X-Message-Number: 24963
Date: Mon, 1 Nov 2004 19:57:34 -0800
Subject: High-fat diet is bad for the brain
From: Kennita Watson <>

 From Nature News:

Published online: 26 October 2004; | doi:10.1038/news041025-11
High-fat diet is bad for the brain
Jim Giles
Animal studies show that fatty food causes cognitive decline.

Now there's one more reason not to eat junk food.
When the star of the movie Super Size Me ate only McDonald's for a 
month, his physical health went down the tube. Now researchers have 
warned that such diets could hit mental abilities too.

Although this idea has been suggested before, a slew of animal studies, 
unveiled on 25 October, all conclude that learning and memory suffer 
when fat intake rises. Rats and mice raised on the rodent equivalent of 
junk food struggle to learn their way around a maze and take longer to 
recall the solution to problems they have already solved, researchers 
said at the annual meeting of the Society for Neuroscience, held in San 

In one experiment, rats were asked to remember the position of 
platforms in a pool of water; the animals are motivated to do so 
because they dislike swimming. Two groups took the test: controls and a 
set that had munched on a high-fat and high-cholesterol diet for eight 
weeks. "Those on the high-fat diet made many more mistakes," says 
Ann-Charlotte Granholm of the Medical University of South Carolina in 

Another study challenged mice to learn how to navigate a maze without 
running over areas that gave them mild electric shocks. When John 
Morley and colleagues at Saint Louis University in Missouri tested the 
mice a week after they had learned the task, those raised on a high-fat 
diet took significantly longer to remember how to avoid the shocks.

Trans-fat trouble

Morley's group speculates that triglyceride, a cholesterol-like 
substance that is found at high levels in rats on a high-fat diet, 
could be causing at least some of the cognitive damage. Morley says 
that when rats take a drug that cuts triglyceride levels but that does 
not cut weight, their performance on the memory tasks improves.

Memory problems have also been documented in diabetics suffering from 
high levels of triglyceride, but both Morley and Granholm say little 
work has been done on the cognitive impact of such diets in humans.

"We believe, on the basis of these data, that high-fat diets are bad 
for cognition," says Barry Levin, a physician at the New Jersey Medical 
School in East Orange. "But we need a note of caution: we work on rats 
and this may not extrapolate to humans."

Granholm says, however, that there is enough evidence for people to 
avoid certain kinds of foods, such as those containing trans-fatty 
acids (trans-fats), which are known to raise levels of triglyceride and 

Trans-fats are found in everything from cereals to margarine and bread, 
and manufacturers prefer them to other fats because they prevent food 
going off. "Decreasing the shelf life of the foods you eat might 
increase your own shelf life," notes Levin.

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