Please enjoy this article by David Perlmutter MD :  Author of the grain brain www.davidperlmutter.com 
We’ve all come to accept the notion that our brain will shrink as we age. And nowhere in the brain is this decline more impactful than in the hippocampus, the memory center, one of the primary brain areas that’s first to decline in Alzheimer’s disease.
Researchers measuring the size of the hippocampus show a clear correlation between shrinkage of the hippocampus and declining cognitive function. So, at least as it relates to the hippocampus, size does matter.
However, new and exciting research challenges the notion that this is just a natural part of the aging process and shows that we have the potential to actually grow new cells in this vitally important area of the brain. We can actually expand the hippocampus in size and enhance memory function.
The growth of new brain cells is enhanced under the influence of a specific protein called BDNF. There is no drug that will increase BDNF, but animal research has long recognized that aerobic exercise causes a robust increase in BDNF levels, which increases both the growth of new cells in the hippocampus and boosts memory.
But while animal research has long confirmed the relationship between aerobic exercise and the growth of new brain cells, this relationship has been only recently demonstrated in humans.
Neuroscientist Kirk Erikson and his research team at the University of Pittsburgh, publishing in the Proceedings of the National Academy of Science studied a group of 120 adults for a year. Half the group was given a stretching program to perform three times a week while the other half engaged in three days of aerobics each week.
After one year, the two groups were evaluated looking at three parameters. First, using MRI scans, the change in size of the hippocampus was calculated. Second, serum measurements before and after the trial were measured. And finally, the study measured memory function at the beginning and end of the trial.
The results were breathtaking. While the group doing the stretching program had a decline in memory, hippocampal size, and BDNF levels, the aerobics group showed not only improvement in memory, but an increase in the size of the hippocampus accompanied by an increase in their blood levels of BDNF.
The authors concluded: “These results clearly indicate that aerobic exercise is neuroprotective and that starting an exercise regimen later in life is not futile for either enhancing cognition or augmenting brain volume.”
What’s more, research just published several weeks ago in the Journal of the American Medical Association showed that blood levels of BDNF almost perfectly predict future risk for developing dementia as long as 10 years in the future.
The results of these studies have huge implications. There is no effective treatment for Alzheimer’s disease and yet, simple aerobic exercise can turn on the genetic machinery to manufacture BDNF, the brain’s “growth hormone,” creating new neurons in the brain’s memory center and actually improving memory.
Despite the lack of any pharmaceutical development to enhance this process, you have direct control of your BDNF levels and thus the fate of your brain.
You can increase your BDNF levels and enhance the growth of new brain cells and memory. Here’s how:
  • Engage in regular aerobic exercise. I recommend 20 minutes per day, six days each week. A good target heart rate is around 180 minus your age. Your specific target rate will depend on your level of fitness as well as medications you may be taking.
  • Get your omega-3s. The omega-3 DHA, like aerobic exercise, has been shown to activate the genes that turn on BDNF production. So take a supplement that contains DHA. DHA is available in fish oils as well as algae-derived (suitable for vegetarians). While krill oil is popular, the DHA content is typically only 10% of fish or algae-based products.