In this post, I want to point to two sources that have helped me understand and embrace the idea that vegetables not only are not necessary for good health, but they may actually do harm in many people.
The first is a curious small study from 2002 in the British Journal of Nutrition. The point of the study was to see if the anti-oxidants in green tea have a positive effect on oxidative markers of stress. In order to make sure the effect was coming from the tea, they removed all fruits and vegetables (except potatoes and carrots) from the subjects' diets. The researchers didn't find any long-term effects from the green tea extract, but they did notice something interesting. The removal of flavonoid containing elements of the diet did improve those markers. A "decrease in protein oxidation, in 8-oxo-dG excretion and in the increased resistance of plasma lipoproteins to oxidation in the present study points to a more general relief of oxidative stress after depletion of flavonoid- and ascorbate- rich fruits and vegetables from the diet, contrary to common beliefs." In other words, it appeared in this study that not eating fruits and vegetables was better for the participants than eating them. If nothing else, this must give one pause.
The second I came upon just this week. At the 2nd Annual Ancestral Health Symposium 2012 (AHS12), Georgia Ede, M.D. gave her presentation titled "Little Shop of Horrors? The Risks and Benefits of Eating Plants". In it and on her website, she points out that there are no studies that she could find (and the above is the only one I know of) that actually compares diets with and without vegetables. The studies that she did find that showed positive benefits to eating vegetables are all flawed in some way such that it can not be determined which aspect of the intervention gave a positive benefit. For example they had people eat more vegetables and less refined sugar, or eat more vegetables and exercise more. Moreover, the only studies she found that did not have these confounders, had negative results, that is, they did not show the benefits the researchers were expecting. Of course, this is only absence of evidence, but with the extensive promotion of vegetables that we are exposed to so vigorously, one would hope to see something more concrete behind it.
Dr. Ede notes that there have been groups in the past that survived fine without vegetables. She makes cogent arguments against the assertions that fiber is beneficial, and that vegetarians are healthier than non-vegetarians. She shows that micronutrients are more abundant and/or more bioavailable in animal foods than in plants. Yet the most important insight she provides from my perspective is that there are many compounds in plants that function as protection for the plant, to prevent it being eaten. Even though many people can tolerate them at low levels, in high doses (or low doses for sensitive individuals) they are at best double edged swords, and at worst harmful. This is true even of compounds that have been touted as health-promoting, such as anti-oxidants.
She promises to write about many classes of toxins, and the first article has already been written. It describes the problems with brassicas (a.k.a. cruciferous vegetables). When I was on a simply low-carb diet, instead of a "zero-carb" diet (that's a bit of a misnomer, since there are trace carbs in meat, and I sometimes eat liver or cream, which have a bit more) I ate a lot of those, because they are very low in carbohydrates. As she claims seems to be the pattern, the ingredients in brassicas that are advertised as fighting disease, also cause problems, actually poisoning mitochondria, generating ROS's, and more. I recommend reading her post, and the rest of her site.
I'll leave with a quote that particularly struck me from the AHS talk:
"[P]erhaps these compounds are really only irritants that we've had to evolve to deal with because we happen to eat them, and maybe [it's not the case] that they're actually good for us."