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Protein

The word protein comes from the Greek proteos, which means "to come first." It's a fitting name, because protein is a primary ingredient in every cell of the body. Protein is needed to make hair, skin, nails, muscles, organs, blood cells, nerve, bone and brain tissue, enzymes, hormones, antibodies, chemical messengers, and the DNA and RNA used to form the genetic code of life. That's quite a lineup!

All proteins are made from building blocks called amino acids. While there are many different types of protein, there are only about 22 kinds of amino acids. Of these 22, our body can manufacture all but nine. The reason we need protein in our diet is to supply these nine essential amino acids (EAAs). Because most dietary proteins are too large to be absorbed, the body uses its digestive enzymes to separate the food proteins into their individual amino-acid building blocks; only then can they be absorbed and used by the body as raw materials to make the variety of proteins necessary for good health.

Too Little Protein Can Cause Problems
In the developing countries of Africa, Asia, and South America, protein foods are scarce, and deficiencies, when present, can be life-threatening. For generally well-nourished people, a protein intake below required levels will not pose problems if it's only for a day or two now and then. But if the body consistently fails to get enough protein, it will begin showing signs of deficiency.

Depending on the length and degree, symptoms of an ongoing protein deficiency could include: increased susceptibility to disease, fatigue, anemia, hair and skin problems, mental confusion, pallor, digestive disturbances, muscle wasting, weight loss, and eventually death.

Too Much of a Good Thing
As essential as protein is, an excess can cause problems – in the United States, overconsumption is more the norm than the exception. The average individual does not benefit from extra protein, mainly because there is no way to store it for later use. Because the body has an ability to use protein for energy (1 gram of protein yields calories), whenever we overindulge on protein, the body takes the excess, turns it into fat, and stashes it away as stored energy.

What If You Don't Eat Meat?
Most foods have some amino acids. Animal proteins, such as meat, fish, eggs, and dairy products, are complete proteins because they contain all the EAAs. With the exception of soybeans, vegetable proteins such as those from grains and legumes are incomplete proteins, because they lack one or more EAAs. You can easily meet your daily protein requirement by eating only vegetable proteins, however, by combining different foods so that sufficient amounts of all the EAAs are consumed.

There are three basic types of vegetable protein: whole grains (such as rice, corn, oats, and barley); legumes (such as beans and lentils); and nuts and seeds (such as almonds, peanuts, sunflower seeds, and sesame seeds). By planning your meals to include foods from two or more of these groups, you end up creating a complete protein. For example, by eating both rice (grains) and beans (legumes), you supply the body with the daily EAAs it needs.

Putting together this type of "complementary protein" is the essence of vegetarianism. At one time, it was thought that the body needed all the EAAs to be consumed at the same meal. Recently, however, scientists have determined that the body can successfully make protein so long as the full complement of EAAs is present over the course of a day.

How Much Do You Need?
A quick way to estimate your daily protein requirement is to count 11 grams of protein for every 30 pounds of body weight. By this method, a 150-pound adult needs about 55 grams of protein per day. (Note: If you're overweight, use your ideal body weight for this calculation.) Pregnant women should add an extra 10 grams of protein per day, and nursing mothers an extra 12 to 15 grams during the first 6 months. Requirements for children are higher.