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Toxins in Cooked Potatoes?

Natural glycoalkaloid toxins concentrate in the skins of potatoes.

December 29, 2009 |
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Transcript

Any other natural toxins to consider? Well, potatoes produce these natural insecticide compounds called glycoalkaloids to keep potato beetles from nibbling on them—they’re not stupid. So bad for beetles, but what about us?
Well, a number of dietary risk assessments have been published lately, and although these glycoalkaloids are thought to be the most highly consumed natural toxin in North America, people have been growing potatoes for 7000 years, currently the 4th largest food crop in the world.
Major review just published, what do you think? Now this is for a baked potato, not fried, no butter, no cheese, no sour cream—no salt. Just a plain baked potato. Bad, neither, or good?
True safety, or false sense of security? Asking the question of “vital importance.” Are potato glycoalkaloids dangerous to humans? This discussion suggests they are indeed toxic and this problem should no longer be ignored. OK, then.

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.

To help out on the site please email volunteer@nutritionfacts.org

Dr. Michael Greger

Doctor's Note

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

  • http://nutritionfacts.org/members/mgreger/ 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    New (as-yet-unpublished) study evidently suggests that the consumption of purple potatoes may significantly improve blood pressure of overweight and obese individuals.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?

  • http://nutritionfacts.org/members/KarenHyde/ Karen Hyde

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

  • http://nutritionfacts.org/members/BenjaminStone/ 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.

  • http://nutritionfacts.org/members/MaryZdrojewski/ 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).

  • http://nutritionfacts.org/members/lonestarnot/ lonestarnot

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

    • http://nutritionfacts.org/members/mgreger/ 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.

  • http://nutritionfacts.org/members/leif-varmark/ 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!

  • http://nutritionfacts.org/members/dave23/ dave23

    Do you recommend not eating plain potatoes ever?

  • http://nutrientuniverse.blogspot.co.uk/ 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,

      http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2770/2

      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.

      https://www.facebook.com/notes/jeff-novick-ms-rd/potatoes-diabetes-dietary-trends-truths-about-taters/434650191818

      • http://www.DonForresterMD.com/ 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.

  • 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.

    Source

    Healthy Science Communications, LLC.

    Abstract

    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.