Expert Commentary: Brandon Colby, MD, M.B.A. 9/15/2009

However, physical activity has even greater beneficial effects on the brain by improving synaptic plasticity (i.e. neurons in the brain are able to communicate better with each other) and even stimulates the growth of neurons. Because of this, physical exercise adds to a person’s cognitive reserve, which can be thought of as their reservoir of neurons in the brain. Certain factors make the reservoir lose neurons faster, such as a sedentary lifestyle and smoking, which other factors slow down the rate of lose, such as recreational physical activity, mental exercise, and Mediterranean-type diets. The Mediterranean-type diet most likely protects against Alzheimer’s because it is high in antioxidants while being low in saturated fats and overall calories.
 
The reason why this study is so important because it is one of the first to look at the outcome when both Mediterranean-type diet and physical activity are combined together. Before this study it was postulated that both will probably help more than either alone but this study proves it – not only that, but both together appear to have a multiplicative effect whereby the risk of Alzheimer’s is reduced by over 85 percent, which is amazing. However, the number of people in this study was relatively low so it will be good to see these results replicated in a larger population.
 
And although there were equal numbers of people genetically predisposed to Alzheimer’s (people who have a specific variant called APOE4), I’d like to see this study conducted to assess long-term Alzheimer’s disease risk in people who were genetically predisposed to Alzheimer’s due to genetic variants in their APOE and TOMM-40 genes. These people are at extremely high risk of Alzheimer’s and they are the ones that can benefit the most from aggressive prevention throughout life, such as diet and exercise combined together.
 
For people who aren’t predisposed to Alzheimer’s either diet or exercise seem to be excellent and the choice really is personal preference. Of course both together would be optimal but realistically most people aren’t going to do both over the long-term, especially if they aren’t genetically predisposed to the disease. It is all about slowing down the loss of neurons from the neuron reservoir we have in our brain – on their own, each of these preventive strategies will slow down that loss and both together will slow it down tremendously.

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