Test Your Knowledge

Consuming protein beyond amounts the body requires (e.g., 46 to 56 grams per day for most adults) provides no additional health benefits. Any excess protein in the diet is removed from the body through urine and stool or is converted into fat. Eating more protein will not increase muscle development.

Excessive amounts of protein have been associated with a number of health problems, including:

• Heart disease. Homocysteine is produced during the processing of the amino acid methionine. Homocysteine may play a role in the development of atherosclerosis, the narrowing of blood vessels that is a major risk factor for heart disease, heart attack and stroke. Furthermore, many protein sources are also high in fats, especially saturated fats. This can also increase the risk of developing atherosclerosis.
  

  

• Osteoporosis. The body’s breakdown of proteins may release potentially harmful byproducts, and the body uses calcium and other substances to neutralize these byproducts. However, calcium used for this purpose is no longer available to increase bone density. In addition, if there is not enough calcium in the diet, the mineral may be pulled directly from the bone during protein digestion. This weakens the bone and increases the risk of osteoporosis.

Protein may need to be restricted in patients with certain medical conditions, such as liver or kidney disease. Processing large amounts of proteins and amino acids can become stressful for a diseased liver or kidneys. If these organs do not efficiently process these substances, a byproduct called urea may build up in the kidneys, blood or elsewhere. This can lead to kidney stones, uremic poisoning and possibly gout. Because of this, patients with liver or kidney disease often need to limit their intake of protein. A physician and dietitian can suggest ways to get adequate protein without stressing an impaired liver or kidneys.

Recent studies have also linked excessively high protein consumption to a greater risk of developing certain types of cancer.

Some popular diets recommend consumption of high amounts of protein and low amounts of carbohydrates. Studies have shown that these diets may provide greater immediate weight loss than diets low in fat and high in carbohydrates. For example, one recent study found that consuming higher levels of dietary protein may trigger production of a hormone called peptide YY. People will higher levels of this hormone may feel more full, causing them to eat less and to lose weight.

However, other studies have found that many people who initially lose weight on high-protein diets eventually gain back the pounds. Highly restrictive diets like these may be difficult for many people to maintain, resulting in a rebound of weight after the diet has been deserted.

In addition to the health concerns regarding high protein intake, there are also concerns regarding a low intake of carbohydrates, especially since many important nutrients come from carbohydrate-rich foods.