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Studies Suggest Low-Calorie Diets Could Slow Aging
Previous research has shown that calorie restriction may slow aging and increase lifespan in small mammals. But would the same apply to humans? Two recent studies supported by the National Institutes of Health indicate this may be the case.
At Washington University in St. Louis, researchers assessed the diastolic function--how well the heart relaxes between beats--of 25 healthy adults on calorie-restricted (CR) diets and 25 control subjects on typical Western diets (WD). Diastolic function was measured by transmitral flow, Doppler tissue imaging, and model-based image processing of E waves. Subjects in this cross-sectional study also had their C-reactive protein, tumor necrosis factor-alpha, and transforming growth factor-beta1 measured.
Since aging normally causes a decline in cardiac performance, researchers hypothesized that any improvement in diastolic function associated with a CR diet would provide evidence of the diet’s anti-aging benefits.
For 6.5 years, the CR group ate a nutritionally balanced diet providing approximately 1,671 calories per day and at least 100 percent of the recommended daily intake for nutrients. Twenty three percent of the diet’s daily calories came from protein, 49 percent from complex carbohydrates, 28 percent from fat, and 6 percent from saturated fat. The CR diet was low in sodium.
During the same period, the WD group ate a typical diet providing approximately 2,445 calories per day, with 17 percent of its energy coming from protein, 52 percent from carbohydrates, 31 percent from fat, and 11 percent from saturated fat.
Results indicated that long-term CR with optimal nutrition may improve some aging-associated changes in cardiac performance. Specifically, the CR diet improved subjects’ diastolic function by lowering blood pressure and decreasing systemic inflammation and myocardial fibrosis.
Another recent study also suggested that low-calorie diets may affect aging-related factors. Researchers in the Pennington Biomedical Research Center’s Comprehensive Assessment of the Long Term Effects of Reducing Intake of Energy (CALERIE) study conducted a randomized controlled trial to examine the impact of 6 months of calorie restriction on longevity. The CALERIE study, which took place between March 2002 and August 2004, included 48 overweight (non-obese) men and women. Participants were divided into four groups: 1) a control group on a weight-maintenance diet; 2) a group on a 25 percent CR diet; 3) a group on a 12.5 percent CR diet and an exercise program leading to a 12.5 percent increase in energy expenditure; and 4) a very low-calorie diet group.
After 6 months, participants in the three intervention groups had reduced fasting insulin levels and core temperature, two markers associated with increased longevity in humans. In addition, researchers observed a “metabolic adaptation” developed in response to the energy deficit and a possible decline in DNA damage.
References:
Meyer T, Kovács S, Ehsani A, et al. Long-term Caloric Restriction Ameliorates the Decline in Diastolic Function in Humans. Journal of the American College of Cardiology. 2006;47(2):398-402.
Heilbronn L, Jonge L, Frisard M, et al. Effect of 6-month Calorie Restriction on Biomarkers of Longevity, Metabolic Adaptation, and Oxidative Stress in Overweight Individuals. Journal of the American Medical Association. 2006;295(13):1539-1548.
Source: National Institutes of Health
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