Whey Protein: Health Benefits and Potential Side Effects

Little Miss Muffet may have been well ahead of her time. She was eating curds and whey before whey protein was a thing. Today, whey protein is an ingredient in many nutritional bars and shakes.

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Registered dietitian Maxine Smith, RD, LD, explains the pros and cons of whey protein and whether you need this supplement in your life.

What is whey protein?

Whey protein refers to a group of eight proteins found in milk. These proteins, in order from the biggest to smallest amounts in milk, are:

  • Beta-lactoglobulin.
  • Alpha-lactalbumin.
  • Glycomacropeptide.
  • Immunoglobulins.
  • Bovine serum albumin.
  • Lactoferrin.
  • Lactoperoxidase.
  • Lysozyme.

Manufacturers add enzymes to milk in the cheese-making process. The enzymes curdle the milk, which separates the liquid whey from milk’s solid curds. The curds, which contain most of the milk’s fat, are the main ingredient in cheese.

When the solid curds are removed, you’re left with watery whey protein, which has varying amounts of lactose (milk sugar) and fat. Usually, manufacturers pasteurize the whey to kill bacteria and then dry it. Voila! Whey protein powder.

Types of whey protein

Whey protein then undergoes another process to make one of three main types:

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  1. Concentrate: Products with whey protein concentrate vary widely in their protein, lactose and fat content. Whey protein concentrate is in many protein drinks, bars and nutritional products. It’s also used in infant formula.
  2. Isolate: This type is consistently high in protein and low in fat or lactose. You may see it listed on the labels of protein supplements, such as bars and drinks. Whey protein isolate may be a suitable choice for people who are lactose intolerant — but don’t try any of these if you have a milk allergy.
  3. Hydrolysate: Also known as hydrolyzed whey protein, whey hydrolysate is the easiest to digest. It’s gentle on digestion because its long protein chains, called peptides, are pre-broken down into shorter ones. Specialized infant formulas often use hydrolyzed whey protein. You may also see it in medical supplements for nutritional deficiencies.

Amino acids and whey protein

Whey protein is a complete protein, containing all nine essential amino acids. “Amino acids are important for many functions in the body, from building muscle to creating new immune cells,” says Smith.

Your body makes many amino acids on its own, but not essential amino acids. You have to get essential amino acids through your diet, and consuming whey protein is one way to do that.

But don’t discount “incomplete” proteins. Most plant proteins, like legumes and nuts, don’t contain all the essential amino acids. But they have plenty of health benefits. When you eat a variety of incomplete proteins, you get more than enough essential amino acids to meet your body’s needs.

Benefits of whey protein

Whey protein may be useful for:

  • Muscle building: Muscles love protein, especially complete proteins like whey. “Whey protein contains branched-chain amino acids, a specific type of amino acid that helps with muscle building,” Smith says.
  • Wound healing: The amino acids in whey protein help repair skin and tissues from wounds or surgery.
  • Weight gain and nutritional boost: People who need to gain weight can benefit from whey protein. It’s also helpful if a person has a long-term illness and needs extra nutrition. “If you can’t get enough protein from whole food sources, a whey protein supplement can help,” says Smith. “It’s beneficial for people who have chewing or swallowing disorders or a lack of appetite.”

Side effects and risks of whey protein

Whey protein is generally safe for most people to take, as long as they don’t have a dairy allergy. But there are some drawbacks:

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  • Calorie content: Whey protein may be low fat and low carb, but it still has calories. “Too many calories from anything, including protein, leads to weight gain,” Smith explains.
  • Extra sugar or processed ingredients: Many protein powders and shakes contain processed ingredients like artificial flavors, sweeteners or added sugar. “It’s better to get your protein from whole foods and a varied diet, rather than a supplement, bar or shake,” says Smith. “If you use a supplement, look for one that lists whey protein as the only ingredient.”
  • Possible contaminants: Protein supplements don’t have strict regulations like foods and drugs. “The purity might not be proven in some protein supplements,” says Smith. “They can have fillers or heavy metal contaminants that aren’t listed on the label.” Choose whey protein products that are NSF Certified for Sport or certified by Informed Choice. These products have been independently tested for purity.
  • Possible digestive problems: Some people experience constipation, diarrhea or nausea from taking whey protein, especially if they take large amounts.

Don’t go overboard with protein

Whey protein has its place if you’re an athlete building muscle or trying to fill some nutritional gaps. But most people already get enough protein and don’t need supplements.

“Your body can only use 20 to 40 grams of protein at a time,” Smith says. “Even if you’re trying to bulk up, taking amounts higher than this isn’t helpful. Most people don’t need whey protein to meet their protein requirements if they’re eating a healthy diet.”

As with any supplement, it’s best to discuss with your physician before you start taking protein supplements. They can interfere with some medications or may actually be harmful for people with certain conditions.


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