PROTEIN
Protein: On the Scene!
Even though it sounds like just one substance, protein is really a combination of many chemicals called amino acids. Scientists have found 20 different amino acids in protein, and these 20 amino acids can combine in lots of ways - in fact, they have joined together to make thousands of different proteins!
Some types of amino acids are made by you, right inside your body, without you ever thinking about it or doing anything special. These are called nonessential amino acids, and there are 11 of them. And they are necessary - meaning you need them to keep your body in tip-top shape - but they are not essential as part of the food you eat. The essential amino acids - all nine of them - must come from food. That's where eating foods with protein comes in, to give your body the amino acids it needs.
Why Do We Need Protein?
This is one nutrient that's VIP - Very Important Protein! Protein is so
important that your body needed it and used it even before you were born. Your
body uses protein in lots of ways. Protein's biggest job is to build up,
keep up, and replace the tissues in your body. Your muscles, your organs, even
some of your hormones are made up mostly of protein.
Protein helps your body in other ways, too. It likes to make sure things get around by making hemoglobin, the part of red blood cells that carries oxygen to every part of your body. It even makes antibodies, the cells that fight off infection and disease.
PROTEIN
It's easy to get the protein your body needs. Protein is in tasty foods like meat, chicken, fish, eggs, and nuts. And you'll want to say, "More protein, please!" every time you eat some cheese - dairy products like cheese, milk, and yogurt are good sources of protein. And don't forget your bean - your lentil beans or peas!
| Protein: Moving Closer to Center Stage When it comes to nutrients, protein hasn't gotten much attention. Like a quiet child in a classroom of rowdies, it's often been overshadowed by fat, carbohydrates, and vitamins. That's changing. Surprisingly little is known about protein and health. We know that adults need a minimum of 1 gram of protein for every kilogram of body weight per day to keep from slowly breaking down their own tissues. That's about 9 grams of protein for every 20 pounds. Beyond that, there's relatively little solid information on the ideal amount of protein in the diet, a healthy target for calories contributed by protein, or the best kinds of protein. Around the world, millions of people don't get enough protein. This protein malnutrition leads to the condition known as kwashiorkor. Lack of protein can cause growth failure, loss of muscle mass, decreased immunity, weakening of the heart and respiratory system, and death. In the United States and other developed countries, it's easy to get the minimum daily requirement of protein. Cereal with milk for breakfast, a peanut butter and jelly sandwich for lunch, and a piece of fish with a side of beans for dinner adds up to about 70 grams of protein.
All protein isn't alike
Some of the protein you eat contains all the amino acids needed to construct new proteins. This kind is called complete protein. Animal sources of protein tend to be complete. Other protein lacks one or more amino acids that the body can't make from scratch or create by modifying another amino acid. Called incomplete proteins, these usually come from fruits, vegetables, grains, and nuts. Vegetarians need to be aware of this difference. To get
all the amino acids needed to make new protein--and thus to keep the body's
systems in good shape--people who don't eat meat, fish, poultry, eggs, or
dairy products should eat a variety of protein-containing foods each day.
The protein
package Animal protein and vegetable protein probably have the same effects on health. It's the protein package that is likely to make a difference. A 6-ounce broiled Porterhouse steak is a great source of complete protein--38 grams worth. But it also delivers 44 grams of fat, 16 of them saturated. That's almost three-fourths of the recommended daily intake for saturated fat. The same amount of salmon gives you 34 grams of protein and 18 grams of fat, 4 of them saturated. A cup of cooked lentils also has 34 grams of protein, but under 1 gram of fat. The bottom line is that it's important to pay attention to
what comes along with the protein in your food choices. If you are partial
to beef, stick with the leanest cuts. Fish or poultry are excellent
alternatives. Even better options are vegetable sources of protein, such as
beans, nuts, and whole grains. Protein and chronic disease
The most solid connection between proteins and health has to do with a common disorder of the immune system. Proteins in food and the environment are responsible for a variety of allergies. These are basically overreactions of the immune system to what should be harmless proteins. Beyond that, relatively little evidence has been gathered regarding the effect of protein on the development of chronic diseases.
Straight talk about soy The U.S. Food and Drug Administration now allows food makers to claim on the labels of low-fat foods containing at least 6.25 grams of soy protein that soy can help reduce the risk of heart disease. One protein source that has been getting a lot of attention is soybeans. Some research suggests that regularly soy-based foods lower cholesterol, chill hot flashes, prevent breast and prostate cancer, aid weight loss, and ward off osteoporosis. These effects may be due to a unique characteristic of soybeans--their high concentrations of isoflavones, a type of plant-made estrogen.
Heart disease:
There's decent evidence that soy lowers cholesterol levels. A 1995
meta-analysis of 38 controlled clinical trials showed that eating
approximately 50 grams of soy protein a day in place of animal protein
reduced total cholesterol levels by 9.3 percent, LDL cholesterol by 12.9
percent, and triglycerides by 10.5 percent. Such reductions, if
sustained over time, could mean a 20 percent reduction in the risk of
myocardial infarction or other forms of cardiovascular disease.
Individuals with very high cholesterol levels, in the vicinity of 300
mg/dL, appeared to benefit most from eating soy-based foods. Keep in
mind that 50 grams of soy protein is the equivalent of 1½ pounds of tofu
or eight 8-ounce glasses of soymilk a day. The American Heart
Association now recommends including soy-based foods as part of a
heart-healthy diet.
So the news for soy isn't all rosy. Unsettling reports suggest that concentrated supplements of soy proteins may stimulate the growth of breast cancer cells. Too much soy could also lead to memory problems. Among older women of Japanese ancestry living in Hawaii, those who relied on the traditional soy-based diet were more likely to have cognitive problems than those who switched to a more Western diet. These preliminary findings suggest that too much anti-estrogen in the wrong place at the wrong time could be harmful. The Bottom Line-Recommendations for Protein Intake:
Dietary Sources of Protein
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What is Protein?
Take away the water, and about 75 percent of your weight is protein. This chemical family is found throughout the body. It's in muscle, bone, skin, hair, and virtually every other body part or tissue. It makes up the enzymes that power many chemical reactions and the hemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.
Twenty or so basic building blocks, called amino acids, provide the raw material for all proteins. Following genetic instructions, the body strings together amino acids. Some genes call for short chains, others are blueprints for long chains that fold, origami-like, into intricate, three-dimensional structures.
Because the body doesn't store amino acids, as it does fats or carbohydrates, it needs a daily supply of amino acids to make new protein.
Nuts for the Heart:
Many people think of nuts as just another junk food snack. In reality, nuts are excellent sources of protein and other healthful nutrients.
One surprising finding from nutrition research is that people who regularly eat nuts are less likely to have heart attacks or die from heart disease than those who rarely eat them. Several of the largest cohort studies, including the Adventist Study, the Iowa Women's Health Study, the Nurses' Health Study, and the Physicians' Health Study have shown a consistent 30 percent to 50 percent lower risk of myocardial infarction, sudden cardiac death, or cardiovascular disease associated with eating nuts several times a week.
There are several ways that nuts could have such an effect. The unsaturated fats they contain help lower LDL (bad) cholesterol and raise HDL (good) cholesterol. One group of unsaturated fat found in walnuts, the omega-3 fatty acids, appears to prevent the development of erratic heart rhythms. Omega-3 fatty acids (which are also found in fatty fish such as salmon and bluefish) may also prevent blood clots, much as aspirin does. Nuts are rich in arginine, an amino acid needed to make a molecule called nitric oxide that relaxes constricted blood vessels and eases blood flow. They also contain vitamin E, folic acid, potassium, fiber, and other healthful nutrients.
Eating nuts won't do much good if you gobble them in
addition to your usual snacks and meals. At 185 calories per ounce, a handful of
walnuts a day could add 10 pounds or more in a year if you don't cut back on
something else. This weight gain would tip the scales toward heart disease, not
away from it. Instead, eat nuts instead of chips or other, less healthy snacks.
Or try using them instead of meat in main dishes, or as a healthful crunch in
salads