Doctor's Note

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  • Michael Greger M.D.

    New (as-yet-unpublished) study evidently suggests that the consumption of purple potatoes may significantly improve blood pressure of overweight and obese individuals. If you choose to continue to eat potatoes, choose the varieties with colored flesh (though I suspect that sweet potatoes still remain healthier overall).

    • LynnCS

      I prefer the light sweet potatoes and almost don’t like the dark ones at all. I would love to hear that my choice is a good one and fits in your statement of remaining healthier overall. Hmm?

    • Waste of Time

      “This discussion SUGGESTS they are indeed toxic” and further studies will say they are not after all.

  • Karen Hyde

    Michael, Could you provide a list of the food you consider to be safe and nutritionally beneficial please?
    Thank you.
    Karen :)

  • Benjamin Stone

    I believe for a variety of reasons (incredible nutritional profile, lower glycemic index, edible raw or cooked) that sweet potatoes – a staple of many long-lived cultures – should always be consumed over potatoes.

  • Mary Zdrojewski

    Does this include all potatoes that are not sweet potatoes – even like Yukon golds and red skins and purple potatoes? (I saw your post about purple and blood pressure, and I don’t need to lower my blood pressure).

  • lonestarnot

    Yes, what’s the verdict on gold, red & purple potatoes?

    • Michael Greger M.D.

      The healthiest potatoes are probably sweet potatoes (see my video about sweet potatoes), but if you are going to eat plain potatoes, the varieties with colored flesh (not just skin) do appear healthier. A new study published this month found that the consumption of 6-8 microwaved purple potatoes a day (they’re pretty small) resulted in a boost in antioxidant capacity of the blood (whereas the plain potato starch control acted as a pro-oxidant) and a drop in blood pressure in overweight individuals. “Thus,” they concluded, “purple potatoes are an effective hypotensive agent and lower the risk of heart disease and stroke in hypertensive subjects without weight gain.” Last year a study found that purple potatoes appeared to suppress both early and late stage human colon cancer cells in vitro, but only if they were fresh. After being in storage a few months their anti-cancer properties diminished. And finally, another study published last year (and this one available full-text), found a trend towards lower inflammation in men eating purple potatoes than white, concluding “Pigmented potato consumption reduced inflammation and DNA damage in healthy adult males. This offers consumers an improved nutritional choice in potato consumption.” Purple sweet potatoes may offer the best of both worlds, as suggested in an in vitro study last year on human fat cells that suggested anti-obesity, anti-oxidant, and anti-inflammatory benefits.

  • Leif Varmark

    »The healthiest potatoes are probably sweet potatoes (see my video about sweet potatoes), but if you are going to eat plain potatoes, the varieties with colored flesh (not just skin) do appear healthier«

    Oh yes, but your video tells me that the »normal« potatoe, I – and untold millions – eat, is harmful. I can hardly believe that!

  • dave23

    Do you recommend not eating plain potatoes ever?

  • JamesKB

    Do you think the levels would be insignificant in potatoes that were entirely or almost entirely free of green. Some suggest we just need to be more careful with storing them (farmers that is). I would agree that even slightly green potatoes you should say no to though and there are better choices of course.

  • Tobias Brown

    I follow your reports closely and this has to be one of your most questionable positions. White potatoes harmful. You should know that in John McDougall’s latest book “The Starch Solution” he cites white and sweet potatoes as the most nearly perfect foods, very early in the book. He claims these two foods each alone could sustain human life (add b12) fairly well. So, next to nixing avocados 86ing the white potatoes leaves me feeling quite doubtful. And the problem with raising such doubt on a few items with viewers like me is that it forces me to reduce my level of confidence slightly in all of your statements. I suspect another example is your positive view on cocoa. This food can be quite dangerous to some animals (dogs, for example). And it’s clearly “the rage” in health food stores now. A fad? So, maybe it’s time to cut cocoa down a few notches by comparing it head-to-head with carob. Please? Anyway. I wish you would have another category for evaluating foods: The jury is still out ( or uncertain). Placing a harmful rating on some foods is a very difficult proposition!

    • Toxins

      I am also in disagreement with Dr. Greger’s view on white potatoes, while I still do not eat avacados for more complex reasons. Potatoes are quite nutrient dense and satiating,

      I think the main issue that we find in studies are that potatoes are lumped together with french fries or potato chips which are the least bit healthful.

      Jeff Novick really cuts into the potato concern quite well here.

      • Don Forrester MD

        I appreciated your post especially the link to Jeff Novick’s facebook notes which is excellent. I have found the nutritiondata website useful as well for looking up details. I was surprised to see the amount of Vitamin C and Folate in 300 grams of a white potato. I was surprised to see that it is listed as an inflammatory food as it is primarily starch (i.e glucose) and very little fructose. I wasn’t surprised that I couldn’t ferret out the details of the equations used to calculate the number… sorry my undergraduate training as a chemical engineer drives me to the equation before I put any credence in a number whether that is the Inflammatory Factor on nutritiondata or Nutrient Density in Whole Foods. If you look at the ratio of Omega 6/3 it is about 4/1 which is acceptable. Toxins… thanks again for the post.

  • Tobias Brown

    Does this glycoalkaloid toxin problem apply to the whole potato or to j
    ust the skin?

    • LynnCS

      I have the same question. When I boil potatoes, the chemicals must be in the water and therefore effect the meat of the potato.

    • Joe Caner

      According to ( “In normal tubers, potato glycoalkaloids appear to be concentrated in a small 1.5 mm layer immediately under the skin, therefore, with normal tubers, peeling will remove between 60% – 95% of the glycoalkaloids present.”
      But since their is a higher concentration of nutrients in the skin, one is in effect throwing the metaphorical baby out with the bath water nutritionally speaking. The article goes on to say that potatoes that are high in glycoalkaloid toxin, the green and sprouting ones, have a greater percentage of the toxin in the flesh, and that the glycoalkaloids are heat stable until the very high cooking temperatures found in deep frying which impart their own set of problems.

  • Nunya Biznez

    Hmm… I dunno. Peruvians seemed to use it as a staple (I think it was Peruvians).

  • LynnCS

    So, it’s pretty easy for me to peel my cooked Yukon Golds, the Russets are a little harder and I can’t see peeling a baked pot. To think that I used to eat the skins and not the insides. Anyway, are baked even good for us at all? I’m just about ready to get my new stove put in and dying to bake up a big batch of baked potatoes. Hmmm. Should I give up the dream?

  • Ruth Houston Barrett

    Ann Med. 2013 Nov;45(7):467-73. doi: 10.3109/07853890.2013.813633. Epub 2013 Jul 15.

    The role of potatoes and potato components in cardiometabolic health: A review.

    McGill CR, Kurilich AC, Davignon J.


    Healthy Science Communications, LLC.


    Abstract Potatoes (Solanum tuberosum) are an important food crop worldwide and contribute key nutrients to the diet, including vitamin C, potassium, and dietary fiber. Potatoes and potato components have been shown to have favorable impacts on several measures of cardiometabolic health in animals and humans, including lowering blood pressure, improving lipid profiles, and decreasing markers of inflammation. A range of glycemic index (GI) values have been reported for potatoes, and data are sparse regarding the impact of potato consumption on the postprandial glycemic response, especially when potatoes are consumed with other foods. There is a lack of clinical trial data regarding the impact of potatoes on weight management. A small number of human cohort studies have reported beneficial associations between potato consumption as part of a healthy lifestyle and cardiometabolic health. Another small number of human population studies have included potatoes as part of a dietary pattern with other calorie-dense foods and have not reported cardiometabolic benefits. The epidemiological literature should be interpreted with caution due to lack of consistency in both defining dietary patterns that include potatoes and in control for potential confounding variables. Controlled clinical trials are needed to define the impact of potatoes on cardiometabolic health.

  • Tobias Brown

    This video does not appear under potatoes when you search the index bar on the left side of the site.

  • Tobias Brown

    This has to be the one report on this site that is most likely to be WRONG. Really wish we could get some solid information on eating white potatoes. So many resources say that they are a great food. And Dr Greger says they aren’t based on this one study? or are there many studies supporting his ADVICE here?

    • Gayle Delaney PhD

      Are the delicious skins of the variously colored sweet potatoes toxic, or super healthy?

      • Tobias Brown

        Dr Greger recommends sweet potatoes — including the skins. He also recommends varied color ones… especially darker purple ones.

  • Vegg-E

    I have a better chance of finding diamonds in my backyard than finding purple potatoes in ANY store around me. They are the one food nobody carries!? Not whole foods… not mothers market… no place in Southern California carries purples… I’d make the switch if I could find them as I love red potatoes and eat them every day, practically every meal as suggested by our good friend Dr. John McDougall. If I ever go on one of those health cruises. I’m going to strait up ask both Dr.’s to stand up and debate over our beloved white or red potato. (I hope McDougall wins). =)

  • HereHere

    I’m not sure about the conclusions on the harms of the white potatoe. When I went to the sources cited, one study was a model, and the other was based on testing on hamsters. Perhaps the evidence is pointing away from the healthiness of white potatoes, but these conclusions seem to be based on weak data. I have to admit, I didn’t read the whole articles, just access to the free text (in this case, Abstracts only).

  • Charma1ne

    Perhaps the study points toward toxicity because potatoes belong to the notorious Deadly Nightshade family. Many people react to foods belonging in this family group. There is always good information to had on this site that is always backed up by research and peer reviews. Thank you Dr. Greger.

  • Bruce Cropley

    I have been told that the glycoalkaloids in potatoes are due to solanine, in green parts of the potato, and they can be eaten safely as long as there are they are kept in the dark, there are no deep green parts, and any green on the skin is discarded. What do you think?

  • Sara

    Is this proven? I don’t quite understand how potatoes can be harmful?

  • charlespeden

    Potatoes contain glycoalkaloids which are toxic to humans but have a generally accepted safe level (200 mg/kg). Glycoalkaloids also are not cleared from the body in 24 hrs so they may accumulate if eaten regularly. Glycoalkaloid safe levels are considered “safe” because they don’t usually cause acute problems at that level (although I did read one anecdote of someone throwing up at the 200 mg/kg quantity). However, the potential for long term problems were not tested, so long term safety is unknown. All of this can be found in Pub Med.
    If they seem safe because a lot of people are eating them, you might want to rethink that. A lot of people are eating cheeseburgers, too. I think potatoes, blue or otherwise, deserve to be in the suspect food category due to Glycoalkaloids. If they are eaten at all, it should be rarely or occasionally.

  • Wilma Laura Wiggins

    Send to:

    J Agric Food Chem. 2000 Jun;48(6):2472-5.
    liquid chromatographic determination of the glycoalkaloids
    alpha-solanine and alpha-chaconine in 12 commercial varieties of Mexican
    Sotelo A1, Serrano B.
    Author information
    glycoalkaloid content in 12 commercial varieties of Mexican potatoes
    was measured by HPLC in both the peel and the flesh of the potato. The
    principal glycoalkaloids alpha-solanine and alpha-chaconine were present
    in higher concentration in the peel than in the flesh of all varieties.
    The main alkaloid in the peel of the potatoes was alpha-chaconine and
    comprised about 65-71% of the total glycoalkaloids. The high
    concentration of alpha-chaconine in peel, which is more toxic than
    alpha-solanine, gives more protection to the tuber against predators.
    The total alkaloids in the peel of Alpha, Juanita, Michoacan, Norteña,
    Rosita, and Tollocan varieties were higher than the limit recommended
    for food safety. However, the peel represents less than 10% of the total
    tuber in most of the varieties. The total alkaloids contained in the
    peel of Atzimba, Lopez, Marciana, Montsama, Murca, and Puebla was lower
    than the limits recommended for food safety. The glycoalkaloid content
    in the boiled peeled potatoes was less than 9 mg/100 g but in Alpha,
    Montsama, and Puebla varieties, both glycoalkaloids were absent.
    According to the results, the consumption of the 12 commercial varieties
    of Mexican potatoes does not represent any danger to human health.

  • kate

    we just bought potatoes and they have red in them if they are cooked or raw are they ok to eat?

  • Miroslav Kovar

    I have only found studies exploring the short term effects, like this one: It seems the alkaloids have gastro-intestinal and systemic effects. But what are the long term effects? Obviously, anyone can notice the immediate effects of poisoning, so the main worry is about the long term effects. Are there any studies exploring those? Or are there any expected effects? Thanks!