How Much Protein Is Good for You?

Proteins are the building blocks of muscles and are essential for healthy immune, circulatory and respiratory systems. Too little can lead to malnutrition and death, but too much can cause problems as well. Complicating the issue is the fact that not all protein is the same. Amino acids, the molecules that make up protein, come in 20 different varieties, some that are made by the body and some that must be consumed in the diet. The combination of different amino acids is as important as the total amount of protein consumed.

Lean Body Mass

• One way to estimate how much protein is good for you is based on lean body mass. To calculate your lean body mass, multiply your weight by your percentage body fat. A woman who weighs 140 pounds and has 10 percent body fat has a lean body mass of 126 pounds (140 -- 14 = 126). A normal adult thrives on anywhere between 0.4 to 0.8 grams of protein per pound of lean body mass per day. This means our 140-pound woman should be getting between 50 and 100 grams of protein from her diet every day. This wide range narrows depending on the age, activity level and lifestyle of the individual. A woman will need more protein when she is lactating or exercising regularly than if she leads a sedentary lifestyle.

Physical Activity

• Of course, an individual's level of physical activity will also influence their nutritional needs. Bodybuilders and those who frequently engage in strenuous physical activity can eat as much as 1 to 1.5 grams of protein per pound of lean body mass. A man who weighs 160 pounds, has 5 percent body fat, and exercises at least three times a week and is trying to build muscle will need more protein than the woman in the previous example. With a lean body mass of 152 pounds and his strenuous weight training, he can eat 150 to 230 grams of protein per day.

Total Calories

• A different way to think about protein intake is the percent of total caloric intake. Protein makes up about 15 percent of body weight, and it's believed it should make up about the same percent of total calories. For an individual on a 1,500-calorie diet, this is 225 calories from protein. Since 1 gram of protein has 4 calories, this is a total intake of about 56 grams per day. As with the body mass method, this rule of thumb can be flexible. A bodybuilder might eat as much as 21 percent of their calories in protein, whereas someone else might eat as few as 10 or 12 percent.

Protein Sources

• Nutritionists almost universally recommend obtaining protein from a wide variety of sources, both plant and animal. Animal sources provide the complete proteins, meaning they contain all the essential amino acids. Unfortunately, except for in very lean meats like chicken or fish, most of the calories in animal-based foods come from fat and can promote heart disease and weight gain. Vegetable proteins are low in saturated fats but are usually incomplete proteins (a few grains such as quinoa are complete proteins), which means they must be eaten in combination with others. A classic example is beans and rice, which together provide a complete protein.

Too Much Protein

• Protein metabolization, especially from animal sources, creates byproducts that strain the liver and kidneys. Too much protein in the diet for a prolonged period can have a seriously negative impact on these organs. It's also dehydrating because of the large amounts of water needed for protein digestion and muscle synthesis. Gout is a disease that has been specifically linked to the over-consumption of animal proteins. There is some controversy over whether the risks of high-protein intake are exacerbated by low-carbohydrate diets, but the consensus is that ketogenic diets, which consist entirely of protein and fat, should not be sustained for the long term.