Whey is one of the two major classes of protein in milk. (The other is casein, the “curds” of “curds and whey.”) Proteins are made of amino acids, and whey contains high levels of the amino acid cysteine. This is the basis for many of its proposed uses. It also contains branched chain amino acids ( BCAAs ). However, while there is no question that whey is a highly digestible and rich protein source, there is no meaningful supporting evidence that it provides any specific health benefits.
When milk is converted into cheese, whey is the liquid that is left behind. There is no specific dietary requirement for whey, as the amino acids it contains are present in a wide variety of other foods, as well.
There are no well-documented medicinal uses of whey protein.
There is some evidence that whey can raise levels of glutathione . Glutathione is an antioxidant that the body manufactures to defend itself against free radicals. In certain diseases, glutathione levels may fall to below-normal levels. These conditions include cataracts , HIV , liver disease, diabetes , and various types of cancer. 1 This reduction of glutathione might in turn contribute to the symptoms or progression of the disease. To solve this problem, glutathione supplements have been recommended, but glutathione is essentially not absorbed at all when it is taken by mouth. 2 Whey protein may be a better solution. The body uses cysteine to make glutathione, and whey is rich in cysteine. Meaningful preliminary evidence suggests that whey can raise glutathione levels in people with cancer, hepatitis , or HIV . 3-8
However, while these are promising findings, one essential piece of evidence is lacking: there is no evidence as yet that this rise in glutathione produces any meaningful health benefits.
Whey protein has also been proposed as a bodybuilding aid , based partly on its high content of BCAAs . However, there is no more than minimal evidence that whey protein helps accelerate muscle mass development. 9-11 Furthermore, there is little evidence that whey protein is more effective for this purpose than any other protein. For example, one small double-blind study found evidence that both casein and whey protein were more effective than placebo at promoting muscle growth after exercise, but whey was no more effective than the far less expensive casein. 12 However, a single small study did find ergogenic benefits with whey as compared to casein. 32
One study looked at whether whey protein could help women with HIV build muscle mass . 13 Participants were divided into three groups: those who undertook a course of resistance exercise (weight lifting), those who took whey, and those who did both. Resistance exercise alone was just as effective as resistance exercise plus whey, while whey alone was not effective.
Whey contains alpha-lactalbumin, a protein that in turn contains high levels of the amino acid tryptophan. Tryptophan is the body’s precursor to serotonin, and is thought to affect mental function. In a small double-blind study, use of alpha-lactalbumin in the evening improved morning alertness , perhaps by enhancing sleep quality. 14 Another small double-blind study found weak evidence that alpha-lactalbumin improved mental function in people sensitive to stress. 15 A third study failed to find that alpha-lactalbumin significantly improved memory in women experiencing premenstrual symptoms . 16
Very weak evidence hints that whey might help prevent cancer or augment the effectiveness of cancer treatment . 17-27
Infant formula based on pre-digested (hydrolyzed) whey protein is somewhat less allergenic than standard infant formula; this might reduce symptoms of colic28 and possibly decrease the risk that the infant will later develop allergies. 29,30
As a constituent of milk, whey protein is presumed to be a safe substance. People with allergies to milk, however, are likely to be allergic to whey as well (even partially hydrolyzed forms of whey). 31
References
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29. Chandra RK. Five-year follow-up of high-risk infants with family history of allergy who were exclusively breast-fed or fed partial whey hydrolysate, soy, and conventional cow's milk formulas. J Pediatr Gastroenterol Nutr . 1997;24:380-388.
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Last reviewed April 2009 by EBSCO CAM Review Board
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