Toxins in Sweet Potatoes?

Toxins in Sweet Potatoes?
3.89 (77.86%) 28 votes

Sweet potatoes are one of the healthiest known vegetables.


What about sweet potatoes? Bad, eh, or good? They’re not good; they’re great! Ranked as one of the top ten healthiest foods on the planet by Mayo Clinic.

So, sweet potatoes good; white potatoes bad. If you insist on continuing to eat white potatoes, peel them, as that removes about three-quarters of the toxins.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by veganmontreal.

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What about sweet potatoes? Bad, eh, or good? They’re not good; they’re great! Ranked as one of the top ten healthiest foods on the planet by Mayo Clinic.

So, sweet potatoes good; white potatoes bad. If you insist on continuing to eat white potatoes, peel them, as that removes about three-quarters of the toxins.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by veganmontreal.

Please consider volunteering to help out on the site.

Doctor's Note

Check out these videos to learn more about sweet potatoes:
Anti-Cancer Potential of Sweet Potato Proteins
The Best Way to Cook Sweet Potatoes

And check out my other “HHH” videos (Harmful, Harmless, or Helpful?) – listed below the post.

For more context, please check out my associated blog post: Soymilk: shake it up!

If you haven’t yet, you can subscribe to my videos for free by clicking here.

33 responses to “Toxins in Sweet Potatoes?

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    1. Hi Dave,
      You’re better off not eating the skins.  Although they may contain nutrients, potato skins are still not worth eating due to their toxic properties.  Peel the skin, and try to occasionally substitute white potatoes with sweet potatoes to boost your nutrient intake.
      I hope this helps!

    1. I wonder the same thing. There are many different versions of sweet potatoes such as the purple sweet potato, the Japanese sweet potato, Okinawan sweet potato, and as you mentioned white sweet potatoes along with a few others. I’m not so much of a fan of the orange/reddish ones either.

      Also wondering if other sweet potato varieties are just as good.

  1. Could you clarify what you mean by white potatoes? Would this include russets, yukon golds, etc.?

    Thanks a lot! I love your website :)

  2. Now that we know we can eat nuts ( and nut butters ( without fear of weight gain we can use them to flavour this surprisingly amazing stew which just so happens to contain one of the healthiest vegetables

    Peanut/Almond Butter Barley Stew

    -1 ½ cups barley*
    -3 cups water/homemade vegetable broth
    -1 red onion, chopped (
    -2 cloves garlic, minced (
    -½ inch piece of fresh gingerroot, minced
    -4 carrots, diced
    -1 large sweet potato, cubed
    -jar strained tomatoes
    -1 tsp cumin
    -pinch cayenne pepper
    -2 tbsp unsalted peanut or almond butter
    -chopped peanuts/almonds for garnish
    -sea salt and black pepper to taste

    Place all ingredients except peanut butter, peanuts, and salt into a large soup pot. Cook for 40 minutes until barley almost cooked. Add peanut butter and cook until it has melted and heated. Season to taste with sea salt and black pepper. Serve garnished with peanuts.

    *If sensitive to gluten substitute with buckwheat

    ~Complements of lovestobevegan

  3. What about yams? I see sweet potatoes and yams used interchangeably in the store often. Following the rule of more colorful usually = better, I’d pick a garnet yam over the less colorful sweet potato. But which is actually better?

    We eat whole food/plant based in our family, and have a young child, so I’m conscious of what we eat. But the sweet potato/yam question is still unclear to me. Thanks!

    1. I would not worry about this, because both of these foods are quite healthy. Usually it is the case that the more colorful foods have more antioxidants but these foods are both very healthy so its not much concern.

  4. I always like to check sources. But in this case, there’s an apparent contradiction. Salmon is also in their top ten healthiest foods list, so by the exact same logic, salmon is also great for you! But I thought you were against all fish consumption (mercury, PCB’s, heterocyclic amines, etc.)?

  5. Dear Dr. Greger,

    I was wondering about the different types of sweet potato. In my local supermarket they sometimes have the ones with orange flesh but more often the red ones with white flesh, though they’re sold under the same name.

    Both ok, or just the orange ones?

    Thank you,

    Coen (from the netherlands)

    1. All foods contain antinutrients. Eggs and Dairy inhibit Iron, so does soy protein and phytic acid. Calcium also inhibits Iron absorption, as well as Zinc. However, adequate intake of the recommended daily value is likely to be enough to counter any anti-nutritious effects of plant foods. If you’re really worried, the recommended intake for men is 16 mg a day – accounting for the absorption rate of non-heme iron – so just eat a bit more than that. The greatest concern with potatoes is that the skin is rich in polyphenols. Most of these polyphenols are incredibly good for human health, but some of them have the added side-effect of inhibiting Iron absorption by as much as 99%. Catechins in tea and gallic acid in berries are the most potent, and are present in sweet and white potatoes – and yams. This study showed a neutral effect from the polyphenols in sweet potato because they are also rich in Vitamin C which counteracted most of the polyphenols.
      However, there is no reason to avoid Sweet Potatoes or Yams – or even White Potatoes, Dr Greger is just overreacting – just eat them with low-polyphenol-high-vitamin C foods that will help untangle the Iron from the grasp of the sweet potato polyphenols.
      Low Polyphenol foods would include broccoli, cruciferous vegetables and peeled fruits.

      Good news, however, is that the current perception of polyphenols as inhibitory to iron absorption is being eroded by the revelation that very few of these studies obey the necessary criteria to be considered valid. This analysis showed that polyphenol-rich beans and grains may actually have better Iron absorption than their lighter-coloured high-phytate equivalents.

  6. I had sweet potato lady week and since then I am having some symptoms related to brain fog, confusion, irritability. I am also feeling more calmer but overall feeling irritated and hyper. Please advise.

  7. Please tell me about Murasaki Sweet Potatoes, they have purple skin and white flesh – are these good for you? If you juice them for G-tube feeding, should the skin be left on? What variety of sweet potato are the purple ones the Dr. recommends?

  8. So apparently the skin on sweet potatoes is fine/safer? I don’t eat regular potatoes all that much (not a fan). Just wondering though about the skin on a sweet potato safe or not?

    1. I did a thorough search in Medline looking for studies specifically zeroing in on the safety of sweet potato skins and found that most studies focused on white potatoes. It appears the type of pesticides used on sweet v white potatoes and while washing can be effective in eliminating the pesticides fairly well Consider this:
      Effect of handling and processing on pesticide residues in food- a review
      Washing with tap water or aqueous solutions of acetic acid and/or NaCl, and blanching or frying of potatoes also removed most residues.
      I would suggest that washing might be more effective with sweet potatoes since the often do not have the additional “knobs’ that white pototoes have making thorough washing less effective. I was able to track down this study which may make you feel better about eating sweet potato skins than white: You can compare the pesticides found with analysis of both sweet and white potatoes with 35 pesticides identified in the white, only 19 in the sweet and of those 6 known carcinogenic pesticides identified for white, only 3, in much less concentration in sweet.
      Carcinogenic of course sounds alarming, but I found many research studies validating the benefit of the fiber found in sweet potato skins which also should be considered. I can’t give you a yes or no answer, but these studies may help you determine whether to pell or sweet potatoes or not.

  9. I am so confused about sweet potatoes. Sweet potatoes are reported as one of the healthiest of foods. In stores the ones I see have a white skin and white flesh or purple skin and purple flesh. Yet in recipes they show yams. In this article from Mayo they are talking about orange which is a yam. However yams are reported to not be as healthy. I prefer organic and I’m finding it hard to find them. Is it from this confusion that stores think yams are just as healthy as sweet potatoes? I’m a very detailed person and I’ve always worked to have sweet potatoes and yet the whole world seems confused about this. Which is the healthiest?

  10. I love your site and have read both how not to die-I call it my bible ;) (3 times) and how not to diet-my encyclopedia.

    I’ve been fighting with sugar addiction for a few months now since I switched to a whole plant based diet. If I allow myself a cheat and try to have one cookie or one chocolate bar it turns into a full out binge leaving me feeling terrible. I never had these issues before when I was consuming sugar regularly. I’m currently on day 34 with no added sugars (except a little in one of my favourite oil free salad dressings but I don’t use it daily).

    I’ve found I absolutely love sweet potatoes (especially the Japanese anno imo or orange fleshed yam in English). This potato has very high levels of sugar so I’m worried that it is counter productive to my goal of getting over my sugar cravings/addiction. I know there are different types of sugars and that the natural sugar in fruits and vegetables are good for us but I’m concerned about this type of potato specifically as it has such high levels of sugar. I crave them regularly and eat them on a daily basis. I’m wondering if I should be trying to avoid them or if I have the green light to go sweet potato crazy! Currently I’m eating 2 or 3 large baked anno imos daily, nothing added!

    Any advice or information would be greatly appreciated! Also any extra tips for kicking my sugar addiction would also be amazing! Lastly is balsamic vinegrette ok? I can eat an endless supply of greens if I use that as my dressing with some berries mixed in!

    Thanks again!


  11. Christina, you’ve stumbled on the solution, not the problem. You are addicted to sugar since this is the only nutrient your brain has evolved to use for fuel. Ketone bodies are emergency fuel only and even with ketone bodies, your brain still requires some sugar. Sugar is also one of the few, if not the only, innate craving that humans have. All/most other taste desires are learned. Sugar is good/great for you. The form/package that it comes in is where the problem arises. For 20 million years our physiology has become accustomed to squeezing out the difficult to extract sugars from low calorie density unprocessed plant foods and the plant cellulose that the sugar is bound to. Our physiology is not accustomed to accommodate the massive influx of sugar that comes from refined and high calorie density foods, like cookies. When we eat a cookie (or three dozen) we are flooded with massive amounts of sugar (and refined fat) that we are not accustomed to. Its like our bodies are trying to take a sip of water from a fire hydrant on full power. Our physiology shunts this massive influx of sugar to our liver where it’s turned into fat while spiking our insulin levels to the extreme. All of this is not good. Contrast this with optimal sugar intake such as eating a sweet potato or two, or a big pile of fruit. In these cases, our physiology is functioning perfectly to utilize this influx of sugar, because its in low to moderate amounts and bound to the plant cellulose which moderates the rate of absorption. The outcome of all this is that if you constantly eat all day what you were designed to eat (sweet potatoes and fruit), you won’t crave cookies. As a matter of fact, in time, the cookies won’t taste very good and you won’t feel well at all when you eat them (like what you experience now). Over time, you’ll avoid cookies since you’ll be tired of getting sick every time you eat them. By the way, the cookies have very high levels of sugar (and fat) at 100+ calories per ounce. The sweet potatoes are only about 35 calories per ounce which might be on the high side for plants, but this is on the very low end for typical processed/refined food….and yes, balsamic vinegar is ok, but it does usually have sugar in it, so by the tablespoon is ok, not by the cup.

    1. Thank you so much for the response! I’m glad to hear that I don’t have to give up my sweet potatoes! You mentioned 1 or 2 is fine… but I’m eating about 4-5 large sweet potatoes a day. And lots of berries. Do you see that as being a problem? The sweet potatoes are my main source of starch beside 1/4 cup oat groats I eat for breakfast.

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