18 Jun 2013
PROFESSOR PERMINDER SACHDEV, MD, PhD
Fasting has a long tradition in most cultures and religions. Lord Buddha exhorted his followers to not eat the evening meal, attributing his good health and “of being without illness and of buoyancy and strength” to this practice. Fasting was ritualised in many aspects of Christianity and Judaism, and became the fourth of the five pillars of Islam. Religious fasting was intertwined with ritual and spiritual discipline, and became a form of penitence and identification with the poor and unfortunate.
The health benefits of fasting were not lost on the religious leaders. Ancient practitioners of yoga incorporated fasting firmly into the principles of yogic diet. The scientific study of the health benefits of fasting seriously began in the mid-1930s when Clive McCay and his colleagues published a paper showing that restricting the calories fed to rats in a laboratory, without producing malnutrition, prolonged their lifespan. McCay’s group went on to show that the effect was due to the lower energy consumed and not any other aspects of the diet. In addition to longer lifespans by 20-50%, the rats also had lower rates of cancer. The science of Calorie Restriction (CR) was born. Hundreds of studies since then have shown that CR slows aging not only in mice and rats, but also in yeast, flies, worms and fish. In rats, it was shown that the CR did not have to be continuous, and intermittent ‘fasting’ could produce the same result, as is more likely to occur in humans.
CR was shown to have many other health benefits in rodents. Rates of diabetes, high blood pressure and heart disease were lower, markers of inflammation improved and the heart was younger and more elastic. What about primates? Two studies in rhesus monkeys were initiated in the 1980s, one in Bethesda, Maryland and the other in Madison, Wisconsin, which examined the effect of about a 30% reduction in calories. The Madison study, published in 2009, did not show a significant effect of CR on longevity, but the roughly 50% monkeys still alive tended to live longer. There was however a troubling greater number of non-ageing related deaths in the CR group, which was attributed to an unhealthy diet with a lot of sugar. The Bethesda study concluded that the restricted group lived no longer than the monkeys fed a normal calorie diet, but the CR group was healthier – they weighed less and had lower levels of cholesterol and triglyceride, and slightly lower levels of glucose, and age-related diseases (cancer, diabetes, heart disease) appeared marginally later in them.
How does this translate into humans? One approach has been to examine pockets of exceptional longevity in the world, a well-known one being the Okinawa Island of Japan. These elders are known to practice the Japanese dictum of hara hachi bu (eat until 80% full), but it is not known whether this is the reason that there are more centenarians here per 100,000 residents than elsewhere in the world. The maximum life span has not however been extended in Okinawans. Studies of CR in humans, such as the CALERIE study, have been relatively short–term and have shown benefits on health in terms of lower weight, cardiovascular risk factors and diabetes risk, but the studies have so far mostly recruited overweight people. In another fascinating experiment, eight volunteers lived for two years in a Biosphere – a 3 acre enclosed ecological mini-world – and inadvertently suffered CR. Their weight reduced by about 20%, and there were marked reductions in blood pressure, fasting blood glucose, insulin, cholesterol, thyroid hormone and white blood cells. The message – we cannot be sure that the overall lifespan will increase, but CR is likely to produce significant health benefits and increase the likelihood of reaching the maximum potential age in a relatively healthy state, including a healthy brain without dementia.
In trying to find the mechanism by which CR produces its benefits, scientists have discovered a family of proteins called the sirtuins with a variety of functions in keeping cells healthy. It has been shown that CR leads to an activation of SIRT1, the first and the best-studied sirtuin. Interestingly, SIRT1 is also activated by naturally occurring substances such as phenols, with resveratrol, a phenol present in red wine and berries, being the best known. This raises the possibility that instead of reducing calories, one could achieve the same result by consuming these substances, or even a pill containing resveratrol and similar compounds. Unfortunately, the much touted anti-ageing effects of resveratrol have not been convincingly shown in humans, but a recent report of a number of synthetic compounds with the same effect is keeping the hope of an anti-ageing drug alive.
As of now, all I can suggest is that there may be benefit from eating grapes, berries, sprouted peanuts and dark chocolate, and drinking red wine, but do it all in moderation to keep your calorie intake low. Make sure these calories do not come excessively from carbohydrates or saturated fats. Intermittent fasting is one way of keeping the calorie count down. You may begin your CR with something I learnt from my mother –skip a meal on one day a week.
