CALORIC RESTRICTION and LONGEVITY*
Calorie restriction (CR) extends lifespan and reduces the incidence, and age of onset, of age-related disease in several animal models. For nearly 70 years it has been recognised that a reduction in caloric intake by 30-40% from ad libitum levels (grazing with unlimited food available 24/7) leads to a significant extension of mean and maximal lifespan in a variety of short-lived species.
This effect of CR on lifespan and age-related diseases has been reported in nearly all species tested, and has been reproduced hundreds of times, under a variety of different laboratory conditions. CR also maintains many physiological functions at more youthful levels.
Some of this work was referred to (page 22) in my book How to Live to 100+ Years Free from Symptoms and Disease (see home page). Further research on this aspect of longevity was set out in my August 2005 newsletter Longevity: Recent Research.
Studies in longer-lived species, specifically rhesus and squirrel monkeys, have been underway since the late 1980’s. The purpose was to see if primates responded to caloric restriction in the same way that rodents did. These studies in non-human primates are beginning to yield valuable information suggesting that the effect of CR on aging is universal across species, and that this nutritional paradigm will have similar effects in humans.
This newsletter looks at two of the recently published articles on these monkey studies.
1. Article: Beyond the Rodent Model: Calorie Restriction in Rhesus Monkeys
The first article was published in the journal Age (publisher: Springer Netherlands) in May 2006, titled Beyond the Rodent Model: Calorie Restriction in Rhesus Monkeys. The authors, Doctors M.A. Lane, D.K. Ingram and G.S. Roth, summarise their findings as follows:
“Studies of CR [calorie restriction] and aging using nonhuman primates (rhesus monkeys) were begun several years ago at the National Institute on Aging, the University of Wisconsin-Madison, and the University of Maryland. These studies are beginning to yield useful data regarding the effects of this nutritional intervention in primates. Several studies from these ongoing investigations have shown that rhesus monkeys on CR exhibit physiological responses to CR that parallel findings in rodents. In addition, several potential biomarkers of aging are being evaluated and preliminary findings suggest the possibility that CR in rhesus monkeys could slow the rate of aging and reduce age-related disease, specifically diabetes and cardiovascular disease. It will be several years before conclusive proof that CR slows aging and extends life span in primates is established, however, results from these exciting studies suggest the possibility that the anti-aging effects of CR reported in rodents also occur in longer-lived species such as nonhuman primates, strengthening the possibility that this nutritional intervention will also prove beneficial in longer-lived species, including humans.”
The researchers at the National Institute on Aging did not report the number of deaths in the dieting and normal monkey groups in their publication in 2006. Their findings on this are awaited. However their 2006 publication gives early evidence that CR is beneficial in longer-lived species.
This study was begun more than 20 years ago. Rhesus monkeys live an average of 27 years and a maximum of 40 years. Understandably, these are experiments that require patience!
2. Article: Caloric Restriction Extends Life in Monkeys
The second article was published in Science in July 2009, titled Caloric Restriction Extends Life in Monkeys. The study was conducted by a team led by Doctors R.J. Colman and Richard Weindurch, also at the University of Wisconsin.
This study began in 1989 with 30 adult male monkeys. In 1994, 30 female monkeys and 16 more male monkeys were added the boost statistical power. The monkeys were 7-14 years old when they entered the study. The ‘treated’ group received 30% less calories than the control group which consumed all the food they wanted (grazing). The aim was to see if this CR would delay the aging process and death.
Since the study began, 21 of 38 control monkeys and 14 of 38 calorie-restricted monkeys have died. Of the control monkeys, 14 died of age-related causes, such as cancer, heart disease or diabetes. In the CR group, only 5 died from aging-associated diseases and none have developed the symptoms of diabetes. The remaining deaths, 7 control and 9 CR monkeys, were from complications of anaesthesia, gastric bloat, endometriosis or injury.
In terms of deaths, 37% of the control monkeys have died so far in ways judged to be due to old age, compared to 13% of the calorie restricted group. Dr Weindurch and his statistician, David Allison (University of Alabama, Birmingham) said the “dieting [CR] monkeys were expected to enjoy a life span extension of 10 percent to 20 percent, based on equivalent studies started in mice at the same age.”
Independent of the death rates, the researchers say that the CR monkeys are also showing many beneficial signs including significantly less diabetes, cancer, heart and brain disease. They conclude: “These data demonstrate that caloric restriction slows aging in a primate species.”
Although a smaller number of CR monkeys have died, the difference is not statistically significant, the researchers report.
Some of the monkey deaths were not related to age and could correctly be excluded (although some researchers believe that this should not be done since, in the rodent studies, no differentiation had been made). Some of the monkeys died under anaesthesia given while taking blood samples. Some died from gastric bloat, a disease that can strike at any age, and others from endometriosis. When the deaths judged not due to aging are excluded, the CR monkeys lived significantly longer.
Even if caloric restriction extends longevity in people as well as in rodents, the extent of the effect is unclear. Dr Weindruch believes the effects will be in the same general range as in the primates (monkeys). His monkeys were not started on caloric restriction until 7-14 years of age, and seem to be doing as well as mice that were started at equivalent ages. The most striking extensions of life span in mice occurred when they were put on caloric restriction from birth.
All the monkeys on CR “appear to be biologically younger than the normally fed animals”. (Dr Weindurch)
Were the CR monkeys happy? The article included photos of two monkeys. Canto, aged 27 years on CR diet and Owen, aged 29 years, on normal diet. Canto is thin and looks far from happy, whereas Owen is plump (?overweight) and smiling!
There is another 15 years to go before the last monkey is expected to die.
It is very difficult to keep to a diet with 30% fewer calories/kilojoules than the normal unrestricted intake. Very few will be able to do so. Initially with 30% reduced calorie/kilojoule intake, there will be weight loss, which may be significant especially if the Body Mass Index (BMI) is greater than 25 (overweight) or greater than 30 (obese). (The BMI is the weight in kilograms divided by the height in meters squared.) In time, a new weight will be gained which will be near to lean body mass, BMI between 18 & 20. The restricted intake will then maintain the new lean weight.
Biologists have been looking for chemicals that might mimic the effects of caloric restriction to overcome the difficulty of following a significantly restricted diet. One of these chemicals is resveratrol, a substance found in red wine, though in quantities too small to have a great effect. No doubt research will continue in this area.
In my March 2008 newsletter Prevention of Cancer, the importance of being thin is the Number 1 recommendation for the prevention of cancer: “Be slim, be very slim”. This means having a BMI between 18.5 & 23, depending on body build and bone size (as recommended in the Report). To achieve the desirable BMI, most people initially require calorie restriction to lose weight. To maintain this correct weight needs significantly less calories/kilojoules than would have been consumed before, when at a higher weight, and especially if overweight or obese. To achieve the correct weight (to be thin), as determined by the BMI, should be an absolute goal for everyone.
If some level of further caloric restriction is considered, it is essential that the diet provides adequate and balanced nutrition. Any restriction of calories/kilojoules beyond the desirable BMI (18.5 to 23) must not be so great as to lead to starvation, ie beyond lean body mass. To embark on this, it would be essential to have the supervision of a professional experienced in this area of nutrition.
My book How to Live to 100+ Years Free from Symptoms & Disease (see homepage) sets out the dietary guidelines to help you achieve this longevity. To be thin, and remain thin, is an essential part of the lifestyle to live a long and healthy life.
*Copyright 2010: The Huntly Centre.
Disclaimer: All material in the Huntlycentre.com.au is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.
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