What is whey protein and should you be taking it? Safety, benefits and what to know

Few industries are doing as well as the dietary supplement one. The global size of the market reached 71.81 billion in 2021 and is projected to grow by tens of millions more to a whopping 128.64 billion by the year 2028.

While supplemental nutrients such as vitamin D, vitamin C, vitamin B12, magnesium and calcium are the most widely taken, many others including ginseng, coconut oil, ashwagandha and creatine have also risen considerably in popularity over the past decade. There's no denying, the interest in these products is high. But among such supplements, few are promoted as frequently or as fervently as whey protein.

What is whey protein?

Whey protein is a popular protein supplement marketed as being able to improve one's athletic performance and build stronger, leaner muscles. It's usually taken pre- or post-workout and is consumed as a powder (often diluted in a smoothie or cup of water/milk) and is also sold as part of a ready-to-drink protein shake.

The protein comes from whey − the watery portion of milk that is separated from the curds when making cheese. "Cow's milk consists mainly of two proteins: casein and whey," says Uma Naidoo, MD, director of nutritional and lifestyle psychiatry at Massachusetts General Hospital and the author of “This is Your Brain on Food." She explains that the whey portion of the protein is thought to be "a complete protein as it contains all nine essential amino acids."

The nine amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Per the National Institute of Health's National Library of Medicine, these amino acids carry out vital body functions including the absorption of nutrients and tissue repair and must be obtained through a healthy diet or supplementation.

Carol Johnston, PhD, RD, a professor of nutrition at Arizona State University, says that consuming whey protein is one way "to increase dietary protein intake," and that the "amino acid profile of whey protein allows for maximal protein synthesis."

What does whey protein do to the body?

Whey protein is marketed as having several health benefits, but research showing the full extent of each benefit (or lack thereof) is still ongoing. "Whey protein supplementation has been found to help support athletic performance in a literature review," explains Naidoo.

Whey protein is also promoted for being helpful with diabetes, immune health, asthma, and weight loss, though robust science doesn't yet back up such claims. At the very least, "whey protein is a highly bioavailable source of animal protein that is absorbed quickly after ingestion," says Johnston. Protein has been shown to target muscle growth and development, strengthen bones, and help with cell growth and repair.

Is whey protein powder safe to take?

Despite some of whey protein's health benefits, it's classified as a dietary supplement − meaning it isn't regulated by the U.S. Food and Drug Administration (FDA) the way drugs are. Indeed, Harvard Medical School warns of some "hidden dangers" in protein powders, including high amounts of sugar and calories, the presence of unknown substances, and even toxins that have been discovered in some protein powder brands.

Still, whey protein isn't known to cause harm in most adults when taken in moderate amounts, especially in the protein-deficient or those needing more such as athletes, the elderly or vegetarians. Naidoo says for some such people, whey protein is an "option worth considering to supplement your protein intake," but adds that such supplementation ought to be temporary (unless directed by a physician) and shouldn't take the place of a healthy diet. "A systematic review of both experimental and randomized research studies looked at whey protein and the effect on physical health and showed that ongoing long-term use without the help of a medical or nutrition professional can cause side effects on the kidney and liver," she explains.

In other words, the best and safest way to ensure one gets enough protein is to get it from natural sources the way many do from their everyday diet. "Individuals consuming a healthy diet including all food groups are likely ingesting adequate amounts of protein," says Johnston.

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This article originally appeared on USA TODAY: What is whey protein and is it good for you? Benefits, what to know