Methionine in Meat, Other Foods May Increase Alzheimer's Risk

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A diet that is rich in methionine, an amino acid found in high levels in fish, red meat, and dairy products, may increase the risk of developing Alzheimer’s disease, according to researchers at Temple University. The research findings were published in the journal Current Alzheimer Research.

Methionine is one of the essential amino acid that the body requires for health but cannot produce itself, so it must be obtained through diet. This amino acid supplies sulfur and other compounds needed for normal metabolism and growth and for producing various antioxidants. It also is a methyl donor, which means it contributes certain molecules required for various chemical and metabolic reactions.

According to the Temple researchers, when levels of methionine are too high, the body attempts to protect itself by transforming it into another amino acid called homocysteine. Previous studies have shown that high levels of homocysteine in humans increase the risk of developing dementia, as well as heart disease and stroke.

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In the new study, the scientists used a mouse model of Alzheimer’s disease and fed one group a diet of regular food for eight months while another group consumed a diet high in methionine. The mice were tested at 15 months of age, which is equivalent to a human at age 70. At the end of eight months, the mice who had consumed the standard diet had normal homocysteine levels while the mice in the methionine diet group had significantly elevated homocysteine levels, similar to human subjects with high homocysteine (hyperhomocysteinemia).

The mice that had high methionine levels also had up to 40 percent more amyloid plaque in their brains, which is a marker of Alzheimer’s disease. When the researchers tested the mice for their capacity to learn a new task, those in the high methionine group had less ability than those in the standard diet group.

Lead researcher Domenico Pratico, an associate professor of pharmacology in the School of Medicine, emphasized that methionine is essential for health and that “stopping one’s intake of methionine won’t prevent Alzheimer’s.” He also noted that “people who have a diet high in red meat, for instance, could be more at risk because they are more likely to develop this high level of circulating homocysteine.” Foods with high methionine levels include fish and other seafood, red meat, ham, poultry, dairy products, sesame seeds, and dried beans.

SOURCE:
Temple University news release, Dec. 15, 2009

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