The co-authors of Invasion of the Prostate Snatchers, blog alternate posts weekly. We invite you to post your comments.

Tuesday, April 29, 2014

The Potential Benefits of Caloric Restriction


There has been a lot written about the benefits to prostate cancer patients of eating mindfully. Boiled down to simplest terms, the notion translates as “Just eat less.”

I am always a bit uncertain when I read how mice prosper on some regime or treatment. Like the diet known as “caloric restriction,” which has all the normal healthy ingredients and food groups, but contains 30 percent fewer calories than usual. A New York Times article of July 10, 2009 stated that “mice kept on such a diet from birth have long been known to live up to 40 percent longer than comparison mice fed normally.”

Well and good. Further up the chain than flatworms. But still a long step from human results with caloric restriction. The next step was to use such a diet with rhesus monkeys to learn whether primates responded the same way as rodents. However, since rhesus monkeys have an average life span of 27 years and a maximum of 40, these experiments require patience.

Dietary restriction seems to set off an ancient strategy written into all animal genomes, that when food is scarce resources should be switched to tissue maintenance from breeding.

The rhesus monkey experiment requires another 15 years before the last monkey is expected to die. An eon, compared to flatworms, which have a life expectancy of about three weeks.

Twenty years after the experiment began, two studies, conducted by a team led by Ricki J. Colman and Richard Weindruch at the University of Wisconsin, reported in Science that the monkeys were showing many benefits, including significantly less diabetes, cancer, and heart and brain disease. “These data demonstrate that caloric restriction slows aging in a primate species,” the researchers wrote, which makes it likely that one could expect the biology of caloric restriction to produce similar benefits for humans.

While caloric restriction holds great promise, few people can keep to a diet with 30 percent fewer calories than usual. So biologists have been looking for drugs that might mimic the effects of caloric restriction, conferring the gain without the pain, so to speak. In recent years researchers have had considerable success in identifying the mechanisms by which cells detect the level of nutrients available to the body. The goal is to find drugs or compounds that trick these mechanisms into thinking that famine is at hand, hence the need for a severely restricted diet.

One such compound is resveratrol, a substance that can, apparently, duplicate in people some of the effects of caloric restriction. A member of a group of plant compounds called polyphenols, resveratrol is thought to have antioxidant properties that protect the body against the kind of damage linked to increased risk for conditions, including cancer since resveratrol is thought to limit the spread of cancer cells and trigger the process of cancer cell death or apoptosis.

The problem was that resveratrol, found primarily in the skin of red grapes (other sources include peanuts and berries) and, hence, in red wine, is present in quantities too small to have any effect, unless you drank about three bottles at a sitting. I have long been a fan of reveratrol, although I have despaired of acquiring enough of the compound to have a measurable effect on my system.

When it comes to resveratrol supplements, there isn't any specific dosage recommendation, and dosages can vary from supplement to supplement, although they are typically far lower than the amounts that have been shown beneficial in research studies. Most supplements contain 250 to 500 milligrams of resveratrol. To get the equivalent dose used in some animal studies, you would have to consume 2 grams of resveratrol (2,000 milligrams) or more a day. Not impossible. And arguably not a risk.

Now, Sirtris, a company based in Cambridge, Mass., has developed several chemicals that mimic resveratrol and can be given in concentrated doses. One such compound, the drug rapamycin, was reported to significantly extend life span in elderly mice, though it is not yet clear whether rapamycin sets off the same circuits as those that increase longevity in caloric restriction when ingested by humans. But there’s hope!

I remember when I was growing up, my Catholic classmates, like Dicky Doyle, ate no meat on Fridays. I reckon that at the very least, the meatless 24 hours gave their digestive systems a rest. Seen as a mild form of caloric restriction, meatless Fridays might well have had an impact on human longevity.

Perhaps if I can find a copy of the Beverly Hills High School alumnae, I can discover who is still around as we enter our 80s. And if they are still in possession of their faculties, perhaps I can learn what and how they’ve been eating for the last half century.

Meanwhile, there is evidence that those of us who eat as our ancestors ate do better in avoiding or fighting a variety of ills, prostate cancer among them.

In my upcoming blogs, I will revisit the eating habits of cave dwellers.

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