Grains and Toxins

Grains and Toxins | The Paleo Diet

Hello sir,

I am a big fan of Dr. Mercola and recently I saw your video, and article excerpts from Dr. Mercola in which you state:
“Grains are the seeds of a plant. They’re its reproductive material, and plants don’t make their reproductive material to give away for free to other animals. If they did they’d become extinct, and so the evolutionary strategy that many plants, particularly cereal grains have taken to prevent predation is to evolve toxic compounds so that the predator of the seeds can’t eat them, so that they can put their seeds in the soil where they’re meant to be to grow a new plant and not in the gut of an animal to feed it.”

My brother was very dubious about this claim and made this comment:

“The quote about plants not wanting animals to eat them is false for many, many species that rely on animals to eat them, travel some distance and then defecate them as a seed spreading strategy (a fundamental fact in plant biology). Also, is internally inconsistent I think because there are likely many plants and fruits that use this strategy, where we eat the fruit (seed and all in many cases) where the author would declare them very healthy. ”

Frankly, he stumped me.  Any comments?



Dr. Cordain’s Response:

Hi John,

Your brother is absolutely correct with the single point he brings up.  However, had  he, you or Dr. Mercola read my recent book carefully, The Paleo Answer (John Wiley & Sons) or a number of my peer review scientific papers, you would have realized that the quote below, was only a single paragraph of a much larger point I had made.  Seeds (cereal grains, legumes, etc) indeed are the reproductive materials of plants, and if they are consumed in their entirety by a predator, the plant would rapidly become extinct.   As I have pointed out in my most recent book and previous scientific papers, plants have evolved three major strategies to resist predation, so that their reproductive material (their seeds) can survive to produce the next generation.  These three mechanisms are: 1) toxic compounds to discourage predation, 2) structural barriers to predation such as spikes, thorns as found in cactus or hard impervious shells such as found in coconuts and brazil nuts, and 3) the mechanism your brother mentioned:  a sweet, attractive outer layer (fruit) that encourages predation, combined  with hard, small seeds within the fruit that are impervious to the digestive tract of the predator and pass through the digestive tract into the feces which spread the seed from its original site along with a nice dose of fertilizer.
Cereal grains (wheat, rye, barley, oats, corn, rice, sorghum etc)  and legumes (beans, lentils, peas, garbanzo beans, peanuts etc.) most typically have evolved toxic compounds to prevent predation.  These antinutritional compounds include lectins, saponins, protease inhibitors, phytate, thaumatin like proteins, alkylresorcinols, and others whose effects range from lethal toxicity to mildly benign depending upon the antinutrient and the species of predator.  A wealth of scientific literature exists to support these concepts.  I have devoted  at least three chapters of my new book, The Paleo Answer,  to antinutritional compounds in common foods and their adverse health effects.  I have provided hundreds of scientific references in the book documenting these effects that your brother may wish to examine specifically.  Further if you go to my website (, you can download this paper (Cordain L, Toohey L, Smith MJ, Hickey MS.  Modulation of immune function by dietary lectins in rheumatoid arthritis. British Journal of Nutrition, 2000, 83:207-217. ) which outlines some, but not all of the underlying mechanisms.

Best wishes,

Loren Cordain, Ph.D., Professor Emeritus

“3” Comments

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  4. Interestingly, and since I study fish, I have a specific example of how Dr Cordain is correct. Herbivorous fish will often avoid plants that contain these chemical defenses preferring to eat the plants that lack these.

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