Agriculture and the Paleolithic Diet
[Some thoughts on the merits of Phase 2 Protein Inducers, From "Effects of Dietary Intake of Phase 2 Protein Inducers" available at medscape.com ]
One of the most transforming of human inventions is agriculture. Agriculture allowed rapid expansion of small, formerly hunter-gatherer, populations in a number of centers in Africa, Eurasia, and the Americas. One of the historical consequences of the agricultural revolution was that the variety in food intake decreased as many of these populations became dependent upon relatively few staples, mostly cereals. This decrease in food variety would appear to be greater in colder climates like much of Europe, especially in winter, than in the warmer climates such as found in much of India or Africa. There is ample evidence that development of agriculture was associated with poorer nutrition in various populations, including the Middle East and Northern China.[65-67] This decrease in food variety intake undoubtedly exerted a selective pressure on the genomes of the affected populations. To a great extent, what was gathered by such ancestral hunter-gatherers was a wide variety of roots, nuts, and berries[68,69] (ie, foods rich in dietary phase 2 protein inducers). What would happen if there were a decrease in dietary phase 2 protein inducers in such populations? There should be an increase in tissue oxidative stress. I, therefore, hypothesize that, in agricultural populations, the genotype of those individuals with an increased basal level of expression of phase 2 protein genes would have been selected. I further predict that the selection pressure would possibly have been greater in more northerly populations where there is reliance on even fewer dietary components during the long winter months. If the overall thesis is correct, then it is not unexpected that diseases with an underlying oxidative stress component to them would become more common in populations that were, until recently, hunter-gatherers and now consume a diet more typical of populations that had a long history of agriculture.
Where do we encounter phase 2 protein inducers in our diet? Identified phase 2 protein inducers include: kaempferol,[70] a flavonoid present in high amounts in kale, cauliflower, leek and horseradish[71] and present in small fruits such as gooseberries and strawberries[72]; a flavonoid fraction found in blueberries, cranberries, and bilberries[73]; ellagic acid[74] found in strawberries and raspberries/blackberries; the flavolignan silibinin present in milk thistle fruit[75]; the polyphenolic curcumin found in turmeric[76,77]; sulforaphane[78], a metabolite of the glucosinolate glucoraphanin found in crucifers, particularly in the sprouts of certain broccoli cultivars; and diallyl sulfide[79] found in garlic. Other phytochemicals can also induce the antioxidant response but require higher concentrations (eg, the isoflavone quercetin).[80] Quercetin is found in very high levels in onions and a variety of berries including bilberries and cranberries, with somewhat lower levels in apples, cherries, chokecherries, seabuckthorn berries, and currants.[71,72,81]
To date, most research interest in the area of phase 2 protein inducers has been in the area of cancer prevention.[82] As determined by Dr. Paul Talalay's laboratory, many of the compounds that have anticarcinogenic activities turn out to be phase 2 protein inducers.[83] The anticancer mechanisms involved appear to be related to the ability of phase 2 protein inducers to either decrease the production of strong oxidants or to facilitate scavenging of strong oxidants, hence decreasing the incidence of DNA damage and thereby the likelihood of mutations that promote cancer formation. Induction of phase 2 proteins ought also to decrease problems associated with oxidative stress. Indeed, this is what we observe in stroke-prone spontaneously hypertensive rats fed a diet containing phase 2 protein inducers.[84,85] |
