Thursday, January 29, 2009

PNAS Study Finds CR Benefits Memory

Monday I posted this, noting the exciting advances being made with sirtuin activating compounds (which mimic calorie restriction) that could decelerate human aging, thus delaying all the afflictions that currently ravage most humans in their 60's, 70's, and 80's.

Now sceptics typically raise the following two concerns (amongst others)-- (1) we still do not know what the impact of calorie restriction is on humans (in terms of health and longevity benefits) and (2) keeping the body healthy as we age is only of limited value if our minds are not also kept healthy. Well, this study published this week in the Proceedings of the National Academy of Science should help ease both of these sceptical worries. The study found that calorie restriction actually improves the memory of elderly humans. This provides yet further reason for us to get behind the science that could lead to a safe and effective pharmaceutical intervention that mimics the effects of calorie restriction! Here is the abstract:

Animal studies suggest that diets low in calories and rich in unsaturated fatty acids (UFA) are beneficial for cognitive function in age. Here, we tested in a prospective interventional design whether the same effects can be induced in humans. Fifty healthy, normal- to overweight elderly subjects (29 females, mean age 60.5 years, mean body mass index 28 kg/m2) were stratified into 3 groups: (i) caloric restriction (30% reduction), (ii) relative increased intake of UFAs (20% increase, unchanged total fat), and (iii) control. Before and after 3 months of intervention, memory performance was assessed under standardized conditions. We found a significant increase in verbal memory scores after caloric restriction (mean increase 20%; P < 0.001), which was correlated with decreases in fasting plasma levels of insulin and high sensitive C-reactive protein, most pronounced in subjects with best adherence to the diet (all r values < −0.8; all P values <0.05). Levels of brain-derived neurotrophic factor remained unchanged. No significant memory changes were observed in the other 2 groups. This interventional trial demonstrates beneficial effects of caloric restriction on memory performance in healthy elderly subjects. Mechanisms underlying this improvement might include higher synaptic plasticity and stimulation of neurofacilitatory pathways in the brain because of improved insulin sensitivity and reduced inflammatory activity. Our study may help to generate novel prevention strategies to maintain cognitive functions into old age.

Studies like this raise so many fascinating issues. Contrast, for example, these findings with the ones I noted earlier-- that postnatal poverty affects the brain development of children. Now everyone is going to want to prevent the adverse impact poverty has on the brain development of children. But what about the adverse impact these same people could be vulnerable to later in life? Should we not also want to benefit their cognitive capacities at *all* ages, not just early in life? And should we not seek to mitigate the internal vulnerabilities of our biology rather than just those external environmental factors that can harm our cognitive capacities? Once we overcome "ageism" and the shortsightedness of worrying exclusively about external threats to our health prospects (rather than the evolutionary causes of the diseases of aging) we will be better positioned to take a truly inclusive approach to improving the health prospects of the world's populations this century.