What is whey protein as a dietary supplement?

Overview

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.

Sources

When milk is converted into cheese, whey is the liquid that is left behind. There is no specific dietary requirement for whey, because the amino acids it contains are present in a wide variety of other foods too.

Therapeutic Doses

A typical dose of whey protein is 20 to 30 grams per day.

Therapeutic Uses

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, human immunodeficiency
virus (HIV) infection, liver disease, diabetes, and various types of cancer. 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 when it is taken by
mouth. 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 infection. However, while these are promising findings, one essential piece
of evidence is lacking: There is no evidence 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. 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. However, a single small study did find ergogenic benefits with whey compared with casein.

One study looked at whether whey protein could help women with HIV build muscle mass. Study 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 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, the use of alpha-lactalbumin in the evening improved morning alertness, perhaps by enhancing sleep quality. Another small double-blind study found weak evidence that alpha-lactalbumin improved mental function in people sensitive to stress. A third study failed to find that alpha-lactalbumin significantly improved memory in women experiencing premenstrual symptoms.

Weak evidence hints that whey might help prevent cancer or augment the effectiveness of cancer treatment. Infant formula based on predigested (hydrolyzed) whey protein is somewhat less allergenic than standard infant formula; this might reduce symptoms of colic and possibly decrease the risk that the infant will later develop allergies.

Safety Issues

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 (even to partially hydrolyzed forms of whey).

Bibliography

Agin, D., et al. “Effects of Whey Protein and Resistance Exercise on Body Cell Mass, Muscle Strength, and Quality of Life in Women with Human Immunodeficiency Virus” AIDS 15 (2001): 2431-2440.

Borsheim, E., et al. “Effect of an Amino Acid, Protein, and Carbohydrate Mixture on Net Muscle Protein Balance After Resistance Exercise.” International Journal of Sport Nutrition and Exercise Metabolism 14 (2004): 255-271.

Chromiak, J. A., et al. “Effect of a Ten-Week Strength Training Program and Recovery Drink on Body Composition, Muscular Strength and Endurance, and Anaerobic Power and Capacity.” Nutrition 20 (2004): 420-427.

Markus, C. R., et al. “Evening Intake of Alpha-Lactalbumin Increases Plasma Tryptophan Availability and Improves Morning Alertness and Brain Measures of Attention.” American Journal of Clinical Nutrition 81 (2005): 1026-1033.

Marshall, K. “Therapeutic Applications of Whey Protein.” Alternative Medicine Review 9 (2004): 136-156.

Micke, P., et al. “Effects of Long-Term Supplementation with Whey Proteins on Plasma Glutathione Levels of HIV-Infected Patients.” European Journal of Nutrition 41 (2002): 12-18.

Szajewska, H., et al. “Extensively and Partially Hydrolysed Preterm Formulas in the Prevention of Allergic Diseases in Preterm Infants.” Acta Paediatrica 93 (2004): 1159-1165.