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17-Mar-2005

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'Protein police' search your food



When you eat beans and rice, you make the "protein police" in your brain happy because you are eating a meal that supplies the ingredients your body needs to make proteins. These protein ingredients are called "amino acids."
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When you eat beans and rice, you make the "protein police" in your brain happy because you are eating a meal that supplies the ingredients your body needs to make proteins. These protein ingredients are called "amino acids." You need proteins to grow into the next shoe size, to grow into your next hair style and to grow your finger nails. Proteins are also necessary for a wide range of general body maintenance tasks, including the replacement of worn out cells.

In a new study in the 18 March 2005 issue of the journal Science, scientists explain the biological chemistry behind the "protein police" in the brains of mice and rats. If certain amino acids are missing from their food, the rodents' brains can detect the deficiencies 20 minutes after they start eating.

The brain's "protein police" are on the look out for shortages of "essential amino acids" which are protein building blocks that can not be made and must be ingested in food.

Some foods, including many animal products, contain essential amino acids and when the protein police detect these amino acids, they are happy and keep quiet. Most plant proteins, however, are missing at least one of kind of essential amino acid. By combining the right plant foods - like when humans eat beans with rice you can get the right balance of amino acids from plant sources.

If you are lucky enough to have all the beans, rice, tofu, meats, cheeses and grains you could ever want, the protein police in your brain may never take action.

But people with certain health problems, as well as people who have access to a limited variety of foods, may have their food urges influenced by the protein police in their brains.

By studying wild and laboratory animals, scientists are learning more about how the protein police operate to try to avoid amino acid deficiencies.

For example, a rat living inside a warehouse filled with corn has more food than it could possibly eat. Even so, the rat's protein police make it go out and find other food because corn does not provide all the necessary protein-making ingredients.

In the new study, the scientists discovered that animals and yeast use a similar technique to detect protein building blocks.

The fact that many different creatures, from primitive yeast to humans, have a similar ability to detect shortages in protein-making ingredients highlights the importance of maintaining the ability to build proteins.

Making proteins is about number three on the list of most important tasks for an animal's survival, said Science author Dorothy Gietzen from the University of California, Davis in Davis, California. Oxygen and energy are the only more immediate needs most creatures have.

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