Studies show that most short-lived species, such as yeast cells, benefit from calorie-restricted diets. Could the same be true for species that live longer? Researchers in two parallel studies—one conducted by the National Institute on Aging and the other by the University of Wisconsin—explored the life-prolonging and health effects of a calorie-restricted diet in rhesus monkeys but arrived at differing results. To resolve the discrepancy, researchers teamed up to compare their data and study designs.
The University of Wisconsin (UW) study found that rhesus monkeys that were fed a calorie-restricted diet, which contained 30 percent fewer calories than a control group’s diet, survived to about 28 years for males and about 30 years for females—above average for such primates in captivity. In contrast, the National Institute on Aging (NIA) study found no significant effect of calorie restriction on survival.
As they age, rhesus monkeys are vulnerable to many of the same diseases as humans, including cancer, heart disease, and diabetes. Data from both studies showed fewer age-related health conditions in the calorie-restricted groups compared to controls.
In the new study, published online Jan. 17 in Nature Communications, researchers compared data from the two previous studies and provided updated longitudinal comparisons. They presented several factors that likely contributed to the different outcomes, including diet composition, feeding regimens, age of onset, and genetic background.
NIA fed their monkeys a naturally sourced diet comprised of varied protein sources, while the UW diet was purified with limited ingredients and contained a significantly higher amount of sucrose compared to the NIA diet. Additionally, the different timing of feeding and access to food may have also contributed to different results. The UW cohort was more homogenous in age and genetics than the NIA cohort, complicating some comparisons. Finally, the UW monkeys were adults of Indian origin, while NIA’s included both young and old monkeys of Indian and Chinese origin.
Given the similarities between rhesus monkeys and humans, the beneficial effects of calorie restriction on health and life span could also be observed in humans, researchers concluded. However, more research is needed to study how a diet with fewer calories impacts humans as they age.
Reference: Mattison, J.A., et al. Caloric restriction improves health and survival of rhesus monkeys. Nature Communications. 2017;8:14063.