A study conducted by scientists at the Oregon Health Sciences University found that long-term calorie restriction delays age-related change in several measures of immune function in rhesus monkeys. Analysis of the genome of the rhesus monkey shows that humans and the monkeys share about 93 percent of their DNA sequence and shared a common ancestor roughly 25 million years ago.

This investigation began in the mid- to late 1980s when 42 Old World rhesus macague monkeys (Macaca mulatta) were about three to five years of age, about the time of puberty. The monkeys were divided into two groups. Thirteen monkeys received 30 percent fewer calories than the 29 monkeys in the control group. Both groups were given the same vitamins and minerals, and then studied again when they were between 19 and 23 years of age.

Even though these monkeys were the equivalent, in chronological age, to humans in the 60 to 70-year age range, those in the calorie-restricted group exhibited markedly better production and maintenance of naïve T-cells than animals in the control group. Naïve T-cells, the fresh cells in bone marrow, respond to newly encountered pathogens that the immune system has not processed before.

The calorie-restricted monkeys also produced fewer inflammatory cytokines, which are involved in the amplification of inflammatory reactions in the body. Immune aging in mammals is typically accompanied by an increase in inflammatory cytokines, which have been associated with a number of pathologies such as dementia, diabetes, arthritis, neurodegenerative disorders, and coronary vascular disease.

About 95 percent of the research on the biology of aging to date has been done on animals with short life spans. This led scientists to wonder whether low-calorie diets would have the same results in animals with long life spans, such as non-human primates and humans. This investigation provides some of the strongest evidence to date suggesting that calorie restriction could potentially slow immunological aging in people, as well as in laboratory mice and other short-lived animals. The final test of the effect of calorie-restricted diets to improved immunity will lie in future experiments to demonstrate whether these animals are indeed more resistant to pathogens.

What T-cell differences mean in terms of actual lifespan is unclear. Researchers will be following these monkeys until the end of their natural lives. In addition to measuring the length of the monkey’s lifespan, however, researchers are curious about how well the monkeys will age. Specifically, how might this diet affect the monkeys’ eyesight and hearing, their muscle strength and their ability to heal wounds?  Some people believe that if these low-calorie diets slow these common symptoms of aging then that is strong evidence in itself that aging is being slowed, regardless of when life ends, considering that age at death can be influenced by so many factors besides the rate of aging per se.

References:
Messaoudi, J. Warner, M. Fischer, B. Park, B. Hill, J. Mattison, M. A. Lane, G. S. Roth, D. K. Ingram, L. J. Picker, D. C. Douek, M. Mori, and J. Nikolich-Zugich. Delay of T cell senescence by caloric restriction in aged long-lived nonhuman primates. Proc Natl Acad Sci U S A 103 (51):19448-19453, 2006.