Diet to Prevent Alzheimer's?

Summarized by Robert W. Griffith, MD
October 25, 2002 (Reviewed: October 19, 2004)

Introduction

Keeping mice and rats on a low-calorie diet makes them live longer, probably because 'oxidative damage' is lessened. Excess calories and fat are known to promote the production of free radicals, which are normally formed during the process of metabolizing oxygen. These free radicals react with cell membranes, proteins and DNA to cause irreversible damage. They also increase deposits of a protein called amyloid beta in brain tissue. Scientists at Columbia University, New York, have looked at the possible effects of diet on the development of Alzheimer's disease in seniors, and reported their results in the Archives of Neurology.

What was done

Healthy Medicare enrollees living in New York were invited to participate. On entry they had an in-depth interview, a full medical history, a full physical, and battery of mental tests. These examinations were repeated once a year. During the first year they answered a telephone questionnaire about their normal diet.

A group of experts were used to accurately diagnose Alzheimer's disease in participants who developed symptoms, using strict, recognized criteria. The total daily calorie intake, as well as the daily carbohydrate, fat and protein intake, was calculated for each individual from the questionnaires. Participants were allocated to one of four equal-sized groups, called quartiles, according to whether they had low, low-mid, high-mid, or high levels of daily calorie intake. The same procedure was done for carbohydrate, fat, and protein intake.

The genetic make-up of each participant was examined for the presence of the abnormal form of the apolipoprotein E (APOE) gene - the APOE e4 allele. This form, which occurs in about 25% of people, is associated with an increased risk of late-onset Alzheimer's.

What was found

There were 980 participants, whose average age was 75. Two-thirds of them were women; 28% had the APOE e4 gene. During the four years, 242 of them developed Alzheimer's disease.

The frequency of Alzheimer's in the lowest and the highest total calorie quartiles were compared, and it was found that those in the highest quartile were 1.5-times more likely to get Alzheimer's than those in the lowest intake group.

Similarly, there was a 1.4-times increased likelihood of highest quartile fat intake subjects getting Alzheimer's, compared with the quartile with the lowest fat intake.

When analyses were done that included the genetic make-up of the subjects, a clearer picture emerged. In participants with an APOE e4 gene, those in the highest calorie intake quartile were 2.3-times more likely, and those in the highest fat quartile were 2.3-times more likely to develop Alzheimer's disease. On the other hand, participants without the APOE e4 gene were not more likely to get Alzheimer's, whatever their calorie and fat intake.

What to do?

This study shows that a higher intake of calories and fat is associated with a higher risk of Alzheimer disease in people carrying the APOE e4 gene. It's the second study to show such a connection for high fat intake. And it's another example of how genetic make-up may influence the benefits of a dietary regimen - the new field of 'nutrigenomics'.

Before you rush to your physician and ask to have a genetic test, remember three things: first, you have a 3:1 chance of not having the APOE abnormality; second, gene testing is not always easy to get done, and can be expensive; and third, decreasing your total calorie intake and fat intake is almost certainly good for you, whatever its effect on your chances of getting Alzheimer's.

Source

• Caloric intake and the risk of Alzheimer disease. JA. Luchsinger, M-X. Tang, S. Shea,  et al., Arch Neurol, 2002, vol. 59, pp. 1528--1563

Related Links
What is Oxidative Damage?
The Genetics of Alzheimer's, Today