How Much Protein Do You Need in Your Diet?
A normal American diet generally provides sufficient protein, so protein deficiencies are rare in the United States. The National Academy of Sciences Food and Nutrition Board sets requirements (RDAs) for nutrients such as vitamins and minerals and for daily dietary protein consumption. As with other nutrients, the board has different recommendations for different groups of people: younger or older, men or women.
As you age, you synthesize new proteins less efficiently, so your muscle mass diminishes while your fat content stays the same or rises. This is why some folks believe that muscle turns to fat in old age.
As a general rule, the National Academy of Sciences says healthy people need to get 10 to 35 percent of their daily calories from protein. More specifically, the Academy has set a Dietary Reference Intake (DRI) of 45 grams protein per day for a healthy woman and 52 grams per day for a healthy man.
These amounts are easily obtained from two to three 3-ounce servings of lean meat, fish, or poultry (21 grams each). Vegetarians can get their protein from 2 eggs (12–16 grams), 2 slices of prepacked fat-free cheese (10 grams), 4 slices of bread (3 grams each), and one cup of yogurt (10 grams).
Protein deficiencies result in weak muscles. For example, children who do not get enough protein have shrunken, weak muscles. They may also have thin hair, their skin may be covered with sores, and blood tests may show that the level of albumin in their blood is below normal.
Protein is needed to produce new red blood cells, which live for only 120 days. People who do not get enough protein may become anemic. Protein deficiencies may also show up as fluid retention (the big belly on a starving child), hair loss, and muscle wasting caused by the body digesting the proteins in its own muscle tissue. That’s why victims of starvation are, literally, skin and bones.
Anyone who’s building new tissue quickly needs extra protein. For example, the Dietary Reference Intake (DRI) for protein for women who are pregnant or nursing is 71 grams per day. Injuries also raise your protein requirements. An injured body releases protein-destroying hormones from the pituitary and adrenal glands.
You need extra protein to protect existing tissues, and after severe blood loss, you need extra protein to make new hemoglobin for red blood cells. Cuts, burns, or surgical procedures mean that you need extra protein to make new skin and muscle cells. Fractures mean extra protein is needed to make new bone.
Recent research suggests that athletes need extra protein, but they easily meet their requirements by increasing the amount of food in their normal diet.
You can get too much protein. Several medical conditions make it difficult for people to digest and process proteins properly. As a result, waste products build up in different parts of the body.
People with liver or kidney disease don’t process protein efficiently into urea or don’t excrete it efficiently through urine. The result may be uric acid kidney stones or uremic poisoning. The pain associated with gout is caused by uric acid crystals collecting in the spaces around joints. Doctors may recommend a low-protein diet as part of the treatment in these situations.