Lifespan. David Sinclair
Читать онлайн книгу.
and sex—the poor guy—and resolved to limit himself in each regard. The historical record is a bit vague on the details of his sex life after that fateful decision,110 but his diet and drinking habits have been well documented: he ate no more than twelve ounces of food and drank two glasses of wine each day.
“I accustomed myself to the habit of never fully satisfying my appetite, either with eating or drinking,” Cornaro wrote in his First Discourse on the Temperate Life, “always leaving the table well able to take more.”111
Cornaro’s discourses on the benefits of la vita sobria might have fallen into obscurity had he not provided such compelling personal proof that his advice had merit: he published his guidance when he was in his 80s, and in exceptional health, no less, and he died in 1566 at nearly (and some sources say more than) 100 years old.
In more recent times, Professor Alexandre Guéniot, the president of the Paris Medical Academy just after the turn of the twentieth century, was famed for living on a restricted diet. It is said that his contemporaries mocked him—for there was no science at that time to back his suspicion that hunger would lead to good health, just his gut hunch—but he outlived them, one and all. He finally succumbed at the age of 102.
The first modern scientific explorations of the lifelong effects of a severely restricted diet began during the last days of World War I. That’s when the longtime biochemical collaborators Lafayette Mendel and Thomas Osborne—the duo who had discovered vitamin A—discovered, along with researcher Edna Ferry, that female rats whose growth was stunted due to lack of food early in life lived much longer than those that ate plenty.112
Picking up on that evidence in 1935, a now-famous Cornell University professor named Clive McCay demonstrated that rats fed a diet containing 20 percent indigestible cellulose—cardboard, essentially—lived significantly longer lives than those that were fed a typical lab diet. Studies conducted over the next eighty years demonstrated again and again that calorie restriction without malnutrition, or CR, leads to longevity for all sorts of life-forms. Hundreds of mouse studies have been done since to test the effects of calories on health and lifespan, mostly on male mice.
Reducing calories works even in yeast. I first noticed this in the late 1990s. Cells fed with lower doses of glucose were living longer, and their DNA was exceptionally compact—significantly delaying the inevitable ERC accumulation, nucleolar explosion, and sterility.
If this happened only in yeast, it would merely be interesting. But because we knew that rodents also lived longer when their food was restricted—and later learned that this was the case for fruit flies, as well113—it was apparent that this genetic program was very old, perhaps nearly as old as life itself.
In animal studies, the key to engaging the sirtuin program appears to be keeping things on the razor’s edge through calorie restriction—just enough food to function in healthy ways and no more. This makes sense. It engages the survival circuit, telling longevity genes to do what they have been doing since primordial times: boost cellular defenses, keep organisms alive during times of adversity, ward off disease and deterioration, minimize epigenetic change, and slow down aging.
But this has, for obvious reasons, proven a challenge to test on humans in a controlled scientific setting. Sadly, it’s not hard to find instances in which humans have had to go without food, but those periods are generally times in which food insecurity results in malnutrition, and it would be a challenge to keep a test group of humans on the razor’s edge for the long periods of time that would be required for comprehensive controlled studies.
As far back as the 1970s, though, there have been observational studies that strongly suggested long-term calorie restriction could help humans live longer and healthier lives, too.
In 1978 on the island of Okinawa, famed for its large number of centenarians, bioenergetics researcher Yasuo Kagawa learned that the total number of calories consumed by schoolchildren was less than two-thirds of what children were getting in mainland Japan. Adult Okinawans were also leaner, taking in about 20 percent fewer calories than their mainland counterparts. Kagawa noted that not only were the lifespans of Okinawans longer, but their healthspans were, too—with significantly less cerebral vascular disease, malignancy, and heart disease.114
In the early 1990s, the Biosphere 2 research experiment provided another piece of evidence. For two years, from 1991 to 1993, eight people lived inside a three-acre, closed ecological dome in southern Arizona, where they were expected to be reliant on the food they were growing inside. Green thumbs they weren’t, though, and the food they farmed turned out to be insufficient to keep the participants on a typical diet. The lack of food wasn’t bad enough to result in malnutrition, but it did mean that the team members were frequently hungry.
One of the prisoners (and by “prisoners” I mean “experimental subjects”) happened to be Roy Walford, a researcher from California whose studies on extending life in mice are still required reading for scientists entering the aging field. I have no reason to suspect that Walford sabotaged the crops, but the coincidence was rather fortuitous for his research; it gave him an opportunity to test his mouse-based findings on human subjects. Because they were thoroughly medically monitored before, during, and after their two-year stint inside the dome, the participants gave Walford and other researchers a unique opportunity to observe the numerous biological effects of calorie restriction. Tellingly, the biochemical changes they saw in their bodies closely mirrored those Walford had seen in his long-lived calorie-restricted mice, such as decreased body mass (15 to 20 percent), blood pressure (25 percent), blood sugar level (21 percent), and cholesterol levels (30 percent), among others.115
Конец ознакомительного фрагмента.
Текст предоставлен ООО «ЛитРес».
Прочитайте эту книгу целиком, купив полную легальную версию на ЛитРес.
Безопасно оплатить книгу можно банковской картой Visa, MasterCard, Maestro, со счета мобильного телефона, с платежного терминала, в салоне МТС или Связной, через PayPal, WebMoney, Яндекс.Деньги, QIWI Кошелек, бонусными картами или другим удобным Вам способом.