What exactly is whey protein? Is it good for you? Here a registered dietitian answers all of those questions and more, backed by research.
Each product we feature has been independently selected and reviewed by our editorial team. If you make a purchase using the links included, we may earn commission.

Looking to jazz up your breakfast smoothie or post-workout shake with protein powder but feeling overwhelmed with the plethora of protein powder supplements available? Here we focus on whey protein, one of the most common types of protein powder available. Read on to find out what it is, its benefits and downsides, the different types of whey protein available and how to choose a whey protein powder that best suits your needs.

What Is Whey Protein?

Whey protein is one of the two proteins found in cow's milk. When milk is used to produce cheese, the curding process separates the curds from the liquid, also known as whey. Whey is a nutrient-dense, nearly translucent liquid consisting of all nine essential amino acids (the building blocks of protein) and vitamins and minerals. The liquid whey is filtered and dried to make whey protein powder.

Whey protein powder is often used as a nutritional supplement, and it can be added to smoothies, shakes, protein bars and balls, meal replacements and more. Because whey is dairy-based, it is not a vegan product. You'll want to look for a plant-based protein powder instead, such as soy, hemp, pea or rice, if you are following a vegan diet.

heap of protein powder on a designed background
Credit: Adobe Stock / Volodymyr Shevchuk

Whey Protein Benefits

Here are some of the potential health benefits of whey protein, plus a few potential side effects to watch out for.

Muscle Mass

Protein is vital for gaining muscle mass, and there is a lot of evidence to back this up, including a 2019 study in the Journal of Exercise Nutrition & Biochemistry. Eating enough protein may also help prevent muscle loss due to aging. According to a 2020 review in Experimental Gerontology, whey protein has been shown to be a good protein option for the aging population. From a medical standpoint, whey protein may also be used as a protein source for providing extra nutrition to people who have illnesses and need to gain body weight, as well as for healing wounds after an injury or surgery, according to a 2020 review in Nutrients.

Generally speaking, you want to try to get enough protein from the foods you eat in meals and snacks, including both animal and plant-based proteins, such as meat, poultry, fish, eggs, tofu and legumes. However, from amateurs to professional elites, physically active people may try whey protein to improve their athletic performance and gain muscle strength and mass. In this situation, whey protein is extra protein added to their existing diet.

Whey protein may also be preferred over other types of protein powder, such as casein protein, because whey protein is more easily digested and absorbs faster than casein protein, per the 2020 Nutrients review.

Blood Sugars

Studies have noted that whey protein might be helpful in regulating blood sugar levels, including the 2021 study published in the Journal of Nutritional Science. And in a small 2022 study in BMJ Open Diabetes Research & Care, participants with Type 2 diabetes who ingested 100 milliliters of a supplement that contained about 15 grams of whey protein 10 minutes prior to eating had a reduced risk of high blood sugars (hyperglycemia) after eating and were more likely to have blood sugar levels in desired ranges throughout the day (euglycemia).

Weight Loss

Another potential benefit of whey protein is weight loss. We know the beneficial effects protein can have on increasing satiety and making weight loss easier. And studies show that whey protein, in particular, can be effective. For example, in a 2022 meta-analysis in Clinical Nutrition ESPEN, researchers determined that whey protein intake is associated with a positive change in body composition, in particular, a reduction in body fat. According to this review, the greatest benefits were evident when the whey protein was accompanied by a reduction in total calorie consumption and the inclusion of resistance training.

Whey Protein Side Effects

Some people may have unpleasant symptoms, such as headache, nausea and cramps when consuming whey protein in large doses. Individuals who are allergic to or intolerant of milk protein may also experience adverse reactions if they consume whey protein since it is a milk-derived ingredient.

A 2020 review in Applied Physiology, Nutrition and Metabolism provides a few more warnings of whey protein when used in excess, including an exacerbation of acne, negatively modifying the gut microbiome and even liver and kidney damage. It's important to follow the directions on the whey protein supplement label and avoid taking more than the recommended amount.

Types of Whey Protein: What's the Difference?

You may have come across different types of whey protein, but how do you differentiate one from the other? For instance, what is whey protein isolate versus whey protein concentrate?

Simply put, whey protein concentrate (WPC) has a higher concentration of fat and carbohydrate than its counterpart, whey protein isolate. The amount of protein present in WPC can vary between 30% and 80%, per the USDA.

Whey protein isolate (WPI), on the other hand, has more fat and carbohydrate filtered out, leaving a protein concentration of at least 90%; basically, the manufacturer has isolated the whey protein, providing a product with a higher concentration of whey protein. WPI also tends to be pricier than WPC because further processing is needed.

Whey protein hydrolysate (WPH) is another term for hydrolyzed whey. WPH is the pre-digested or broken-down form of whey protein, allowing for easier absorption. Among the three types of whey protein, this form of whey protein is the easiest to digest. It is also commonly used in specialized infant formulas and medicinal protein supplements.

Whey protein concentrate and whey protein isolate are the most common forms of whey protein available for sale. However, which one you would pick will depend on your budget, needs and goals. For example, suppose you are lactose intolerant. In that case, you might want to choose the whey protein isolate because more lactose, a type of sugar (also a carbohydrate) found in milk and dairy products, is removed during the filtration process.

How to Choose a Whey Protein Powder

In addition to choosing the type of whey protein that fits your needs, other ingredients in the product are also key factors to consider.

Read the Ingredients List

Whey protein powder in its natural form may not be appealing to everyone's palate, so manufacturers may add sugar and flavorings to enhance its taste. Look for a protein powder that lists whey protein as the only ingredient—you can add just the right amount of sweetness if desired—or choose one that is low in added sugars, sweeteners, additives and fillers.

Choose a Product Tested by a Third Party

Dietary supplements like whey protein are currently not regulated by the FDA to the extent that food products are. Under federal law, the manufacturer can make claims about a product without requiring FDA approval before selling it to the public.

To ensure what you buy is what you are really getting—and is safe—look for a protein powder that has been approved and certified by a third-party organization, such as the NSF or Informed Choice. By looking for the seal of approval, you can rest assured that the product has been tested, analyzed and verified by an organization independent from the manufacturer. Specifically, the verification looks at the product's ingredients, such as the quantity of protein included, and whether any heavy metals, such as lead and arsenic, are present.

What Is the Best Whey Protein Powder?

The best type of protein powder for you depends on your needs. But, looking at the ingredient lists and verification from third-party organizations, these two brands are good options.

Naked Grass Fed Unflavored Whey Protein Powder (5 lbs.)
($109.99 save 14%)
shop it
Pure Whey Protein Powder Vanilla (2 lb. bag)
shop it

The Bottom Line

Ultimately, your question is: Do I need whey protein? As mentioned earlier, you should meet your protein needs without needing protein supplements if you're eating a nutrient-dense diet. However, you may want to include protein powders as part of your lifestyle for different reasons.

Some people may take protein powders to improve their endurance and strength as they build and maintain their muscles. Others may add protein powder to their diet for top-up purposes if they are having trouble eating enough protein foods. And some individuals may use it due to swallowing and chewing problems, as it's easier to ingest protein powder mixed with food and beverages to meet their nutritional requirements.

Whether or not you need that extra protein will depend on your nutritional needs and goals, so it's best to speak with a registered dietitian to determine your protein needs before purchasing. If you do decide to invest in a protein powder, look for products from reputable brands with third-party approvals, read the ingredients lists and follow the instructions provided to avoid using it in excess due to the potential negative side effects of doing so.