Restricted Diet Increased Life Span In Monkeys – Will It in Human?

The study is about the relationship between diet and life span. In 1989, a longitudinal study was started to determine whether restricted diet is linked to the incensement of life expectancy in monkeys. According to previous research, dietary restriction (RD) slows the aging process in laboratory mice and rats based on its ability to oppose the development of a broad spectrum of age-associated diseases and extend maximum lifespan. Moreover, the maximum life span of non-mammals is also increased by dietary restrictions.

Life expectancy (the average life span) greatly increased during the 20th century in most countries, largely due to improved hygiene, nutrition, and health care. One possible approach to further increase human life span is “caloric restriction.” But does restricted diet have similar action in a primate species? Like Monkeys? Would RD enhance monkey’s lives?

Some of the purposes of the study is to advance the development of the rhesus monkey as a model for the study of aging. Second, determine the influence of DR on the rate of aging in this primate species. Could the model “restricted diet” be applied on human in order to increase our life span, and improve the quality of our lives?

The initial study began in 1989 to investigate the effects of a 30% DR in 30 adult male rhesus monkeys. In 1994, an additional 30 females and 16 males were added to the study.

The team followed a restrict methods and procedures to carry on the study, because it’s a longitudinal study that is going to take more than 30 years. The independent variable is diet or dietary restriction and the dependent variable is life span. The study was conducted under several conditions and methods:

A. Environment:

The monkeys had extensive visual and auditory contact with other monkeys. The animals were allowed continuous access to water, and the animal rooms were maintained at 21±26C with, 50±65% relative humidity. Artificial room light is automatically controlled to provide 12-h light and dark period.

B. Health Care Routine:

The monkeys were tested daily for health problems, injuries or any other complications. Among the 12 controls in Group 1, three animals became pre-diabetic versus none in the DR group.

C. Diet:

All animals were fed a semi-purified diet which contains 15% lactalbumin, 10% corn oil and approximately 65% carbohydrate in the form of sucrose and corn starch. The macronutrient composition of the restricted and control diets is similar, but the restricted diet is supplemented with an additional 30% of the vitamin and mineral content to ensure that the groups, on average, consume a similar amount of micronutrients. Food intake is measured for each animal daily. All animals are fed in the morning and, at approximately 4 PM, any food remaining in each cage is removed and weighed. Intakes for individual animals are averaged weekly and summarized over a six-month period. The research team reduced the RD group by 30 percent over the first three months, but 30% percent diet reduction was too much for two of the animals because their body fat decreased to 3% followed by pale face, illness, and hair lost. The team decided in 1996 to increase the daily food intake to these animals in order to increase their body fat to 5% to maintain healthy body.

D. Measurements and calculations:

Most measurements are completed annually within a single, six-week assessment period. During Week 1, blood samples are collected for CBC, chemistry panels, endocrine measurements and measurement of skeletal parameters. DXA measurements of body composition are also completed during Week 1. Urine collections are completed during Week 4 and indirect respiration calorimetry measurements of energy expenditure are completed in Week 5. Finally, during Week 6 of the assessment period, a frequently sampled intravenous glucose tolerance test
(FSIGT) is done.

Conclusion and Results:

As expected the RD groups showed significant difference in body weight compared to the control group. They also were at much lower risk of developing bone disease, because Osteoblast was stimulated to produce more boney matrix which make bone much denser and stronger.

It has also been proposed that aging is the result of accumulated damage caused by oxygen free radicals produced during aerobic metabolism. The DR group was more active and had higher energy than the control group; this would help minimize the free radicals, thus; slow that aging process. RD helped the monkeys to walk, behave, and think much effectively than control group when they closely monitored after and before the meals. Bad cholesterol was reduced during the experiment which results in healthier heart, and less chances of heart diseases.

“A 20-year study found that Rhesus monkeys fed a nutritious, low-calorie diet have fewer age-related diseases than counterparts on a normal diet, also, results show that calorie restriction helps preserve primates’ bodies and brains”, says Luigi Fontana, of Washington University in St. Louis. Life span of Rhesus monkeys is 40 years, but with the RD experiment, some of the monkeys like Owen 25 years old slowed his aging process significantly. 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 calorie-restricted group, only five died from aging-associated diseases, and none have developed symptoms of diabetes.

Did the scientists answer the questions? Did they accomplish the goal? Yes, indeed, now they are even more convinced that RD slows the aging process in Monkeys, and they strongly believe that it will on human.