussy them up with the FoxNews trick of “some people say…”.

            Shervan’s course welcome to cook as she/he likes, but availing oneself of an effective tool like a microwave oven to save time is like choosing to availing oneself of a pressure cooker (or is that use of *unnatural* high pressure a problem there, too?)

            His/her pejorative use of the word “nuking” is objectively incorrect as microwaves are so low in energy that they could no more affect the nuclei of atoms than squirt gun could moisten the interior of a walnut. Microwaves heat food by causing molecules to vibrate and wiggle so much and so fast that heat is poduced by friction in the same way your hands heat up when you rub your plams briskly together.

            Fundamentally, it’s the elevated temperature that damages the nutrients, irrespective of whether its applied via a lot of boiling water, a hot oven, a frying pan or a microwave. The reason boiling is often worse than microwaving is because the water leeches out the nutrients. In microwaving, the nutrients have nowhere to go and thus are retained.

            In fact, it’s the ability of microwave ovens to heat food so quickly that results in a *minimization* of the loss of nutrients as you might want to see at Doc G’s video on best cooking methods: ( Interestingly, with green beans microwaving *increases* the antioxidant power in contrast to boiling/pressure cooking which degrade antioxidant power.

            In closing, I find myself wondering why Shervan even owns a microwave oven given her/his antipathy/fear of it. Afterall, who knows what other dangerous effects a device this powerful could have on other foodstuffs or even the molecular structure of water itself?

  • BB

    I cook Sweet Potatoes with brown rice favored with tamari, garlic, ginger and onions. I always put them in my black bean chili. The sweet of the potato balances the spicy chili.

    • Penny

      Pumpkin is another great thing to put in chili. You can’t taste it, but it has a great texture for chili and helps balance out the spiciness as well :)

    • Carol J

      That sounds delicious!

    • srut

      Sounds good. how much water do you use if you use a cup of brown rice. This is my first time replying to these posts and I mentioned a pressure cooker. How will Dr Gregor see my posted and will I be sent an email? Thank you. So many great ideas

      • Thea

        srut: Dr. Greger used to reply to posts as often as he could. But this site and number of posts grew to the point where Dr. Greger could no longer participate personally. However, there are some great people who participate in these discussions. Hopefully they will reply to your post.

        For myself, I will say that I LOVE my pressure cooker. But I don’t have a lot of experience cooking potatoes in it. So, I can’t offer specific advice. The bit of help I can shed is to recommend my favorite pressure cooker book:
        Great Vegetarian Cooking Under Pressure. (It says vegetarian, but is really almost all vegan.) This book is well organized and has great recipes. I’m pretty sure the book would have information about cooking potatoes in it.

        Good luck.

      • thorn324

        I have two pressure cookers, and both came with a basic but nonetheless helpful owner’s/user’s manual that include times for such things as grains (white and brown among others), root vegetables (such as potatoes), other vegetables (fresh and frozen), dried beans/legumes. Who could ask for anything more?

        Well, some of us could! And I recommend not only the cookbook Thea mentioned (in an earlier post) but also another by the same author Lorna Sass: her *Complete Vegetarian Kitchen* is–like *GVCuP*–really a vegan cookbook. *CVK* is somewhat more basic in that it includes general information about a wide number of non-animal foods, instructions for cooking essential ingredients as well as dishes using those ingredients (e.g., plain rice as well as rice pilaf), and directions for cooking everything in the book using either a pressure cooker or regular (meaning non-pressurized) methods. I have and use both guides often.

  • Veganrunner

    Man are we getting smart!

  • Leslie

    What do you make of this study claiming that EPA, when taken in greater quantity/amounts/ratio than the DHA, is what has the most benefit on depression?

    My concern is that vegan algal oil has more DHA than EPA, and if someone was taking this for depression it might not work out so great. I know of some who actually get depressed after taking DHA in excess of EPA, and noticeably. Thank you for any thoughts on this study, and VEGAN ways to get more EPA in the diet than DHA. It seems difficult to maximize EPA, while intaking some (but less) DHA, as vegan DHA pills favor more of the DHA, but maybe there is a way with other vegan foods.

  • Leslie

    Are the Japanese purple potatoes from the nightshade family? I’ve seen them advertised as “purple sweet potatoes”, but have also been told they are a nightshade, and sweet potatoes are not a nightshade.

    • LynnCS

      Good question. I need to know that. Dr. Greger?

    • Brigitte

      Hi Leslie! Maybe a confusion with the purple potato, which is a potato though it’s purple?

  • Tobias Brown

    Do you boil it whole? Does boiling in small pieces cause nutrient leeching?

    • Gross Bro

      I cut my sweet potato into cubes… the water stays clear after cooking, which can’t be said about other vegetables.

  • Sandy

    I’d think that steaming sweet potatoes would be a lot better and quicker and the vitamins would remain intact.

    • Carol J

      In the video Dr. Gregor said that the water when boiling acts on the sweet potato in a way that likely makes its micronutrients more bioavailable to us. Sometimes plants have more vitamins/nutrients when raw or steamed but our bodies can’t absorb them — one of the reasons studying nutrition is so darn interesting. But as Dr. G said, the sweet spuds are packed with nutrition, so prepare them however you like.

  • Bruce

    Are there any health risks associated with eating sweet potatoes raw?

    • Brenda

      If you freeze the video where he is showing the graph, raw appears even better than boiling. Steaming (mentioned in comments by someone else) is barely better than baking. Raw wins – though I don’t think I could consume all that much raw – what do you do with them raw?

      • AnnMarie

        I make dehydrated sweet potato chips with them. The slices need to soak for a good long while in order to draw out starch – the consistency doesn’t work otherwise. I’veThanks for calling my attention to the chart. Roasting is different than baking, though, in that roasting is usually done with chopped potatoes and baking typically refers to the whole potato with some fork punctures in it. The temperature would be about the same but the amount of flesh directly exposed to the heat would be different. I wonder if the skin would have a nutrient protective effect…

        • Brenda

          I own a very nice dehydrator. when I bake I cut up into disks so maybe I am really roasting under the broiler – never said I was a chef :). If raw is best then not sure it is worth the effort once I slice with the mandolin to dehydrate – just eat them raw.

        • LynnCS

          Not sure what is meant by soaking to draw out the starch. Don’t we want the starch? I’ve been making chips in the microwave with no prep. Would love to hear more. Thanks. Lynn

          • The soaking is culinary rather than nutritional. I found that just thinly slicing (with a mandoline) the potatoes would result in a chewy chip. Soaking, them, however, draws out some of the starch so that they become crisp as they dry. This is only for preparing them raw. I’ve also done that to make raw potato sweet potato salad & raw sweet potato purée. The resulting texture is smoother with the soaking.

      • Alex

        I see a smoothie opportunity here!

        • Ben

          I do them in smoothies, both raw and boiled. The boiled ones taste better in smoothies, especially the dark orange ones, they are creamier when boiled. I haven’t tried the purple ones in smoothies yet, though. I have to go to a Asian market to find those. The skin of the purple sweet potatoes does not taste so good, but in a smoothie maybe it wont be noticed.

          • Shannon

            I only eat them raw – with skins – in smoothies with potent, organic frozen blue, black and strawberries, and don’t forget the kale or spinach! I healed my colon cancer that way in just 2 months – three times a day. They are definitely a superfood! It really does take a Vitamix to liquefy them in my experience. Brown smoothies, yes, but OH! So delicious!

          • Charmaine

            Dear Shannon, that’s wonderful news and very interesting. Thanks for posting your comment.

          • Shannon

            Thank YOU for the sweet reply! I just figure, nature intended raw fruits and more studies than not say that nutrients are lost in heating. We have hands for picking, but no stoves or microwaves in nature. I just know it worked for 4th stage colon cancer as I mentioned, in about 60 days, perfect blood, no anemia, perfect 3X per day elimination, no more tarry stools and felt amazing. (I’ve been vegan for 10 years, never felt better, but moved to a small town that didn’t even have a health food store or any organic produce. After 6 months eating unclean (non organic) food, including meat, my body went into shock and I had Rheumatoid arthritis, thryoiditis, eczema, then colon cancer! I then read if you eat clean for a very long time, then “dirty”, your body cannot handle the toxins; cannot use or digest that food and cancer and autoimmune disease often follows. As a former nurse ALWAYS studying food, It killed me (almost literally) to have to eat the swill here in the midwest. Thankfully, a Natural Grocers opened up and I went right to it, just in time. I know many people that have reversed cancer, diabetes, heart disease, autoimmune syndromes by eating this way. I am not fully raw, but I rarely cooked when I was treating the cancer. I just hope this helps someone out there. It’s amazing how food can heal and so fast!! Have a great day, Charmaine!

          • Thea

            Wow Shannon. That’s such a powerful story. I second Charmain in thanking you for your post.

          • Shannon

            You’re entirely welcome, and thank you for being such a great source of information on this forum!

          • Maria

            That is amazing Shannon! What else did you do to reverse your cancer?

          • maria

            That is amazing Shannon! May I ask what else you did as an anti-cancer protocol to reverse your cancer?

          • Shannon

            Hi, Maria,
            I just ate superfoods – LOTS of garnet yams, blue, black, strawberries & raspberries, ZERO sugar or any simple sugars, but healthy carbs like quinoa, steel cut oats & spelt, (in moderation), bunches of spinach and kale (3Xper day, the smoothies), 2 avos a day. Of course strictly vegan, supplemented with organic virgin coconut oil 2 tbsp. per day, and TONS of organic pinto beans, homemade hummus, immense amounts of onions & garlic, enjoying cloves and plain raw onions for munchies, lol. Took Bio Cicumin (Life Extension) daily, meditated and used visualization techniques – KNOWNG it was leaving my body. Some passive light Pilates, stretching when I felt good, even if only a minute. Lots of distilled water, (unsweetened Silk almond milk in smoothies because it’s non GMO and no kind of hidden sweeteners in it). Walnuts, raw pumpkin seeds and many hours of sleep. You have to attack it from all angles, physical, mental, spiritual and emotional. Have a new goal or get back to what you love to look forward to. Talk to your cells and body!! Mostly, don’t just believe, but hold the feeling of already being vibrantly healthy during quiet time. And your support network is so important! Make sure you tell them you love and appreciate them! Continue doing for others, even just online if you’re not up to going out. Obviously, the cut, burn, poison was never even a consideration for me. I am not a doctor, and this is just my journey, but it worked for me and I’ve seen it work for other people I know. I’ve read many others stories much the same. It is a lot of work if you want to call it that, taking care of yourself, but it’s important when the stress and bad “food” has resulted in disease. You can’t go back to the old ways or it will return more than likely! This has to be a lifestyle and it will more than pay off.
            Keep love and compassion in your heart always because anger, hate, envy, jealousy, worrying, etc. are the root cause of dis-ease as is chemically laden and foods that are not right for the human body. It just manifests in the body before people notice how bad they feel sometimes. Start your day out with gratitude for everything that you have and all the loved ones in your life and be in the moment. Many people live their lives in the future, forgetting what’s right here and now and miss it.
            I hope this helps you in some way, too. :-) Spread the word and love!!!

          • Eric

            Congratulations for healing, Shannon. “We have hands for picking, but no stoves or microwaves in nature.” I am just curious but blenders like Vitamix also don’t occur in nature so how come we can make an exception of blenders but not of stoves or microwaves, even though blending obviously does better than our teeth do at extracting nutrients from food?

          • Peter R. Mare

            We purchased a Soya Power G4 that makes great hot and cold milks from grains, nuts & seeds

        • Brenda

          Oh well, i don’t do smoothies, juicing.

      • fineartmarcella

        I just cut them up in thick slices and eat as part of lunch or a snack, the Garnet variety are as sweet as candy almost, they have a darker orange/red insides, I get them at WF and they are yummy! Thanks for pointing out the graph, that was my question was on how good for us they are raw compared to cooked

        • Brenda

          I do not have access to a Whole Foods, yet. We are getting one spring of 2016 – yeah! No idea what variety mine are – they are shipped in from NC. I’m hoping my CSA has them or I may start growing them myself.

      • GoGamecocks

        Sweet potato slaw!

      • Ben

        But keep listening to the video, the boiling increases bio-availability of nutrients with a gelatinizing effect. So boiling might actually win. Your bio-availability is too low on raw.

        • Brenda

          I’m fairly new to the whole thing. bio-availability as in ability to use the nutrients? So they are somehow locked up in raw form? I caught boiling lowering glycemic but if that wasn’t an issue, boiling still trumps raw?

      • MikeMuse

        I Juice them and buy them perfectly smaller than the chute for the juicer. Skin and all is best and this way you can use the pulp if you choose.

        • Brenda

          Dr. Esselstyn told me no juices of any kind. My triglycerides were 600 so I stick with whole foods.

    • Because they are mildly goitrogenic, some practitioners advise folks who have thyroid disease not to eat them raw. That’s the only caution I’ve ever come across.

      • Shannon

        I have battled thyroiditis for 20 years and they had zero effect on my problem. As a former nurse, I also take Armour thyroid; Synthroid looks good on TSH (worthless test), but often doesn’t actually affect the total T3-T4 conversion process, resulting in “normal” labs, but symptoms and illness remain.

        • Peter R. Mare

          My wife, Terry has had an inactive thyroid since 1968 when she worked as a histologist with radiation. Terry has taken synthroid since then. However, 3 years ago, Terry started to eat Organic sunflower seed butter on Organic bread and the Celenium has restored enough of thyroid function that she no longer has to take the synthroid every day. Terry skips two days a week

          • Wendy Allen

            Zinc/Se/enough iron/probiotic may convert T4 to T3 for the thyroid hormone. Se may help stop antibodies to the thyroid. Gluten (wheat/barley/rye/oats/corn/small amount of rice) may make antibodies to the thyroid.

          • Just curios , does your wife take iodine as well ? This is an interesting issue for me.

          • Peter R. Mare

            Hi, I think I replied to this question on another post you made. Traditional Chinese Medicine as performed by an Oriental Medicine Doctor has been our primary health care provider for the last 13 years. We eat as much Organic as we can, supplement with Ubiquinol. Nuts .com is another great mail order site for Organic products. We also get quality products from pure formulas dot com. free shipping We get Natures Way: Niacin, Selenium, & Krill Oil

          • Peter R. Mare

            No, Terry does not take iodine. Organic Sunflower seed butter from Once Again. We use the natural, unsalted.

    • Julot Julott

      Raw tubers can be rapidly hard on the gut, they are not ripe fruits~
      Small amount is probably fine on a healthy gut~

      • angelica

        I’ve read this of raw Maca. Raw foodists praise raw Maca powder… It’s native to Peru and the people who’ve farmed it for many generations will not eat it that way…they cook it first. Gelatinzed Maca is cooked at a low temperature…less vitamins maybe but more bio-available and easier on the tummy.

  • SandraLouise


    • Kitsy Hahn

      Not moi!

      • Wegan


        • Kitsy Hahn

          Yeah, but I’m cute. :-P

          • Wegan

            Pretentious, moi?

          • Kitsy Hahn

            So you’re asking if YOU are pretentious? Um, sure! :-D

    • dogulas

      Based on how the microwave cooks things, it’s closer to boiling than baking. Boiling from the inside. Probably best, nutritionally, to not over-microwave them though to the point where they’re drying out. But I do it anyway a lot of the time. Nearly dried microwaved sweet potatoes are one of my favorite foods.

      • Terry

        I’m curious about the microwave thing. I’ve always been somewhat on the fence as to whether it is a safe or healthy way to cook. I do use a microwave occasionally but tend to steer clear of them whenever I can. Do you think this is unfounded? Do you know of any vids that discuss microwave safety? Has Dr. Gregor ever addressed this?

        • dogulas

          Everywhere I have read, concerns are totally unfounded.

          Microwaves work by hitting and spinning water molecules. That’s all. So they get hot and warm the surrounding food.

  • Martha

    I’ll often make a pudding with a sweet potato or a butternut squash by boiling it in one or two inch chunks and putting it, skin and all (best to scrape off the skin from butternut squash’s skin with a spoon, though) in a blender with a cup or so of pitted dates. When it cools in the fridge, it thickens, depending on on how much liquid from the boiled water I added. To give it a gel-like texture, I sometimes add a little psyllium husk powder to the blender- half a tablespoon seems to be the right amount- but this is optional. It’s very easy to make.

    I’d like to suggest that another tab be added to this site where people can share their favorite recipes.

    • Carol J

      Thank you!

  • Arjan den Hollander.

    Ahh juk!!!
    I dice my sweet potatoes then boil with quinoa and oats.
    This skin story does not sound appealing at all!
    10 times huh? Phew.

    Ahh well lets give it a try tomorrow :)

  • Thanks Dr G! Any chance you have a data summary on the acrylamide levels of sweet potatoes based on their cooking method (Fried vs Baked vs Nuked vs Boiled etc)?!

  • cyndishisara

    Is it not a fact that cooking inactivates protease inhibitors in sweet potatoes?

  • fred

    I boil my sweet potatoes and then mash them with some cinnamon, ginger and ginseng. Is korean ginseng any good?

  • cyndishisara

    It is also true that fermenting sweet potatoes converts beta carotene to retinol (active Vitamin A). I wonder what it does to protease inhibitors?

  • bkcham85

    Is there any information on what pressure cooking does to the nutritional value of the sweet potato.

    • mitch

      I’d like to know also as I just about pressure cook/steam everything. 4-5 min and they are DONE!!! I mix with curried chickpeas and I’m in heaven

  • kim

    I usually cook mine in my Instant Pot pressure cooker. They’re done in 12 minutes. How does pressure cooking compare with boiling?

  • MAbe

    In your video you mention “Carotenemia” and babies having a yellow nose as a result of eating too many carrots. Is the nose the only part of the skin that gets a yellowish tint? My little granddaughter (16 months) has a very pronounced yellow tint all over her body (not her eyes). She has been like this for at least a year . My daughter insists that it is because she eats carrots everyday. I am concerned but my daughter believes that as long as her eyes do not have a yellowish tint (signs of liver problems?) she is ok. Is this true?

    • Neil

      I remember two instances that would lead me to believe your sister is correct. A girl I knew in college told me that she had gone on a carrot kick, eating bags a day for an extended period of time. Her palms turned orange she said. In addition, a neighbor of mine was juicing pounds and pounds of carrots a day. I don’t recall how long he had been doing it, but at least a year from what I remember. He had an unmistakeable orangish/yellowish hue to his skin. This seems to be a common side effect of eating large quantities of plants with high levels of beta carotene.
      Eating too much Vitamin A is only an issue if you eat too much preformed Vitamin A, which we get from animal products (e.g., cod liver oil is really high). BUT too much of provitamin A carotenoids (such as the betacarotene in colored fruits and veggies) is not associated with any health issues, except having skin like John Boehner after an application of spray tan.
      See the “Health Risks from Excessive Vitamin A” section in this informative site:

      • Brenda

        I think you’re referring to my sister :). In college she was eating bags of carrots a day and the palms of her hands turned orange.

        • Neil

          If she went to Miami University of Ohio then I just may be! :)

          • Brenda

            Ah alas – this was while she was in Arundel, England. Good university – Miami, Ohio.

  • Jon Rosenbaum

    I have been watching your videos for about 1.5 yrs now and they are the most wonderful source of information on selective topics and in the right time span. Thanks Dr Greger for your continuing efforts. I look forward to watching them every day with a zeal that goes off the scale.

  • Laura Henderson

    I pressure cook them, I think that’s prob about the same as boiling but faster.

    • Arjan den Hollander.

      Faster & hotter, water boils at higher temperatures when the pressure is higher.

      • cyndishisara

        Exactly! PV =nRT. If you raise pressure you raise the temperature. Raising temperature in an aqueous environment is so what does this do?

        • Arjan den Hollander.

          I dunno was wondering that myself :)
          Does it liberate more or does it start to break down the good stuff at higher temperatures.

          • cyndishisara

            In the case of sweet potatoes heating must denature the protein making protease inhibitors inactive or unavailable. Only raw sweet potatoes would give cancer inhibition.

            Different cooking methods would most likely decrease availability pressure cooking ( which I use frequently) would be worse than boiling.


          • cyndishisara

            In their analysis protein loss was probably do to leaching. I wonder why they assume people throw the water out! The way they do things is so annoying! Same is true of the Vitamin C leaching.
            About heating and inactivation of protease inhibitors I have only found thus far this:


          • Arjan den Hollander.

            Only raw sweet potatoes would give cancer inhibition.

            That is assuming there is only one pathway. Those gene activation charts alone suggest there are at least tens if not a few hundred.

          • Dr. Flora

            Fermented potatoes, like fermented cabbage, carrots and other cruiferous veggies, are anti-cancer.

          • cyndishisara

            I agree Doctor Flora!! Fermenting sweet Potatoes actual produces biologically active retinol.

          • cyndishisara

            I agree!! Fermentation if done correctly reduces oxalates, phytates and other anti-nutrients. Furthermore, biologically active coenzymes can be produced such as retinol, and coenzyme b12. Having the correct starting materials bacteria and food sources are the key.

  • B

    Love this vid and it just so happened that I made an excellent raw sweet potato salad yesterday! In response to others wondering about how to eat them raw. I use the “shredder” blade on my food processor or you can use a hand one, that quickly gives you nice julienned type shreds, skin and all. I also shred some carrots and sometimes a little daikon radish, add some defrosted green peas, cilantro, green onion and crushed garlic. Dress with a wee bit of sesame oil, rice vinegar (or lime juice) and tamari. I also add ground white pepper and finely sliced hot chilis…if you like spicy ;) Toss the mix and let it marinate in the fridge for a half hour or longer. Very yummy and it will last a long time in the fridge. I’m having some for lunch right now that I made yesterday!

    • Brenda

      I may try this minus the oil. I had daikon radishes for the first time and this would be a good way to include them.

    • Dr. Flora

      Once you add the oil, it’s no longer alive. Clogs up the pores of the surface of the potato and it dies.

  • Martin Schofield

    Interesting to see the microwave option …after investigating my family no longer uses microwave … apparently molecular structure is altered hindered normal metabolic action. It would be great to see a video or even a series of videos on harmful effects of microwave ovens. They used to be banned in the Soviet Union apparently and the swiss cancer study remains pretty well hushed up.

    • Thea

      Martin: I *highly* recommend you check out the following link/page. It is a good way to learn how to distinguish the myths from the facts when it comes to microwaves. I can understand where you are coming from. The microwaves myths are repeated so often on the internet, it is hard not to believe them. Do yourself a favor and give the following page a good look.

    • Neil

      Actually, Martin, according to the study in this video, microwaving is the best way, on average, to cook veggies, and save (or even increase in the case of carrots and celery) their nutritional content.
      Boiling and pressure cooking (i.e., wet methods) were considered the worst on average because many of the nutrients leach out in the water. So, I am assuming, based on this video, that microwaving is the best–or at least not the worst–method to cook a sweet potato (I microwave all of my potatoes–easy peasy).
      As to safety of microwaves, there does not seem to be anything to worry about if the seal and hinges around the door are clean, allowing for a tight seal, and one doesn’t microwave plastic that is in contact with food. But to be safe, one shouldn’t stand directly in front of the microwave oven while it’s in operation.

    • val

      Microwaving is just a *different way* to heat up foods…foods may change due to heating whether boiling, roasting, etc…but microwaving doesn’t alter them any differently than boiling, roasting, etc. Just my 2 cents.

    • Brenda

      I was at a talk by T. Colin Campbell. Afterwards I got in line and asked him about microwaves. He didn’t mention them during his talk but he was blunt – no. I got rid of mine immediately and haven’t used one since. I didn’t ask him to elaborate on why he felt that way – long line, lots of people waiting to talk to him. He’s been in science a long time and I have other ways to cook food so I just decided not to use it.

    • bob

      I stopped using a microwave for food…except to nuke old CDs/DVDs…only takes a second…don’t breathe the fumes. If god wanted us to use microwaves…there would be natural microwave appliances in the forests. ;-)

  • Psych MD

    I wonder if this could be the reason the protein survives. Saw it on a site discussing raw food toxins:

    “Sweet potato shows trypsin inhibitor activity. That means it contains an enzyme inhibitor that blocks the action of trypsin, an enzyme that digests proteins. The trypsin inhibitor prevents the digestion of protein. Sweet potatoes with higher protein levels have more of the trypsin inhibitor. This makes raw sweet potato difficult to digest. The trypsin inhibitor is deactivated by cooking.”

  • So, those sweet potato chips are bad for you! Unless they’re baked, of course.

  • val

    Yeah, baby! Eat those sweet ‘taters! Have always known to eat the peel…and now I will make sure I boil them…I was microwaving so as not to heat up the kitchen in the SW Florida heat and save a/c costs…but I can easily *gently* boil them without too much added heat in kitchen. THANK YOU, Doc for all you do to help us!

  • Martha

    Dr. Greger, you seem to conflating boiling and steaming. Do steaming and boiling have the same effect on the nutrients in sweet potatoes? It’s not clear from the video.

    • Neil

      Watch this, Martha:
      Based on the rational and results in the video (which doesn’t mention potatoes), steaming it seems would be better. (Boiling and pressure cooking veggies are apparently the worst methods to cook veggies.) When you boil something, it is surrounded by boiling water, obviously. As the veggie cooks, nutrients are more easily lost into the surrounding water in which the veggies is enveloped. Steaming, however, would cause less nutrient loss, as the steam is not as heavily in contact with the veggie as boiling water.

      That said, the video indicates that cooking carrots, onions, and celery in a soup would be a good way to get the most out them, nutrient-wise.

  • typical LIBtard fake docter planted by OBummer.

    TEA PARTy 2016

    • Neil

      Looks like the trailer park got internet.

      • Arjan den Hollander.

        Are all trailer girls like Ronda Rousey?
        Saw her finish a fight in 15 seconds.
        Guess a diet of rabid raccoon meat?

  • MilkisPoison .

    Sorry, I’m a bit squeamish about eating the skin unless I know what the potato was grown in. “Organic” gardeners may use feces, blood or bone meal, etc. as fertilizers.

  • b00mer

    Interesting to hear the official word on the glycemic index. I’ve always been a bit of a snob when it comes to baking rather than boiling. Perhaps for savory applications I might boil if in a hurry, but for sweet potato casserole, boiling would be sacrilege. :)

    One of my favorite easy peasy ways to eat sweet potatoes (which does just fine with boiling):
    Throw a couple cooked sweet potatoes in a bowl
    Add a big spoonful each miso (I use white), mustard (any kind), & nutritional yeast
    Mash and mix together

    It’s so good I can eat it with a spoon. It’s great tossed with pasta for a quick sauce and a nice light dinner. Also good as a mayo replacement/all purpose binder. I first made it when I was making the Engine 2 “Raise the Roof” lasagna recipe and I wanted to jazz up the plain sweet potato layer so I added just what I remembered as the key players I’ve seen in various “mac n cheeze” recipes.

    Another favorite of mine is simply a baked sweet potato blended with cocoa powder added to taste. If using baked potatoes, you don’t need to add any additional sweetener.

    • Brenda

      Yum. These all sound great. I did something similar with a bowl of steamed cauliflower that start out as a dip – just ate a bowl with a spoon.

      The cocoa with the sweet potato – isn’t that iffy as sometimes my sweet potato is very sweet, other times not so much.

      • b00mer

        Sure, at times I have added a bit of maple syrup, but typically I don’t feel that it needs it. It could depend on the time of year, quality of produce, etc. And of course cooking method. Also depends how chocolately you like it – if adding quite a bit of cocoa, there comes a certain “saturation point” where you use up all the sweetness from the potato and need to bring in reinforcements. :)

    • salley

      what about the skins? do you use those in your recipe

      • b00mer

        Hi Salley, personally I don’t eat the skins. They just weird me out :) But plenty of people do. In this case, I take what Dr. G says at 2:28 to heart.

        If you’re open to including the skins in the recipe, I’m afraid I can’t offer any insight into how it would turn out. If I imagine including them, I expect the skins would be tougher and with a more robust flavor than a white potato skin. But as I’ve said, I’ve never actually tried it.

        Perhaps someone else can give us some details on how the skins affect the flavor and texture (when mashed)? Do they mash up as easily as white potato skins or does it have to go through a processor?

    • Thea

      b00mer: Awesome ideas. Thanks for sharing!

      FYI: The first idea, with the miso, mustard, and nut yeast was one of those small-world moments for me. I just the night before I ready your post, I had gotten the book, “Happy Herbivore Light & Lean” and was flipping through it. On page 141 was a recipe called “Golden Dressing” which is primarily those same three ingredients. (Though there is also a smidge of sweetener and lemon.) Now I’m doubly-excited to try it.

      • b00mer

        I’ve never thought to try it as salad dressing – will have to do that! Mine would have to be thinned out a bit, so I could definitely see adding some lemon juice to it. Btw, have you made “squash colombo” out of Cooking Under Pressure? Just tried it for the first time a few weeks ago – butternut squash, onion, tomato, cumin, coriander, turmeric, and lots of jalapeno and ginger. I added in frozen green beans and peas for some body and color. It’s described as a “sri lankan-carribean” curry. Very tasty and even my resident squash/ginger-hater really liked it :)

  • Ben

    Dear Dr.,

    Does the same rule apply to other starchy orange-fleshed vegetables, like butternut squash? Should I try to boil or microwave squashes like sweet potatoes, instead of baking them?

    Thanks for all the information!

  • Tobias Brown

    I compared the nutritional profile of baked vs boiled sweet potatoes in Cronometer and baked shows higher nutrient levels almost across the board. Anyway. They taste as good boiled and the skin is more palpable boiled, IMHO. Also, the calorie count is a bit less for boiled. Baking seems to give a sweeter taste, especially after they’ve rested a day or two in the frigo (at which point very sweet syrup begins to ooze out, offer a wonderful dipping sauce :).

  • Rivka Freeman

    Really glad Dr Greger is so thoughtful to tell us “eat potatoes made any way except fried” cause I don’t like boiled potatoes or carrots. I hate them in soup or cholent. I like everything vegetables, grains and bread made soft and mushy on the inside and hard crusty and crunchy on the outside.

  • William Dwyer

    I’ve always made a distinction between sweet potatoes, which are beige colored, and yams, which are orange colored. Dr. Greger calls both tubers “sweet potatoes.” I prefer yams, not only for their superior nutritional value, but also because they’re sweeter.

    Yams (and sweet potatoes ;-)) cook really well in a pressure cooker on high for 10 to 15 minutes. Cooking them this way softens the flesh and the skin, which literally falls off. Cutting them into quarters lowers the cooking time. They also go really well with collard greens. I cook both together in the pressure cooker.

  • Mary J

    What about cooking them in a Crockpot?

  • John Mclaren

    Actually I understood sweet potatoes to be basically acrylamide free when cooked at any temperature, quite unlike white and yellow potatoes, toasted/baked grains, bread, toast, coffee, cereals, dutched cocoa, brown rice syrup, snack bars, olives (oddly enough), etc.

  • Alianna

    I thought you couldn’t eat the skin on sweet potatoes.

  • Guest

    The “Cancer Risk from French Fries” video link above doesn’t work; it contains colons instead of slashes.

  • srut

    This is my first time posting and I would like to have my posts read
    Susan How so I change my name?

  • Hila Eliyahu

    What do you think about this article claiming that plant sources of vitamin a lead to deficiency in that vitamin?

    thank you.

  • Claire Elizabeth

    Hi Dr. Greger, I was wondering what your opinion is on the incredibly high vitamin A levels in foods like sweet potatoes, carrots, leafy greens, pumpkin, butternut, etc. I really enjoy eating all of them, but am worried about consuming too much vitamin A. I try to get at least one cup of raw lettuce/leafy greens a day, and with having other sources of vitamin A it just adds up so quickly. Before I know it, I’ve already consumed over 1400% daily value for vitamin A!
    I do not, however, consume any preformed vitamin A, because I’m vegan and also don’t take supplements with vitamin A in them. Unfortunately though, practically ALL non-dairy milks on the market have vitamin A palmitate added! :(
    I hope I’m not coming across as obnoxious or overly concerned, but the amounts of vitamin A a whole-foods-plant-based vegan can easily and unknowingly consume are quite high! I really really hope to hear back soon!

    P.s. I absolutely LOVE your videos! I’m a bit of a nutrition nerd myself, and these videos kept me thoroughly entertained on an eighteen-hour-long road trip! Keep up the great research work Dr. Greger!

    -Claire Elizabeth

  • Mihaela-Carmen Badic

    Thank you so much Dr Greger.

  • RKent

    I boiled purple sweet potatoes and was shocked to see the boiling water turn dark purple. All of those nutrients lost! Is this really the best way to cook them? Did the study account for nutrient loss in the boiling water?

  • cyndishisara

    I am beginning to wonder if pressure cooking is indeed unsafe. I have been alerted to the fact that the Milliard reaction starts at 250 degrees F and pressure cooking 15psi brings the temperature to 250F. Just the right temperature for acrylamide production!

  • Tobias Brown

    I started boiling after baking — based on this video. Then I got an Oster steamer. This changed everything! The ease of preparation and the better taste of the final product convinced me that this will be my prefered method regardless… Anyway. I reviewed the databases and didn’t find any nutritional profiles on steaming for sweet potatoes, only baking and boiling. So, is steaming closer to baking or boiling? I’d say baking. With this question in mind, I reviewed side-by-side comparisons of baking vs boiling and baking consistently seemed to provide a better nutritional profile. This contradicts the message of this video. Also, do we care about the glycemic index really? I thought that index was next to useless. (The video cites this as well as a reason to boil vs bake.) Though it softens the membranes by boiling, aren’t we maybe leeching nutrients? Does some of the sweetness that makes the potato so tasty go down the drain? This Oster steamer is an amazing machine. The taste, texture, and consistency are impressive.

    • Thea

      Tobias: Thanks for the tip on the Oster steamer. I’m always on the lookout for helpful kitchen gadgets to make cooking easier. Thanks!

      • Tobias Brown

        This $30 steamer Oster unit has displaced FOUR of my formerly essential kitchen cookers to the storage area: Tiger rice cooker, Instant Pot pressure cooker, Crock-Pot slow cooker, and stove-top pot steamer. Cooks rice to perfection. Works as fast as pressure cooker because steam begins in 30 seconds whereas the pressure cooker takes some time to build pressure to cook. Oat groat cooks just as well there versus 3.5 hours in the pressure cooker… etc etc. Something about how the steam provides a uniform and surrounding heat that renders things so well. I have noticed the nutrient profiles often don’t give breakdowns for steaming (it’s either baking or boiling) and steam times guides online are rather patchy.

        • Thea

          Tobias: re: replacing 4! appliances. That’s really impressive. It’s definitely something to consider. Too bad it is plastic. I may break my rule about cooking in plastic. After all, I broke down and got a Vitamix which has the plastic container. So, I’m open to plastic when the convenience factor just can’t be ignored.

          Thanks again for sharing. I’m super intrigued.

    • Thea

      I forgot to ask: I can’t tell if the steamer is plastic or glass. I was looking at this one:

      Is that hte model you have? Can you say what the baskets are made of? Thanks.

      • Tobias Brown

        This one model number off the one I purchased,

        I recall that the plastic is safe. But don’t quote me on this.

        • Tobias Brown
          • Tobias Brown

            But just because it’s non-BPA, does this mean they didn’t use something worse that’s not on the radar yet? Hmm. It’s so hard to know these things.

          • Thea

            Tobias: Exactly! I have read articles that say that the chemical they use to replace the BPA is likely as bad if not worse. So, the label of “BPA-free” does nothing to allay my concerns. Too bad it’s not glass!

            If you are interested, here is an article on the topic of the safety of bpa-free plastic. I’m not an expert myself, so I don’t know how valid this article is.

          • Tobias Brown

            Article “Sent to Kindle” for offline Paperwhite reading (another amazing technology). No really, I’d like to get to the bottom of this plastic issue… I imagine there’s a higher end product out there that’s 100% safe (though I’m not aware of any presently). (The nice thing about this unit is that it starts steaming in 30 seconds and envelopes the contents in a uniform heat..

        • Thea

          Thanks! I wanted to make sure I was looking at the same one you have.

  • cranberries_2

    I’ve recently discovered sweet potato noodles from Korea, made from sweet potato starch.
    A nice substitute for white pasta and noodles although whole food is still better for us.

  • Daniel K Morris

    Sweet potatoes were a major part of the diet of one the longest living people on the planet. The traditional Okinawa Japanese diet included over 50% of their calories from sweet potato and 5% or less of their calories from animal products. For more information on reasons why Okinawa Japanese have such high rates of centurions see the video here.


  • Rob English

    How long should you boil them – say for 1-inch cubes?

    • Joseph Gonzales R.D.

      That will lower cooking time if pre-chopping. Perhaps 15-20 minutes, or until soft will do the trick?

  • rappinronreagan

    This is a bit confusing. Sweet potatoes are not orange yams are orange. People often interchange the two but I think it needs to be clarified here because they are two different things.

    • Joseph Gonzales R.D.

      Thanks for suggestion. These studies used sweet potatoes from what I see. Yes, yams are different and I even forget their differences, but I think the point is eating sweet potatoes, yams, and other bright-colored foods is important for disease prevention. If I find studies on yams I’ll post. Thanks!

  • Stephen Belter

    Any suggestions for the best way to cook them if we have sensitivities to salicylates? My levels seem to rise like crazy after eating them as they are reported to be very high in salicylic acid.

  • Julien Brown

    What should I do? Eat conventionally grown purple sweet potato, or eat organic sweet potato?

    • Joseph Gonzales R.D.

      Both! Organic is probably better but don’t let that stop you from eating conventional.

      • Julien Brown

        I have the choice of cooking either one. Which is greatest for my health? Do pesticides outweigh the benefits of switching from regular sweet potatoes to purple yams? From my understanding, these purple yams are from Asia, they are not the sweet potatoes Dr. Greger is suggesting. Thanks for your swift answer by the way.

    • TheGood

      do you really need anyone telling you which one is better or healthier!??
      how can you possibly doubt or believe that vegetables, fruits, nuts or seeds that are sprayed with chemicals could be harmless or as good as chemical-free or Organic !!!?????

  • Cynnthea T

    I would much rather read the information- very frustrating that I have to waste time watching a video!! good info though. All I wanted was the info on the skin!

    • Thea

      Cynnthea T: re: “…rather read the information…”
      No problem. Just to the right of each video is a “Read Transcript” button. After you click the button, the transcript will appear below the video.

      Even though I enjoy and watch the videos, I sometimes like to go back and read the text and/or read the text while the videos are rolling. You are definitely not alone in the desire to have the information written. Happily, NutritionFacts made that feature a priority a long time ago.

  • nancy campbell

    Does roasting vegetables contain carcinogens, as in grilling? I love roasted vegetables, but if it’s unhealthy I prefer an alternative method.

    • Joseph Gonzales R.D.

      Nope. The carcinogens cannot form on plants like they do on meat. Here is a great link on more about these HCA carcinogens.

  • Katherine

    I’m a little hesitant about boiling sweet potatoes. Maybe you could help me?
    They always seem to take longest to cook this way and I end up cutting them up because they are still pretty hard. I’ve also heard that cooking foods for a long time decrease nutrients. Boiling, I know, is notorious for decreasing the sensitive vitamin C in many vegetables. Don’t a lot of the nutrients get poured out with the water used to cook the vegetable/tuber?

  • Kenji of suggested soaking in hot water (between 135F and 170F) for at least one hour prior to cooking to allow enzymes to turn the starches to turn into sugars. I tried it and indeed the result seemed sweeter. Are you aware of any scientific research to back up this procedure?

    • Joseph Gonzales R.D.

      How interesting. Is it more palatable when sweeter? Gosh I am not aware of other research other than the ones listed in the “sources cited” section. If I find anything groundbreaking to add to the discussion I will.

  • Gina R.

    Thank you for another amazing fact Dr. Greger. x

  • Try sweet potato salad, but par-boil the potatoes first as they get too mushy. I also enjoy sweet mashed potatoes.

  • GEBrand

    I am interested in whether this boiling-is-better cooking method would be the same when applied to other orange-fleshed vegetables such as butternut/kobacha/acorn winter squash and carrots?

  • Raemino

    Thank you Dr.Greger ! I have a question about carotenemia : I usually eat much sweet potatoes (approximately 1kg per day), i want to know if i could have carotenemia with this quantity of sweet potatoes ?

    Thank you in advance for your answer !

    • Cathleen_NF_Moderator

      Hi Raemino- I couldn’t find an exact answer to how much sweet potato one would have to eat to change skin color. I would guess this varies somewhat depending on your skin pigment and how much you weigh along with the amount of sweet potato. I think a good guide is if you see you are turning orange, decrease the amount you are eating. Your skin turing orange is a sign your body is getting more beta-carotene than it needs. Hope that helps.

  • Adalin

    Hey, if eating a bunch of beta carotene will make your skin orange, what will if eating a bunch of beta carotene will make my skin orange, what will eating a bunch of chlorophyll do? Will I turn green?

  • Adalin

    Sorry, I meant, what will eating chlorophyll do to your skin?

    • Cathleen_NF_Moderator

      Chlorophyll supplements can stain your skin green and turn your stools green (and aren’t recommended anyway…see today’s video and discussion) but as far as I can tell from reading, chlorophyll won’t turn your skin green. You can eat your greens without worrying about looking like Kermit.

    • payoung

      I’m not sure if eating chlorophyll will do anything to the skin but in this study they used topical chlorophyll along with phototherapy and it helped acne.

  • ignacio

    Hi Dr., I’ve become abit addicted to the information shared here. thanks!! :)

    that being said, I work as a chef and I’m utterly curious as to what is he best way to cook (from a nutritional point of view) virtually every food there is. grains, legumes, nuts, seeds, animals. Is there any study you can refer ? any book to recommend?

    • RalphRhineau

      Try my response to Sarah Audrey a couple of posts above for a link to best cooking methods the good Dr made a while back.

  • nomij

    are air fryers (latest craze that use only a spoonful of oil in food preparation) healthy or the opposite?

  • So what if you use a little olive oil or vegetable oil and then bake them? Is that very similar to deep frying?

    • RalphRhineau

      It’s at least somewhat similar due to the smoking point of oils. Forced to choose between frying and oiled roasting I’d choose oiled roasted because one ends up with less oil retained in the food. Better still is to roast without using oil.

      If you’re roasting without oil (which is what I do), the temperature of the food us kept lower because the water in the food boils/evaporates at 212°F/100°C. It’s hard for the food to rise above that temperature as long as the food has moisture.

      When you apply oil to the surface, you enable higher more damaging temperatures to be present in the food because the oil can sustain temperatures on the order of 350°F/175°C. The oil however will thermally decompose and form carcinogenic compounds before it boils away in contrast to water.

      Hope this helps.

  • D. A.

    Ask the Dr. Q: Acrylamide update in the works? Wikipedia: “…Acrylamide is easily absorbed by the skin and distributed throughout the organism; the highest levels of acrylamide post-exposure are found in the blood, non-exposed skin, kidneys, liver, testes, and spleen. Acrylamide has also (besides tumor growth) been found to have neurotoxic effects in humans who have been exposed.” So potato chips are not to be touched, literally; but: “…Laboratory research has found that some phytochemicals may have the potential to be developed into drugs which could alleviate the toxicity of acrylamide.” Could consuming a WFPBD with super high antioxidant content offset the amount of acrylamide from a homemade baked good or sweet potato roasted above 248 f?

  • Joseph Connelly

    Is it possible that Donald Trump us suffering from Carotenemia?