Eat a little, live longer

January 18, 2008
By Syed Akbar
Hyderabad, Jan 16: People, who eat a little, live longer and lead a genetically healthy life.
A study conducted by the University of Hyderabad revealed that people with a low body mass index have the capacity to regenerate their damaged DNA more efficiently than those with normal or high body mass index. As a person grows older, his or her DNA gets damaged. The body repairs the damaged DNA automatically so that the DNA transmits its message effectively to RNA, which in turn issues orders for production of protein molecules for upkeep of an individual.
The system of automatic repair to DNA gets slowed down with ageing which finally leads to death. The experiments carried out on several individuals by the UoH scientists showed that the mechanism of DNA repair is better in people who eat less than those who eat more. Prof Kalluri Subba Rao of the department of biochemistry, UoH, told this correspondent that while scientists in the West had conducted similar
experiments on animal models, the UoH had tested the relation between diet and longevity in human beings.
For the purpose of the study, the scientists selected clinically healthy people. They divided the subjects into three age groups, young (8 to 14 years), adult (20-35 years) and old (above 55 years). They were further classified based on body mass index as normal BMI (more than 20) and low BMI (16 to 18).
"We studied the ability of the peripheral blood lymphocytes from these subjects to respond to PHA (phytohaemagglutinin) stimulation in vitro. We also studied DNA-repair parameters and the function of BMI and ageing," Prof Subba Rao said.
The low body mass index group, considered to be going through chronic but mild under nutrition, showed higher repair capacity and exhibited no appreciable age-depended decline in DNA-repair potential as was seen in normal subjects.
These results correlate well with those seen in unstimulated human lymphocytes and also confirm the observations made earlier in experimental animals, where dietary restriction was shown to have beneficial effects on DNA-repair capacity, he said.
The UoH scientists proved through lab tests one of the central theories that explains the mechanism of ageing process, the DNA-damage and repair theory, that increased DNA-damage and or decreased DNA-repair potential could lead to an accumulation of DNA-damage, ultimately resulting in cellular senescence and death.
Earlier, the beneficial effects of restricted calorie consumption in postponing the ageing characteristics and improving longevity has been demonstrated in a number of species. And now the UoH study had shown that dietary restriction, without malnutrition, retards onset of age-associated diseases in human beings too.
The basal DNA repair in normal body mass index subjects decreased by 18 per cent in old age as compared to adult. In the low body mass index group, however, the UDS (unscheduled DNA synthesis) capacity actually increased with age and the increase was significant in old age as compared to young.