Q. When I bought a rice protein powder recently, the clerk said I’d be better off with the whey protein because it is a “better quality” protein. What does this mean?
A. Increasingly the field of nutrition is becoming more sophisticated. When judging protein quality, it is now necessary to know what benefits to expect from a particular protein. Also it is no longer sufficient to speak of simply the amount of protein in a food. It is now necessary to stipulate the amounts of the various individual amino acids that make up the protein, since different amino acids will be used selectively in the body to accomplish different objectives.
When protein quality is judged by growth of a laboratory animal, the amount and balance of the individual amino acids can be more important than the total amount of protein. This can be illustrated by comparing the nutritive value of eggs to Jell-O. Both have about 10% protein, yet eggs are decidedly more nutritious than Jell-O. There are several other considerations for judging protein quality, such as digestibility, the potential for an allergic reaction, and the presence of uniquely valuable components.
Whey protein has long been favored as a protein supplement by bodybuilders because of, among other things, its low cost compared to many other proteins. As a byproduct of cheese-making, it is abundantly available for about 50 cents a serving. Another advantage it has over other protein supplements is a high content of leucine and other “branch-chain” amino acids. Branch-chain amino acids are incorporated directly into muscle tissue and are the first ones used up during periods of exercise and resistance training. Research has shown that bodybuilders have more lean muscle tissue and less body fat when their diets contain abundant leucine.
Whey is also rich in the amino acid cysteine, which provides an extra boost to the immune system by raising glutathione levels. Glutathione is a powerful antioxidant that controls cancer-causing free radicals and is also used to cleanse the body of many harmful toxins. At the 2003 annual meeting of the American Cancer Society, research was presented showing that, compared to individuals with the lowest levels of cysteine in their blood, women with the highest levels of cysteine lowered their risk of breast cancer by more than 50%.
Whey protein contains many of the same components found in human breast milk and is a key ingredient in a wide variety of infant formulas, including those for premature babies. While breast-feeding is much preferred, baby formulas containing whey protein are the next best thing when breast-feeding is not possible. In addition, whey protein is an excellent protein choice during pregnancy when protein requirements increase by about one-third.
Whey also contains lactoferrin, an iron-binding protein that makes iron more absorbable for babies without causing constipation and in adults reduces the risk of atherosclerosis. Whey-supplemented mice lived about 30% longer than those fed commercial mouse food, and similar results have been obtained with other laboratory animals.
In general, proteins of animal origin are superior to plant-derived proteins. Whey protein, since it is derived from milk, would be superior to rice protein in all but the risk of an allergic reaction.
This article appears in May 7 • 2004.