The Sirtfood Scam
Epigenetics and Aging (13)
There are two diets for which there is something approaching a consensus as to their healthfulness: the Mediterranean Diet and the Okinawa Diet. The latter is often generalized to the Japanese, or even Asian Diet. The two diets have interesting similarities, as well as some differences, more fermented foods in the Okinawa diet, for example. But both are largely plant-based, lots of fresh fruits, vegetables, and whole grains. Because of the high plant content, these diets are also high in polyphenols.
Polyphenols are a large and diverse group of plant secondary products. They are called secondary products because they are not required for plant growth. But they are essential in protecting a plant from UV damage, as well as a host of plant predators and pathogens, from fungi to insects. They are found in every plant tissue, leaves, flowers, fruits, seeds, bark and roots. While bad for insects, polyphenols are generally considered healthful in humans. Most food-born polyphenols are flavonoids. Stilbenes are a much smaller group of polyphenols, which includes resveratrol.
Western diets that emphasize polyphenol rich foods were only in part inspired by the Mediterranean Diet and Okinawa Diet, more so by research demonstrating the antioxidant effects of polyphenols, later by more questionable claims about polyphenols as antidotes for inflammation and other age-related forms of decline.
So-called sirtfoods comprise the latest fad diet. The premise of the Sirtfood Diet is that foods high in polyphenols are good because polyphenols activate sirtuins. It looks a lot like the Western Polyphenol Diet but with a few twists.
A Western Polyphenol Diet includes these foods:
Kale
Red wine
Strawberries
Blueberries
Other fruits
Onions (red or yellow),
Soy
Chile
Extra virgin olive oil
Coffee
Dark chocolate
Green tea
Black tea
Red chicory
Arugala,
Walnuts
The Sirtfood Diet includes these foods:
Kale
Red wine
Strawberries
Blueberries
Red onions
Soy
Extra virgin olive oil
Coffee
Dark chocolate (>85% cocoa
Buckwheat
Turmeric
Green Tea (Matcha)
Bird’s eye chili
Walnuts
Arugula (rocket)
Lovage
Dates (medjool)
Coffee
Red chicory
Capers
Not a lot of space between these two diets. But one is formulated for its antioxidant value, the other to stimulate sirtuins and their putative multimodal anti-aging effects. The main differences are that the Sirtfood Diet includes medjool dates, buckwheat and capers, while the Western Polyphenol Diet has a lot more foods that I have not listed, including all berries, most other fruits, most vegetables, legumes other than soy (such as broad beans and peanuts), grains (whole wheat, rye etc.). Oh, and the Western Polyphenol Diet is not so as specific about the arugula, onions or the tea (doesn’t have to be green, and if green, doesn’t have to be matcha). So, the Sirtfood Diet is basically the Polyphenol Diet writ small.
The French Paradox
The story of resveratrol is representative of the evolution of polyphenols in public awareness. It started with the French Paradox, the counterintuitive seeming diet of many French people, who consume lots of fatty food but have a low incidence of heart disease. The secret, it was postulated, was the red wine that they also consumed with many meals. Red wine as a secret to good health came as welcome news to many, including me. (If only white wines provided the same benefits.)
But what was in red wines—and not whites—that was so healthful? It had to be in the skins, with which reds—but not whites—are fermented. Resveratrol emerged as the prime candidate, first as a powerful antioxidant, then, infamously, as the main actor in calorie restriction by way of its putative role as a sirtuin activator. The fact that red wine remains on the sirtfood lists reflects the latter. But why medjool dates? Why capers? Why only matcha green teas to the exclusion of all others.? Why only the bird’s eye chili of all possible chili varieties?
Medjool dates are rich in diverse polyphenols, but I have seen no comparisons with other date varieties; capers have an abundance of, kaempferol, but kale and spinach have that covered. Green teas have a somewhat different assortment of polyphenols than black teas. One, called EGCG (epigallocatechin) is particularly in vogue at present. Matcha green teas have the most EGCG because the finely ground leaves remain in the tea when consumed. But EGCG is also abundant in apples, apricots, blackberries cherries, broad beans, chocolate and a whole lot more. As for the fixation on bird’s eye chilis, I haven’t a clue. But I would wager that it has no more polyphenols than your average habanero. Moreover, many other spices are loaded with polyphenols, including clove, oregano, and thyme.
There is little evidence that EGCG or any other polyphenols are important sirtuin activators; that includes, of course, resveratrol. Moreover, there are reasons, based on basic metabolic considerations, to doubt their efficacy in that respect. All polyphenols are quickly broken down into their constituent chemicals once ingested. That is, their bioavailability is fleeting compared to known sirtuin activators such as AMPK (adenosine monophosphate-activated protein kinase), which is produced within cells in many tissues all the time. (AMPK is also available as a superfluous supplement.) Then there is the cofactor, NAD*, without which sirtuins are functionally inert, more on which in the next post.