Whether or not you've tried a low-carb, high-protein diet, you've probably wondered if you should. In many ways, high-protein diets have lived up to their promises: People have lost pounds without going hungry. Yet research has shown that such diets may not help you permanently thwart unwanted weight any better than more balanced ones. In fact, in the long run they may actually damage blood vessels.

“High-protein diets interfere with Mother Nature's checks and balances,” says Eileen Vincent, MS, RD, assistant director of clinical and nutrition research at Northwestern University's Feinberg School of Medicine in Chicago. So how much — and what kind of — protein is really best for overall health?

The protein conundrum

“Protein is the second most important nutrient,” says Katherine Tallmadge, MA, RD, author of Diet Simple (LifeLine, 2002). “Only water is above it.” Protein provides needed calories, as well as necessary amino acids to build and maintain muscle mass. It's also a major structural and functional component of every cell in your body. It is a force in your organs, your skin, your bones, your muscles, and your brain. In other words, you can't live without it.

Millions of dieters have been wooed by protein as a purportedly effective way to lose weight without major sacrifice. Considering that obesity affects one-third of Americans, it's no wonder so many people have given high-protein diets a try. The science is pretty simple: Your body burns carbohydrates before fat for energy. By reducing carbs and eating more protein and fat, you burn stored body fat more efficiently, and thus drop weight.

But breaking down carbs is much simpler for the body than digesting proteins. When you eat protein, your body works harder to process the nutrient, according to Debra Boutin, MS, RD, an assistant professor at Bastyr University in Kenmore, Washington. If you down too much protein, you may overtax the body, making it difficult to eliminate the nutrient's by-products.

Whether you're trying to lose weight or simply enhance your overall health, a balanced diet seems to be a safe bet, says Boutin. “Protein has this magical aura around it. People think they need more than they do. You need to have a nice balance of proteins, fats, and carbohydrates. The key to weight loss is to stay active: Eat less and move more.”

How much do you really need?

The USDA recommends that the average healthy adult get 10 percent to 35 percent of his or her calories from protein, or 0.8 grams of protein per kilogram of ideal body weight. To calculate your daily protein needs, divide your weight in pounds by 2.2 to calculate your weight in kilograms. For a 150-pound woman, multiply your weight (68 kilograms) by 0.8. That comes to about 55 protein grams a day — not much when you consider that a 3-ounce portion of fish or chicken (about the amount that fits in the palm of your hand) contains approximately 21 grams of protein.

Both Boutin and Vincent agree that most Americans eat too much of the nutrient. For example, a heart-healthy portion of salmon is 3 ounces, says Vincent, but most people down 6-8 ounces at a sitting, which nearly meets or exceeds your daily requirement for protein. To visualize your counts, Vincent suggests dividing your plate into four parts: one-fourth should be protein (meat, fish, poultry, or a plant-based source such as beans), and the rest should include a mix of vegetables, fruits, and whole grains.

And because every rule has at least one exception, some people don't always get enough protein. People over 60 and dieting women who don't follow a high-protein plan are at the highest risk for protein deficits, says Tallmadge. According to her, 30 percent of women and 20 percent of men over age 20, and 40 percent of men and women over age 70, fall below the recommended daily allowances for protein. “A protein deficiency affects bone health, muscle mass, and immune function,” says Tallmadge.