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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.

How often should you eat protein?

Regardless of how much protein you eat, you need to make it part of every meal. Why? There are two reasons, explains Vincent: For one, your body can process and absorb only so much protein at one time. And second, a fat-protein combo slows digestion, which helps control blood sugar levels and leaves you feeling full longer. Legumes — which are low in fat but high in fiber and protein — have a similar effect on blood glucose as foods with the fat-protein combo, says Boutin. “Water-soluble fiber absorbs water along the gastrointestinal tract, slowing the movement of digested food through the intestines, and thereby slowing the release of glucose into the bloodstream.”

What kind should you eat?

Not all protein is created equal; some sources are complete, others are not. “In the United States, we tend to eat more animal protein,” says Boutin. “But plant sources of protein can support us just as well.”

Vegetarians, take note: According to once-upon-a-time logic, meat-free folks had to carefully combine foods to get a complete spectrum of amino acids at each meal. Remember the ol' “beans-and-rice” notion? A well-planned vegetarian diet isn't a bad idea, of course, but strict mealtime food combining isn't critical.

“As long as you have a range of amino acids in a 24-hour period, your body will manage just fine,” says Boutin. If you eat dairy, grains, legumes, nuts, and seeds each day, you'll cover the essential aminos. But if you're allergic to nuts or don't do dairy, you might want to consider consulting a nutrition pro. Some examples of amino-balanced meals include mixtures of grains and legumes (seven-bean soup and whole-grain toast or lentil curry over rice), and seeds and legumes (hummus and falafel or bean cassoulet topped with roasted pumpkin and sunflower seeds).

And meat eaters may want to double-think that daily double cheeseburger in favor of more variety. According to Boutin, the USDA dietary guidelines lump together meat, poultry, seafood, legumes, nuts, seeds, and eggs because they share something in common: protein. But each food type offers unique nutrients. For example, pork is rich in iron, and some fish boast omega-3 fatty acids. So eating an array of these foods (5-6 ounces per day of any combo of protein foods is enough) will offer the biggest health bang for your bite and keep you from overdoing the bad stuff like saturated fat, which lurks most often in red meat and whole-dairy products. According to USDA guidelines, saturated fat should make up less than 10 percent of your daily calories.

Back to balance

In fact, no matter who you are, if you eat a mix of foods, you'll generally be OK. “We focus so much on nutrients,” says Boutin. “We had the bad-carb phase and a bad-fat phase. Now I'm waiting for the bad-protein phase. If you treat your diet like a triangle of needs — protein, fats, and carbs — and you eat a variety of foods that contain protein, then you'll be fine.”

Freelance writer Pamela Bond hopes a bad dark-chocolate phase never happens.

To calculate your protein needs, multiply your body weight in kilograms (pounds divided by 2.2) by the amount of protein per kilogram listed here.

Daily protein needs

  GRAMS OF PROTEIN PER KILOGRAM NOTES
1 year to 3 years 1.10
4 years to 13 years 0.95
14 years to 18 years 0.85
18 years and older 0.80 Amount based on average inactive adult.
Pregnant adult women 1.10 Amount based on prepregnancy body weight.
Athletic adults 1.20-1.40 Amount for those who work out actively five days per week. Eat a snack of protein and carbs in a ratio of 1:4 (such as milk and cereal) within 30 minutes after exercise to replenish energy stores and help build muscle.
Vegetarian adults 0.80 Vegetarians need to combine protein sources to get adequate essential amino acids.
60 years and older 0.80 Some experts think the daily intake should go up to between 1.0 and 1.4 grams. It's best to get assessed for your individual needs.
Sources: Debra Boutin, MS, RD; Eileen Vincent, MS, RD.

Balanced snacks

These munchies combine protein, fats, and carbohydrates into a well-balanced package.

  • Whole-grain toast topped with nut butter and sliced bananas
  • Hummus and veggies on whole-grain pita bread
  • A handful of nuts and dried fruit
  • Yogurt and nuts or fruit
  • Cheese slices and whole-grain crackers or vegetable sticks
  • A hard-boiled egg and vegetable sticks
  • Tuna, whole-grain crackers, and vegetable sticks
  • Cheese-and-bean quesadilla triangles
  • Cottage cheese and cubed fruit
  • Edamame and whole-grain crackers
  • Turkey, cheese, and veggie wrap

Source: Debra Boutin, MS, RD

Too much protein powder?

Protein mixes, energy bars, and soy milk are all the rage, which means many of us get a lot of supplemental protein in our diets. Soy, in particular, has been praised for lowering cholesterol, but recent studies question its potency — and whether its positive effects result from soy's healthy fats, fiber, and vitamins and minerals, and not actually from its protein content. But no one knows for certain if protein isolated from whole foods (for example, the soy protein isolate found in some energy bars) affects our bodies differently than, say, soybeans or tempeh. Most experts agree, however, that when in doubt it's best to choose high-quality, whole-food proteins over processed ones.

Accounting to amino acids

Animal-based protein sources (meat, fish, dairy, and eggs) are considered “complete” because they contain all nine essential amino acids — those the body can't make and needs to get through food sources.

Plant-based protein sources (grains, legumes, nuts, and seeds) usually are limited in one or more essential amino acids. But vegetarians need not despair. You can easily combine plant protein sources to get all the necessary aminos.