The most common question that I am asked is  “What can I do to prevent Alzheimer’s disease?”    The honest answer is that nobody actually knows.  Much of what we read or hear on the news is overstated for emphasis.  Our current beliefs are mostly based on anecdotal reports, marketing, and epidemiological studies (looking backwards to see what someone says they did) with a few prospective studies (ongoing studies of people as they age) to add intrigue. 

There are few randomized control studies (the gold standard for scientific inferences of cause and effect) to guide us in answering this important question.  Epidemiological studies tell us what is correlated or associated with desired outcomes.  However, they cannot tell us root causes.

It seems intuitively sensible that what we eat is important for our health and may impact the course of neurodegenerative disorders.  Indeed there are epidemiological studies on a number of nutritional choices.  I found a recent review that was helpful: “Nutrition and the risk of Alzheimer’s disease” (Biomed Research International, 2013, 2013, article ID524820).

On a global level, there is an association of being overweight/obese with Alzheimer’s disease.  But the relationship is complicated.  It appears that being overweight in middle age increases (does not cause) the risk of Alzheimer’s disease in old age.  However, being overweight in late life reduces the risk.  This finding may stem from the typical weight loss in those who have Alzheimer’s disease in late life.

There are numerous nutrients that have been explored: vitamins A C, E, B, D; metals, copper, fatty acids, carbohydrates, fish consumption, fruits, vegetables, dairy, coffee, and tea.  There are very few randomized control studies in humans to guide us.  The findings are correlational and complex with little quality supportive evidence for any of these nutrients taken alone.  Mostly, the findings support the fact that deficiencies in nutrients such as vitamins and minerals cause problems in cognition and may be correlated with the risk of Alzheimer’s disease.

Another approach to the question of nutrients has been to study dietary strategies including the Western diet (red and processed meats, refined grains, sweets, ad desserts), Japanese diet (fish and plant foods), “Healthy diet,” DASH (Dietary Approaches To Stop Hypertension), and Mediterranean diet.  Again there are no randomized clinical trials to draw from but correlational findings support an eating strategy such as the Japanese, Mediterranean/DASH/Healthy diet.

In conclusion, there are no hard facts about the causal link between nutrition and Alzheimer’s disease. Participants in epidemiological studies may not be the same as the “average” resident in the United States.  They may be generally more health conscious beyond just nutrition.  There is no clear guidance about doses of supplements to take other than that too little is a problem as is too much.  We would obtain better guidance from randomized clinical trials but these are not generally feasible and who really wants to be in a placebo group for this type of study?  Furthermore, trials would need to extend over decades to provide meaningful guidance about Alzheimer’s disease as it takes decades to unfold.  Finally, prevention must start even before there are even subtle symptoms if it is to be effective.

We must decide on nutritional strategies based on mostly epidemiological studies and faith.   I am betting on the Japanese, Mediterranean/DASH/Healthy diet that makes fruits, vegetables, and fish as the best approach to nutrition.  There just doesn’t seem to be any good evidence that supplements are useful in people who are not deficient or malnourished.