The latest I've seen on the effect of the Mediterranean diet on age-related mental decline comes from the same research group, at Columbia University in New York, that originally reported that the diet protects against Alzheimer's. A recent study from this team suggests that the Mediterranean diet also protects against the mild cognitive impairment that can develop with age and helps resist the transition from mild cognitive impairment to Alzheimer's disease.
The Mediterranean diet emphasizes high quality fresh fruits and vegetables, nuts, legumes, unrefined cereals, olive oil, fermented dairy products such as yogurt and natural cheese, and fresh fish as daily staples. Red meat is limited to about one meal a month; poultry, eggs and sweets are not daily fare - they're eaten about once a week. Moderate amounts of red wine can be part of the diet.
For the latest study, Nikolaos Scarmeas, M.D. and his team at Columbia looked at adherence to the Mediterranean diet among 1,393 seniors with no cognitive problems and an additional 482 patients with mild cognitive impairment. Over about four and a half years 275 of the 1,393 who initially had no cognitive impairment developed it; among the 482 who started out with mild cognitive impairment 106 went on to develop Alzheimer's.
The Columbia team reported that the closer participants adhered to the Mediterranean diet, the lower their risks. Those who scored highest in adherence (judged on the basis of food frequency questions) had a risk of developing mild cognitive impairment that was 28 percent less than those who scored lowest in adherence. Those who scored in the middle had a 17 percent lower risk.
Of the 482 participants who had some cognitive impairment at the outset those who adhered most closely to the Mediterranean diet had 48 percent lower risk of progressing to Alzheimer's than those who adhered least; those in the middle had 45 percent lower risk than those at the low end of adherence.
I believe the Mediterranean diet protects against Alzheimer's because it is anti-inflammatory. (Anti-inflammatory drugs such as ibuprofen appear to reduce the risk of developing Alzheimer's, and turmeric, a powerful anti-inflammatory agent is also protective.) Inflammation in the brain precedes the tangles of filaments within nerve cells and accumulation of protein plaques outside them that are characteristic of Alzheimer's disease.
My anti-inflammatory diet is similar to the Mediterranean diet in its emphasis on high quality fresh fruits and vegetables, olive oil, yogurt, fresh fish and on vegetable rather than animal protein. I believe an anti-inflammatory diet is even more effective than the Mediterranean diet at moderating inflammation.
Andrew Weil, M.D.