Not all types of protein are created equal. The body uses protein from different foods in different ways. The higher its biological value [BV]—i.e., the percentage absorbed by the body—the more complete the protein.
Below, we break down several different types of protein, including how they are digested and absorbed by your muscles.
Types of Protein
Animal proteins—including eggs, egg whites and milk—have the highest BV, because they contain all of the amino acids needed for muscle growth. When choosing an animal protein, aim for lean sources, like fish or chicken. Use the motto: "the fewer legs the better."
The Scoop: Your body absorbs animal proteins best. Try to include one lean protein source with each meal or snack—or at least twice a day.
Probably the most generic protein supplement, whey is a simple byproduct of milk, containing about 20 percent of its proteins. When dairy products such as cheese are manufactured, the whey separates from the casein [learn about casein below]. Whey is lactose-free; and since it contains many branched-chain amino acids [BCAAs], it is considered a high-quality, complete protein, delivering all the nutrients required to help muscles recover. Furthermore, it is easily digestible, promoting rapid absorption by the major muscle groups. [Read more about whey protein.]
The Scoop: Its fast-acting properties make whey protein an ideal choice to consume within 30 minutes after a workout.
Casein is the other protein derived from milk, carrying about 80 percent of its protein content. The major difference between casein and whey is that casein is digested at a slower rate, which makes it less ideal for consumption immediately after working out. Casein thickens and clots slightly in the stomach, which allows it to be sustained in liquid form but reduces the speed at which it is absorbed into the bloodstream. The amino acids in casein are released gradually and evenly, reaching peak levels—and protein synthesis—within three to four hours. Hence, the best time to consume casein protein is late evening or before bed, experts say.
The Scoop: Consume casein when your body has time to digest and absorb the protein. Cottage cheese is a great source of this type of protein.
Soy protein—derived from soy beans—is a highly-debated protein. Although it has been associated with a variety of health benefits—including decreased risk for cancer—some studies have linked it to reduced testosterone levels in men, possibly due to its estrogen-like compounds, called isoflavones. In a 2005 study comparing soy to casein, the Journal of Nutrition claimed that "the biological value of soy protein must be considered inferior," resulting in less protein synthesis in the body.
Nevertheless, soy is fairly common in many sports nutrition products. It is economical, low in fat and cholesterol, high in antioxidants and BCAAs, and is the only complete vegetable protein. Its digestion rate is moderate, so it can serve as a "bridge" between whey's and casein's supply of amino acids. For athletes who are allergic to whey or are vegetarian, soy is the prime alternative.
The Scoop: Consume mainly other proteins, but including one or two servings a day—e.g., in half cup of tofu or edamame, a cup of soy milk or an ounce of soy nuts—can be beneficial to your health, recovery and athletic performance.
Other Vegetable Proteins
These include nuts and seeds, beans and whole grains—all important to include in your diet, especially in combination with another source to create a complete protein. For example, combine beans with grains or vegetables with eggs to get all the amino acids you need. [Read more on vegetarian protein.]
To learn more, check out these other protein-related articles:
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