Dietary Caloric Restriction Prevents Plasma Melatonin DeclineA study at the Gerontology Research Center in Maryland shows that a calorie restricted diet will prevent the age-related decline in plasma malatonin levels of rhesus monkeys. This study suggests that peak plasma melatonin levels might be useful as a biomarker of aging in humans and other primates. Monkeys subjected to a 30% reduction in caloric intake over a 12 year period maintained younger levels of age-related hormones. Plasma melatonin is a hormone secreted by the pineal gland and several tissues including the gastrointestinal tract. According to the study: A statistically nonsignificant trend toward a progressive reduction with increasing age, as in humans, is observed in fully fed CON animals (Fig. 3A, P < 0.06). In contrast, CR counterparts do not exhibit any hint of an age-related decline. (Note that CON stands for 'control' -- animals on a normal diet, and 'CR' means 'calorie restricted'.) In another group of animals they looked to see if caloric restriction would reverse the age-related decline in this hormone, but found no effect: Data (not shown) from a 12-month CR exposure in both Adult and Old monkeys did not reveal any change in peak melatonin levels. Thus, the CR effect seems to be a chronic reduction or delay in the age-related hormonal decline rather that an acute reversal in old monkeys. Alternatively, a 1-yr duration of CR may not be long enough to affect plasma melatonin levels under the present conditions. Because other research has shown that the effect of caloric restriction is substantially different during the early stages (when weight loss is common, before the body reaches a stasis level) I wouldn't put too much credence in this latter observation. Longer term studies are need in which caloric restriction is begun in middle-aged animals, to see reversal of hormone levels is possible. |
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