The Danger of Plant Foods

Recently, an 88-year-old Chinese woman was brought to the emergency department at New York University’s Tisch Hospital by her family. She had been lethargic and unable to walk or swallow for 3 days. [1]

She had been eating 2 to 3 pounds of raw bok choy daily for several months in the hope that it would help control her diabetes, and the bok choy had poisoned her thyroid. In addition to coma, her symptoms included low body temperature (36 C), a shrunken thyroid, dry skin and coarse hair.  Her life was saved by high doses of intravenous thyroid hormone, but she still needed four weeks in the hospital before she could be moved to a nursing facility.

Remarkably, but not surprisingly in light of how little publicity is given to the dangers of plant toxins, her family wanted to keep feeding her raw bok choy in the hospital! [2]

This episode is a timely reminder that most of the toxins in our bodies come from the plant foods we eat.  Plant toxins can be quite dangerous. 

For good health, exposure to plant toxins should be minimized by:

  1. Cooking most plant foods other than fruits and berries, which are relatively non-toxic.  The heat of cooking destroys many toxins, and renders many others more digestible.
  2. Diversifying plant food sources.  Don’t eat too much of any one plant; rather try to eat modest amounts from many different species.  Live by the toxicologists’ rule, first formulated by Paracelsus:  “The dose makes the poison.”  If you keep the dose of any one toxin low, it will not poison you.
  3. Eliminating the most toxic foods.  These are grains; legumes; oils from grains, legumes, and seed crops; and fructose sugars.

The Paleo principle – it’s healthiest to eat like a caveman – is a good guide to low-toxicity eating.  Paleolithic peoples gathered a wide variety of plants – hundreds of species – and did not eat the Neolithic agricultural crops. Agriculture needs plants that produce an abundance of calorie-rich seeds, but these are precisely the plants that load their seeds with high levels of toxins to discourage herbivores.

Eat like a caveman, and stay out of the hospital!

[1] Chu M, Seltzer TF. Myxedema coma induced by ingestion of raw bok choy. N Engl J Med. 2010 May 20;362(20):1945-6.


Leave a comment ?


  1. Yes, yes! The way to go is paleo! And even if you cook it, you should stick to foods that are edible raw.

  2. Perfect Health Diet » Plant Pesticides - pingback on June 20, 2010 at 5:12 pm
  3. I think that this is crazy. 3 pounds of raw bok choy daily for several months is not to say that plant foods is toxic. What do you think it would happen if one would eat 3 pounds a day of healthy fish or meat? Or healthy fats?

  4. if people drink 7 liters of water in a couple of hours they will die. But water is not toxic. Of course it is in abysmal quantity yes…

  5. Hi tiago,

    Bok choy is rich in goitrogens. Water is not. I agree, 3 pounds of anything a day is a bad diet, but 3 pounds of potatoes a day would not be toxic, see Chris Voigt’s experience. He ate 6 pounds of potatoes a day for 60 days and did just fine (, although it was a lipid-deficient diet and he would have run into trouble long term.

  6. From “Potato: a history of the propitious esculent” by John Reader, when discussing potato consumption in the late 18th and early 19th centuries:

    ‘More recently, the historian Kenneth H. Connell puts the average consumption for an adult Irishman at around 10 pounds of potatoes a day.’ Also, it was customary to have a cup of milk with each meal.

  7. Ooh my next post is going to be on a link between parkinsons and genes associated with poor mitochondrial efficiency. Can’t wait to see your zero carb info, because I still have some more questions about VLC and ketosis and I’m certain your take will be illuminating. As you know, ketosis would increase mitochondrial efficiency in the brain…

  8. I wonder if eating hundreds of plant species ends up limiting your gut flora diversity to only a few generalist species.

    See this blog post for what I mean (under “Generalizations about Gut Bacteria”):

    Then the question remains, which is better a better gut flora, a whole lot of different species or a few generalist species?

  9. Anyone read this or have any thoughts? I received it today and was wondering if anyone wanted to weigh it on it:

  10. Hi Paul,

    What do you think of eating ~2 pounds raw sweet peppers per week (not per day!), plus ~2 pounds of raw guavas?

    On the positive side, that would average out to ~500 mg of vitamin C per day by itself (~200 mg from the sweet peppers, plus ~300 mg from the guavas).

    On the negative side, I assume the risk from plant toxins would be higher than if you ate an equivalent amount of bananas for your sweet plants instead… is this a concern?


    • I think it should be fine. Diversity of plant foods is good, but if you insist on getting C from food, then this would be a good way to do it.

      Best, Paul

      • Hi Paul,

        OK, thanks!

        I had been trying to get all nutrients (except D and K2) from food as an experiment, and noticed as a result that I needed substantially fewer calories to feel satisfied, which I assumed was a good sign.

        But I made multiple changes at once — more extracellular matrix for glycine; more leafy greens for B1; more mushrooms, sweet potatoes, endive, avocado, celery, and cucumber for B5; more sweet peppers and guavas for C. So something else may be responsible, and maybe the optimal solution involves vitamin C supplementation to maximize diversity of plant foods.


        • Hi Eric,

          Great experiment with the food only approach. The reduced appetite definitely indicates better nutrition (per the theory of our chapter 17). But, I’d say it’s not clear that (a) you’ve necessarily reached the optimum intake of C or (b) that you might not be even better nourished with C supplementation and more diverse plants.

          At this level of optimization it is better treated as an empirical question, so I guess I’d propose a few experiments: (1) Keep everything the same as you are doing now, but add extra C in tablet form. Better or worse? (2) At the higher C intake (presuming removing C as a factor because you’ll be near the optimum and differential intake from food will have no effect), try replacing half the guavas with other fruits and either cooking the sweet peppers or replacing some with other cooked vegetables. Cooking and diversification should both reduce any potential toxicity risk.

          Best, Paul

          • Hi Paul,

            Thanks again!

            I’ll definitely try the experiments you suggest! It’ll probably take me a while to gather accurate data (especially if I test various B vitamins too) — I’ll post again when I have results (probably in several months).


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