best method for cooking sweet potatoes

Image Credit: Avital Pinnick / Flickr. This image has been modified.

Is it Better to Bake, Boil, or Steam Sweet Potatoes?

I previously talked about the cancer fighting properties of sweet potatoes (See Anti-Cancer Potential of Sweet Potato Proteins) and what would happen if you centered your diet around them (The Okinawa Diet: Living to 100). It seems that the only potential downside to eating too many sweet potatoes is that you could get yellow palms (or nose as you can see in the video, The Best Way to Cook Sweet Potatoes), a harmless condition called “carotenemia.” Caused by elevated levels of beta carotene in the blood, it was first noticed a century ago when carrots were introduced into infant diets. It’s treated mostly by just reassuring parents that it’s harmless, but if we don’t want our child’s nose to be yellow, we can decrease their beta carotene intake and in a few months it will be gone.

When picking out varieties at the supermarket, the intensity of the yellow or orange flesh color of the sweet potato is directly correlated to its nutritional content, so the more intense the better. Though if you really want intensity, sweet potato varieties don’t just range from white to yellow and orange, but from pink to deep purple. The natural pigments that cause these colors may have special anticancer effects.

What is the best way to cook sweet potatoes? Boiling may actually retain most of the antioxidant power of sweet potatoes, compared to roasting and steaming. If we compare baking to boiling microscopically, boiling helps thin out the cell walls and gelatinize the starch, which may enhance the bioavailability of nutrients. At the same time, the glycemic index of boiled sweet potatoes was found to be about half that of baking or roasting, so boiled sweet potatoes give us less of a blood sugar spike.

Make sure to keep the skin on, though. The peel of a sweet potato has nearly ten times the antioxidant power as the flesh (an antioxidant capacity comparable to that of blueberries). However, the peel’s nutrition really takes a hit when baked, which wipes out over two thirds of the antioxidants, whereas microwaving or boiling are comparatively much gentler. The same is true for the rest of the sweet potato. Baking can also cause an 80% drop in vitamin A levels, twice as much as boiling. Therefore, from a nutritional standpoint, boiling rather than baking should be recommended for cooking sweet potato.

Boiling may theoretically be best, but sweet potatoes are so incredibly healthy that the actual best way to prepare them is whichever way will get you to eat the most of them! The exception is deep frying, which can lead to the formation of acrylamide, a potential human carcinogen.

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.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of DeathMore Than an Apple a DayFrom Table to Able, and Food as Medicine.

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.


68 responses to “Is it Better to Bake, Boil, or Steam Sweet Potatoes?

Comment Etiquette

On NutritionFacts.org, you'll find a vibrant community of nutrition enthusiasts, health professionals, and many knowledgeable users seeking to discover the healthiest diet to eat for themselves and their families. As always, our goal is to foster conversations that are insightful, engaging, and most of all, helpful – from the nutrition beginners to the experts in our community.

To do this we need your help, so here are some basic guidelines to get you started.

The Short List

To help maintain and foster a welcoming atmosphere in our comments, please refrain from rude comments, name-calling, and responding to posts that break the rules (see our full Community Guidelines for more details). We will remove any posts in violation of our rules when we see it, which will, unfortunately, include any nicer comments that may have been made in response.

Be respectful and help out our staff and volunteer health supporters by actively not replying to comments that are breaking the rules. Instead, please flag or report them by submitting a ticket to our help desk. NutritionFacts.org is made up of an incredible staff and many dedicated volunteers that work hard to ensure that the comments section runs smoothly and we spend a great deal of time reading comments from our community members.

Have a correction or suggestion for video or blog? Please contact us to let us know. Submitting a correction this way will result in a quicker fix than commenting on a thread with a suggestion or correction.

View the Full Community Guidelines

  1. Are you concerned with the science claiming that sweet potatoes have a protein structure that is not completely broken down in the human body, and in some people this undigested protein might therefore cause autoimmune issues, allergies? Yes, there is a benefit to undigested sweet potato proteins, as one of your past videos claimed, but what about folks with autoimmune issues and or allergies/intollerances to undigested food proteins? The cons might not be worth the benefits?

      1. Sweet potatoes contain undigested proteins. Dr. Greger had done a video on this in the past. Seems like it could be troublesome for some people to have undigested proteins floating around there body. Hopefully he chimes in on this one.

        1. The last 4 days I added less than half a sweet potato back into my evening pot of boiled veggies.
          I removed them from my diet when I noticed an autoimmune issue of a swollen finger and red warm ears.
          So far I haven’t noticed a problem, but this time I removed the skins. I do like them and sure didn’t want to give them up. Especially when they’re on sale at .33 a pound for Thanksgiving..:)

          1. A sign not to eat them? Goes to show, so many foods in the plant kingdom can cause problems with some people’s bodies (soy, flava beans, wheat, tomatoes,……..)

            1. I also cut way back on tomatoes. I used to add tomato paste to my veggie soup..Grr
              Now I pay way more attention to what makes my ears warm and red after eating something.
              Years ago I had no idea there might be a food related problem.

            2. Some people may have a problem with some of those foods, but a lot of people do not. And if one bothers them there are plenty more to take their place !! Myself i do not have a problem.. I eat all the foods you mentioned and at 60 i am healthier than i have ever been. Animal foods are known to cause all kinds of problems and i choose to have none.

        2. Good point. Proteins of really any food may cause someone trouble if they are allergic. The most problematic foods that can trigger pain tend to be: dairy, eggs, meat, nuts, nightshades, citrus, added sugar, sulfites, caffeine, alcohol, and apples and bananas. To read more about the paper click here.

          I will say, I had one participant in this study react to sweet potatoes but not regular potatoes. She had no trouble with other nightshade vegetables like peppers or eggplant. It was odd. That was the only time I had heard someone having a bad reaction.

          1. Look into Oral Allergy Syndrome. I ended up going through allergy testing yet again after having what seemed like random reactions to food (throat would start to swell) even though my whole life I’d never had food allergies. Turns out those of us with long standing nasal allergies can develop oral sensitivities because proteins in pollen are very similar to protein in fruits, vegetables, spices and nuts. The most common one is birch pollen and raw apples, which is the first one I developed. Allergist gave me a rather scientific article on this showing how research had identified certain reproductive proteins in apples as being similar to certain birch pollen proteins. The article goes on to say certain proteins are only generated when the plant is under stress and maybe the widespread application of agricultural chemicals is adding to the stress. Sometimes the proteins can be altered enough with cooking so the immune system isn’t triggered. While certain foods trigger an almost immediate response in me, others seem dose dependent. And sadly even though I’ve been vegan for years I occasionally end up with a new food on my avoidance list.

          2. Joseph, is it true that the Okinawans ate yams and not sweet potatoes? Apparently what they ate was a true yam, no? Also, wondering how long you boil your sweet potatoes for?

            1. I am not sure. I always get these mixed up and the last time I check our superstar volunteer, Thea, made a post further down to help clarify. However, I have no idea what the “exact” food (yams or sweet potatoes) they eat in Okinawa. Anyone? Anyone? Bueller?

              We’ll find out! Thanks, Leslie

      2. http://www.hopkinsmedicine.org/news/media/releases/low_carb_higher_fat_diets_add_no_arterial_health_risks_to_obese_people_seeking_to_lose_weight

        “Among the researchers’ other key study findings, to be presented separately at the conference, was that consuming an extremely high-fat McDonald’s breakfast meal, consisting of two English muffin sandwiches, one with egg and another with sausage, along with hash browns and a decaffeinated beverage, had no immediate or short-term impact on vascular health. Study participants’ blood vessels were actually less stiff when tested four hours after the meal, while endothelial or blood vessel lining function remained normal.

        Researchers added the McDonald’s meal challenge immediately before the start of the six-month investigation to separate any immediate vascular effects from those to be observed in the longer study. They also wanted to see what happened when people ate a higher amount of fat in a single meal than recommended in national guidelines.

        Previous research had suggested that such a meal was harmful, but its negative findings could not be confirmed in the Johns Hopkins’ analysis.”

    1. Gotta pipe up here and mention that if you want the benefits of sweet potatoes but worried about the digestion issues, a great option is fermentation which partially pre-digests foods PLUS adds pre- and probiotics to your microbiome. You can ferment them either raw or cooked, quite yummy, the internet abounds with info!

      1. Fermentation is awesome in so many ways. I completely agree with you Charzie. There are some foods that are very healthy, that I , uh, don’t, uh, quite find that tasty. Like raw kale, raw mustard greens, raw amla, raw Alexanders, raw lovage, and some other vegetables. They retain their antioxidants and enzymes. It can make the nutrition in food more bioavailable, and it can decrease oxalates. That’s why people have been doing it for so long.
        John S

    2. I am not concerned with autoimmune issues but I wish to clarify that the Okinawans do not consume sweet potatoes. They use to consume large amounts of Japanese Yams which appears to have been healthy in addition to the rest of their diet. Sad to say the younger generations are moving toward the Western Diet and getting the same illnesses as in the US the more they modify the traditional old diet.

      1. YES THEY DO… They eat lots of “Okinawan Purple Sweet Potatoes”.
        Which contain more nutrition than other Sweet Potatoes.
        Have You ever been there? No You Haven’t have you?
        Do proper research, Then You won’t talk RUBBISH… Muppet Brain.

    3. those with autoimmune issue know better than to eat sweet potatoes or in fact any other foods that causes flare up or problems, so don’t bash the author for giving you an FYI about how healthy sweet potatoes. It’s the same thing with IBS sufferers, they aren’t going to eat eggplant if they break out in hives

    1. Dr. Greger says whatever gets you eating more healthful sweet potatoes is really the best way to cook them! Same goes for other fruits and vegetables. Boiling is comparable to using a pressure cooker. Sure, some nutrition is lost, but it’s not a lot.

  2. I wonder if we know what the ‘sweet spot’ is when boiling them – i.e. I’m guessing that we should boil them for as ‘little’ time as possible to break down the starch but not to provide any further loss of nutrients?

    Also, any information on how slow-cooking at a low heat compares to baking?

  3. I wonder why boiling retains more nutrients in the sweet potatoes than steaming, in that aren’t both with water at the same temperature? And doesn’t boiling involve “soaking” the sweet potatoes in water, vs steaming steams the sweet potatoes?

  4. how about just microwaving? You mentioned microwaving in passing as a means of preserving nutrients n the skin, but what about the rest of the potato in the microwave?

    1. I have the same question. Im usually lazy and throw my potatoes in the microwave for 10 minutes. I wonder in general how a microwave affects the nutritional value of any foods. Maybe a good subject for a future video?

  5. This article includes “steaming” in the title, but never addresses how it compares. Is there any information on how steaming compares to boiling? It would seem it may be better than both baking or boiling, but it’s is sadly neglected :(

  6. I always make mine into oven fries. This provides the best combination of softness and crunchy texture. They have a firmness that is superior to the baby-food/pudding mushiness of boiled sweet potatoes. I serve them with homemade catsup and sriracha sauce. It is my opinion that I’m getting plenty of carotenoids when all my other food items are taken into account so I don’t have to sacrifice consummate sweet potato enjoyment for the sake of increasing vitamin uptake.

  7. Dr. Greger touched on microwaving sweet potatoes, saying it was much gentler on the antioxidants (like boiling) compared to baking. But what about microwaving compared to boiling? I like microwaving my sweet potatoes because it takes very little time and it cooks the whole potato evenly (skin and flesh) if done for 25 minutes at 50% power. So I think his title should have been “Is it better to bake, boil, steam or microwave sweet potatoes?” Which is better, microwaving or boiling? Thanks.

    1. You are so patient! I kill mine at full power for 6 minutes! LOL! They taste totally different baked whole, cut up as “fries”, grilled in foil, so interesting! I agree with doc G…whatever gets us eating them. I just pureed some with other veggies, and beans, an apple for some sweet balance, and Indian spices, into a smooth spicy hot thick soup, yum! I like options! I think we each need to invite a SAD eater to live-in for a week so we could re-educate their palates, eh?

      1. the best foil grilled sweet potatoes are the ones which come out all wet with juices when you open up the foil, it’s like natural butter.

  8. When Dr. Greger is talking about glycemic index, and blood sugar spikes, who needs to take heed? Everyone? Those pre-diabetes or with diabetes?
    I see discussions about glycemic index and limiting blood sugar spikes all over the fitness and health articles, but I’ve never seen anything that indicates why we need to be concerned about any of those if we have healthy insulin response.
    Am I missing something?

    1. They can lead to inflammation and eventually Alzheimer’s. Paleo oriented people are more focused on glycemic>diabetes>obesity>inflammation>heart disease>Alzheimer’s. There are different empases that different medically oriented groups focus on.

      1. I’m sorry John, but on the face of it, that doesn’t seem like a reasonable concern. If our body is properly regulating blood sugar how is that leading to Alzheimer’s? Over regulation? Is insulin related to Alzheimer’s? We have seen that there are indications that high cholesterol is associated with Alzheimer’s.

        1. This is why no one on this site is willing to explain a different point of view. If you try to explain it, someone will brush you off and dismiss you. Find someone else to explain their point of view to you.

          1. I’m sorry if you feel my response brushed you off. You didn’t explain your point of view. You simply stated it. My follow up questions were looking for explanation. Especially since your response started with “They” without really giving a hint what “they” were. I included to subjects in my original question, One was blood sugar spikes and one was insulin response so it wasn’t clear what you felt was leading to inflammation and Alzheimer’s. I can do more research myself but I thought I would give you a chance to fill me in and others that read this.

            My main point is I hear about worrying about blood sugar spikes almost as much as worrying about protein so I am curious about why healthy insulin response people really should care about blood sugar spikes, especially those on a general whole plant lifestyle.

  9. Ms. Greger sometimes I’m thinking you like to kitten the folks. Do you hornestly write and think about microwaving? Please, ask your stuff to do still this week this experiment. Boil one liter water and microwave one liter water, label each exactly – than use this water to watering a plant each in your office and look what will happen… it is a simple studie. If you use two different coloured bins and only you know what water is what you have a double blind study ;-)
    I guess after this experiment – you never will only mention the microwave, your stuff will remove any microwave out of the office and home… :-))
    If you don’t have the time to do it by your self, look here…..https://www.youtube.com/watch?v=iqyBWUUm8zA
    I also heard of a Oxford study back in the 90, which showed that cats feeding with microweved food (it was heated only 1 minute and served than when it was cold again) has been starved to death. while the other cats in this experiments, feed whit the same food but not microwaved lived on. Unfortunately I’m not able to find this study by internet only the mentioning… sorry, I’m sure you are the better one of research in the internet and you have the better conections… ;-)

      1. Thank you fflawpunk for your respont – do you know the writer of this article? Do you know him personal and trust him?
        Sorry, but did you ever heat a meatball for example in the microwave? I did and I was wondering why the meatball was outside stil cold but inside it was nealy hot.
        I know, not believe, the reheating or cocking by microwave is comletely a other thing then cocking normaly. Normaly cocking ist also a physical thing but not by magnetism. Have you ever though about why micrawaves have to be removed and destroid when den fontglas ist demaged? I mean, when my cooking pot is ugly, the surface destroid I still able to use them to cook my potatos – nobody will warn me about the saefty regulations.
        You migh be right whit this video… but, I made the same test when I heard first of it, years ago with my microwave – same result. This was the day when I throw away my microwave. ;-))

    1. This is also my concern. I’ve read some disturbing articles about the effect of microwaves on the cellular structure of different foods. I prefer to err on the side of caution until I know!

    2. My Grandson did this test with microwaved H2O vs Tap water to water exact same plants, for a school project. The Microwaved watered plants did poorly or died. The tap watered plants were fine and healthy. ! That was enough for me. !

  10. Guest: I have been having psoriasis for about 30 years, I use biologics to clear it, but not all the time. Question: I understand I have an autoimmune system desease. If there any foods that you are aware of that trigger psoriasis. appreciate an answer very much. Thank You JF

  11. What about sous vide? I’ve read that it provides the highest retention of vitamins versus steaming and boiling and that the pouch eliminates mineral loss thus preserving mineral content of fresh foods. Is this not the case? If it is, I’d love for NutritionFacts to touch on this form of cooking, especially since it’s becoming affordable for the home cook (< $200). Even Apple is going to carry a brand in their stores. I realize that most people associate meat and fish with sous vide but vegetables, grains, beans, tofu, tempeh, seitan and vegan yogurts & cheeses are all phenomenal prepared this way.

  12. I think the validity of many of the studies we’ve been relying on will need to be reconsidered in light of the biological principle of (nutritional) “hormesis”. For instance… “Acrylamide occurs as a natural product of cooking with high levels being detected in widely consumed food items. It has been classified as a group 2A carcinogen (probably carcinogenic to humans). Hormetic effects have been reported: “unexpectedly an inverse trend was found for large bowel cancer with a 40% reduced risk in the highest compared to lowest quartiles of known acrylamide intake” (Mucci et al. 2003a), and a decreased risk of colorectal and kidney cancers with increasing acrylamide dose (Mucci et al. 2003b).”

  13. Like many people, I like to microwave mine. It’s just easier. However what is not mentioned here is that all methods of cooking sweet potatoes can produce acrylamide. Microwaving is worse than boiling:

    http://www.ncbi.nlm.nih.gov/pubmed/17995763

    “Surprisingly, all present results showed that microwave heating not only
    induced acrylamide formation in the 2 model systems but also
    facilitated more acrylamide to be formed as compared to the boiling
    method at identical pH and treatment time… the larger the microwave power, the more the acrylamide content”

    Basically acrylamide is formed when certain sugars in potatoes are heated to high temperatures. It makes sense that a high powered microwave would generate more since the method of heating causes hot spots and a higher powered microwave would accentuate those hot spots to get the same amount of potato thoroughly cooked.

    The optimal way to cook sweet potatoes to avoid the formation of acrylamide is to keep them just under boiling for a longer period of time.

  14. This might seem like a strange question but does it make a difference if you boil the sweet potatoes whole or cut up? Anything you can do with the water afterwards?

  15. I steam ALL my veggies which I do not eat raw….there is no other way that
    brings out such wonderful flavor………
    They are cooked just until fork tender..
    Just important to keep an eye on the timer
    I would never ruin a vegetable by nuking it…….
    e.g. broccoli loses almost 100% of its nutrients by nuking it

  16. Once again, Dr. Greger and the nutritionfacts.org site FTW! I was so happy to see this pop up when I googled “best way to cook sweet potatoes!!

  17. What about pressure cooked sweet potatoes and the GI cooking them that way? I would assume the GI would be lower than any other way of cooking them, yes or no?

  18. When it comes to vegetables pretty much every cooking method has been looked down on for some reason. I’d never ever fry foods but baking, steaming, and boiling are common ways of cooking vegetables.

    Some people oppose baking sweet potatoes, while some says it is the healthiest way. Some say the same thing for steaming them or boiling them. People have looked down on these three cooking methods for different reasons.

    I think the best way to eat sweet potatoes is to eat them they way you enjoy them and like them. As with any vegetable make sure you aren’t overheating them and overcooking them. For baking I recommend a lower temperature for cooking them.

  19. Wondering if Sweet Potatoes microwave as well as they boil? You may have covered it and I glossed over it. If I did, just tell me to read it again! Thanks, L.

  20. Cooking food is simply using heat to induce a chemical reaction among the chemical constituents of the food. The best known of these reactions is the Maillard reaction, responsible for “browning” of food although many more reaction occurs depending on the actual components of the chemically complex foodstuff in question. Such is the world of organic chemistry, far beyond the scope of a text.

    We can manipulate the conditions which start and support these reaction by cooking method, boiling, frying, roasting, etc., but in essence, we are controlling temperature (very different from heat) and time. Pressure is another variable if you’re into pressure cookers, but basically pressure determines temperature if you’re cooking with boiling water as the temperature of the boil varies with atmospheric pressure and altitude.

    To simplify, the boiling method uses water to precicely regulate temperature at 212° F (100° C) at standard atmospheric conditions (water boils at lower temperature at night elevations which have lower atmospheric pressure). So, using boiling, the primary variable left is time; how long do we boil the food? The longer the boil, the softer (more broken cell walls/more chemically reacted) the resulting food. Boil our sweet potatoes long enough and we will have soup instead.

    BUT, we now have a method of precicely controlling cooking temperature of water at lower temperatures than boiling; sous vide cooking. With sous vide, we can cook at much lower temperatures, PERHAPS limiting/controlling chemical reactions that occurs more rapidly at higher temperatures, thus preserving the nutrients in the foods.

    I personally have no experience to share, but I’m throwing this out to stimulate others to share their experiences and the science involved.

Leave a Reply

Your email address will not be published. Required fields are marked *

Pin It on Pinterest

Share This