For decades, we’ve heard that calorie restriction might be the proverbial “fountain of youth.” That certainly may be the case for lab animals with shorter life spans, such as mice and rats, which have seen an increase in life span of up to 30 – 40% when fed a restricted diet. But just in time for Healthy Aging Month, new research seems to indicate this may not be the case for humans and instead clarifies that caloric restriction can reduce chronic age-related diseases.
The results of this 25-year-long study, conducted by researchers at the National Institute on Aging (NIA), one of the National Institutes of Health, are published in this month’s issue of the journal Nature.
The research was conducted on four sets of Rhesus monkeys – two experiment groups and two control groups. Of the experiment group, one set consisted of primates aged one to 14 and the other of primates aged 16 to 23. Each group was fed 30% less food than their usual amount. Two similar control groups were fed a diet more consistent with “normal” calories.
At the end of the study, the treated monkeys, regardless of age group, showed no increase in longevity when compared to their untreated counterparts.
There were, however, metabolic and other health benefits. Both male and female primates on the calorie-restricted (CR) diet weighed less than their counterparts in the control group. Triglyceride levels, which increased with age for male and female control-group primates, were significantly lower in the CR monkeys, and male primates on the calorie-restricted diet had significantly lower cholesterol levels.
Additionally, CR primates had significantly lower levels of isoprostane, an indicator of oxidative stress, when compared to the control males. They furthermore showed improved immune response and beneficial effects in T cells.
Caloric restriction also seemed to lower the incidence of cancer. And there was one more encouraging result: age-related diseases such as diabetes, arthritis, diverticulosis, and cardiovascular disease appeared slightly later in the calorie-restricted primates.
The results of the NIA’s monkey experiments contrast with similar research conducted at the University of Wisconsin. In 2009, the Wisconsin study published a paper that showed calorie restriction extended the lives of rhesus monkeys; however, the results excluded non-aging-related causes of death in the calculation. When calculated including all deaths, there was no benefit to longevity.
There are several possible reasons for this disparity in findings. First, while both studies fed the monkeys a diet consisting of 57-61% carbohydrates, the Wisconsin study diet contained 28.5% sucrose versus the NIA study’s 3.9%. The Wisconsin study diet also contained corn starch, which was different from the ground wheat and corn used in the NIA study diet. Additionally, the Wisconsin control primates were allowed to eat as much as they wanted, while the NIA’s control groups were fed a set amount of food.
Study lead author Julie A. Mattison, warns that animal research does not always translate the same in humans, and that there is still much to learn about how to safely benefit from calorie restriction.
The Bottom Line
While calorie restriction may not increase longevity, the key takeaway here is that it can have a beneficial effect on age-related chronic diseases that plague our later years.
Calorie restriction at the best of times is very difficult to achieve, and it can cause harm if not done correctly. And let’s face it – enjoying good food makes life worth living.
Just reducing calories by a bit – not the drastic 10 – 40% required for a calorie-restricted diet – can still have palpable benefits on health. Eating a little less can help with weight control, lower the risk of heart disease, and improve blood pressure. But like most things in life, there is and needs to be balance. Both eating too much and eating too little have been linked to higher mortality, so the focus should be on eating a healthy diet and maintaining a healthful weight.
While most of us would rather live better than live longer (extend our healthspan versus our lifespan), reducing our daily caloric intake isn’t such a bad idea.