Moderate physical exercise, dietary restriction, and enriched environment stimulation are all known to be good for the brain in general and memory in particular. However, few studies have directly compared these three factors all in the same study, as has been done in the lab of Alois Strasser in the University of Veterinary Medicine in Austria. Moreover, Strasser examined also a brain chemical that is likely to cause some of the brain improvement, the so-called brain-derived neurotrophic factor (BNDF), which sustains neuron life and promotes growth of neuronal processes and synapse formation.
As brain ages, the levels of BNDF typically decline. Several studies have demonstrated that BNDF is important for memory function. Research prior to that of Strasser’s lab showed that exercise “up-regulates” BNDF; that is, exercise stimulates its production. And there had been some indication that environmental enrichment (stimulation, social interactions, etc.) had a similar effect. Therefore, Strasser and colleagues examined the tissue concentrations of BDNF in the cerebral cortex of old rats.
Rats were divided randomly into six groups, living from 5 months up to 23 months. In each age group, rats were divided into those that were given free access to running wheels (RW), forced running on treadmills, food restriction, and sedentary controls with no food restriction. Rats were either either housed individually or in groups of 4 to provide social enrichment. At the end of experiments, BDNF concentrations were determined.
Researchers found higher BNDF concentrations in the 5-month-old animals than in the 23-month-old-animals, suggesting that decline in BNDF accompanies old age and probably accounts for some of the mental decline. Within the older group of rats, sedentary rats that were housed in groups had significantly higher BNDF concentration compared to the old individually caged groups. Their BNDF concentrations were even higher than those of the young baseline group. The results suggest that housing and social interactions have more influence on BDNF concentrations in the cerebral cortex of aging rats than do physical exercise and food restriction.
There was some benefit of the exercise, but only from forced running on the treadmill, not voluntary activity. However, other studies had established that even voluntary exercise by old animals increased BNDF in other parts of brain, including the area so crucial to memory formation, the hippocampus.
The lack of beneficial effect of caloric restriction in sedentary rats to weight levels matching those of the voluntary exercise group was somewhat unexpected. Prior studies in other labs had shown that such restriction does promote synaptic plasticity and even birth of new neurons. Thus, there are no doubt multiple influences that can be beneficial to brain that are not mediated by BNDF. So, to the extent that these results can be extrapolated to aging humans, it would seem like a good idea to:
- Exercise regularly and vigorously (assuming you don’t have heart trouble or other conditions that would prevent it)
- Lose weight
- Get out of the house and socialize.
Strasser, A. et al. 2006. The impact of environment in comparison with moderate physical exercise and dietary restriction on BNDF in the cerebral parietotemporal cortex of aged Sprague-Dawley rats. Gerontology. 52: 377-381.