Whey protein is a perfect protein supplement for athletes, strength and high-intensity trainers, and even those struggling with obesity or type 2 diabetes. It helps build muscle and prevents muscle wasting while burning through stubborn belly fat. When combined with exercise, whey protein is an excellent tool to boost both muscle gain and weight loss. Read on to discover the health benefits and side effects of whey.

What is Whey Protein?

Whey protein is a mixture of proteins found in the commonly discarded liquid portion produced during the cheese manufacturing process. It is found in the milk of nearly all animals, including humans.

Whey protein is rich in vitamins, minerals, and essential amino acids needed for muscle growth. Along with many other minor proteins, ⍺-lactalbumin and β-lactalbumin are the two major proteins found in whey [1].

Casein is the most abundant protein in milk, while whey protein accounts for roughly 20%.

How Does Whey Protein Work?

Whey protein is a high-quality protein supplement providing large amounts of rapidly and easily digestible amino acids. Whey protein promotes greater growth of muscle due to the availability of these amino acids, which are the muscle’s building blocks [2].

Muscle growth can only be achieved if the rate of muscle building is greater than the breakdown of muscle protein [3].

Whey Protein Types

Isolate (WPI)

This isolated form of whey protein is the most concentrated form of whey protein (90 – 95%) while containing little lactose and fat. WPI is great for those with lactose-intolerance but usually, comes at a higher price [4].

Concentrate (WPC)

Whey protein concentrate is popular among athletes due to its large range of protein content (25 89%), lots of fat, and biologically-active components [4, 5].


Hydrolyzed whey protein is produced when hot acid and/or enzymes break down whey proteins into smaller more quickly and easily digestible protein. This predigested protein may enhance muscle protein synthesis [6].

Health Benefits of Whey Protein

1) Helps Muscle Gain and Weight Loss

Strength and muscle mass decline with age [7].

During a caloric restriction diet, the body uses existing protein for fuel. Whey protein supplements give the body the amino acids needed to maintain muscle mass during this type of diet.

In a study of 19 men and 21 women assigned to either a whey protein supplement, a soy-based supplement, or a carbohydrate supplement throughout a weight loss regimen. Those using whey protein supplementation preserved more lean muscle mass while losing weight [8].

The amino acid leucine is the driving factor for muscle growth in whey protein. Rats taking leucine supplements experience the same effect on muscle protein synthesis as whey protein [9].

Leucine makes up 12% of the amino acids in whey protein and functions by stimulating muscle growth in the body [10].

Exercises such as cardio, strength training, and quick high-intensity interval exercise significantly decrease leucine levels in the body (up to 30%). Consuming leucine in the form of whey protein before or during intensive exercise prevents degradation of muscle proteins [11].

The amino acids in whey protein also increase lean muscle growth after exercise [3].

2) Helps Fat Loss During Calorie-Reduced Diets

A 12-week study showed that people on a 500-calorie reduced diet lost more body fat and preserved more lean muscle when taking a whey protein fraction high in leucine. Subjects lost 6.1% body fat, which reduces the risk of high body fat-related diseases [12].

3) Improves Digestive System Health

Whey protein is prebiotic that helps good bacteria in the gut and can improve intestinal disorders [13].

Lactoferrin, a protein found in whey, plays an important role in the uptake of iron through the digestive system. Iron is important for carrying oxygen in red blood cells and preventing anemia [14, 15].

While lactoferrin may have other health benefits such as its anti-cancer properties, it may be in too low of quantities in whey to exert these effects [16].

4) Helps Reduce Hunger and Lose Weight

High protein diets improve satiety after a meal by increasing amino acid concentrations in the blood [17, 18].

Whey protein shows the strongest reduction in hunger when compared to other protein supplements such as casein and soy proteins, which is likely caused by the larger levels of leucine in whey protein [19].

Taking whey protein 90 minutes before a meal increases hormones responsible for satiety (CCK and GLP-1), even during a state of reduced caloric intake. The body will reach a satisfying state sooner and with less food [20].

Also, obese patients experienced a significant decrease in liver fat 4 weeks after adding whey protein to their diet [21].

5) Helps Treat Type 2 Diabetes

In type 2 diabetic subjects, whey protein taken during a meal increased the insulin response and significantly decreased blood glucose levels [22].

Those struggling with maintaining a low sugar level in the blood can consume whey protein before a high carbohydrate meal to reduce glucose levels after the meal [23, 24].

6) Increases Antioxidant Defenses

Whey protein contains a large supply of the amino acid cysteine, which is known to be a precursor of glutathione, a powerful antioxidant made by the body [25].

Glutathione is responsible for many health benefits, like restoring cellular damage and preventing diseases such as cancer [26, 25].

7) Is Anti-Cancer

Dietary milk products may have an inhibitory effect on the development of many tumors.

Rat models show that glutathione deficiency is closely related to many types of cancers. Cancer cells with increased levels of glutathione resist cancer therapy, which tries to induce cancer cell death [27].

Whey protein increases glutathione synthesis in normal cells while decreasing glutathione levels in cancer cells. Using whey protein concentrate might become a promising strategy in tackling resistance to cancer therapies [28, 27].

8) Can Naturally Lower Blood Pressure

Fermented dairy products reduce blood pressure in patients with high blood pressure (hypertension) [29].

In fact, fermented milk supplemented with whey protein concentrate lowered blood pressure and cholesterol levels in both mice and healthy men [30].

Whey protein contains a natural bioactive peptide called lactokine, which helps in the treatment of high blood pressure and improves cardiovascular health. Common high blood pressure pharmaceutical drugs contain a synthetic, but more powerful, replacement for lactokine [31].

Six weeks of whey protein supplementation can decrease blood pressure in overweight individuals [32].

9) May Treat Inflammation

Inflammation is the body’s natural reply to tissue damage and pathogens. The immune system clears out injured cells triggering tissue repair. The liver produces C-reactive protein (CRP) in response to inflammation [33].

A meta-analysis revealed high doses of whey protein may reduce CRP levels [34].

A study of elderly patients (65-90 years old) showed that whey protein also reduced inflammation [35].

IBD, like Crohn’s disease or ulcerative colitis, involves chronic inflammation in the digestive tract. Whey protein reduces gut inflammation and damage to the intestinal lining by increasing both antioxidant defenses and good bacteria [36, 37, 37, 38].

10) May Help Reduce High Cholesterol in Overweight Individuals

Low-density lipoprotein cholesterol (LDL-cholesterol) or “bad” cholesterol is a major risk factor for heart disease, heart attack, and stroke [39].

Overweight patients taking high doses of whey protein supplements saw a significant decrease in bad cholesterol [32].

However, a meta-analysis only showed an overall reduction on blood triacylglycerol with no effect on LDL-cholesterol [40].

11) Improves Bone Health in Women

In postmenopausal osteoporosis, bones become fragile from increased bone degradation (resorption) due to hormonal changes (lower estrogen) [41].

Mice mimicking a postmenopausal state with decreased estrogen levels and increased bone resorption had reduced bone loss with whey protein concentrate supplementation [42].

Side Effects

1) Kidney Stone Formation

Too much protein in the diet puts a large amino acid load to the kidneys, increasing the risk of kidney stone formation [43].

Resistance training may counter damage to kidneys caused by a high protein diet [44].

2) Damage to the Kidneys

The acid-base balance in the body is disrupted due to the increased acidity from a high protein diet. Acidic blood damages the kidneys. Fruits and vegetables may prevent this side effect and should be incorporated into a high protein diet [45, 46].

3) Digestive Discomfort due to Lactose Intolerance

Whey protein does contain lactose (a sugar found in milk) and those with lactose intolerance may experience cramping and diarrhea [47].

Whey protein concentrate and whey protein isolate contain small amounts of lactose [4].

3) Acne Breakouts

Insulin-like growth factor-1 (IGF-1) contained in whey protein increases sebum production, which is linked to acne breakouts [48].

Whey protein spikes insulin causing an increase in skin cells, skin inflammation, and oil production resulting in increased acne formation [49, 50].

4) Can Worsen Gout

Gout is a form of arthritis where a metabolic defect in uric acid causes episodes of acute pain, tenderness, and redness. There is no evidence that consuming whey protein can cause gout, but it can worsen this condition.

Whey protein does contain small amounts of purine, a protein responsible for making uric acid. Foods containing purine increase the risk of recurrent gout attacks [51].

Evidence suggests that anti-inflammatory properties and low levels of purine in whey protein prevent gout formation [52, 53].


Dosage and Best Time to Take

The dosage of whey protein depends on the goal of the individual, their lifestyle, and the amount of protein already in their diet.

A highly active or athletic person wanting to lose belly fat and preserve lean muscle should include a large amount of protein in their diet (0.68 – 1 g/lb of bodyweight). Less active lifestyles will require much less protein (0.36 g/lb of bodyweight) [54, 45].

Men should aim for 56 91 grams of protein per day while women should consume 46 75 grams per day [5556].

Taking whey protein supplementation consistently before a workout and/or after a workout has been shown to:

  • Increase physical performance [57]
  • Decrease workout recovery time [58]
  • Increase muscle size [59]
  • Increase strength [60]

User Reviews

Users of whey protein supplements report the following improvements in health:

  • Feeling stronger
  • More fueled
  • Having a greater motivation for exercising
  • Increased muscle gains
  • Improved recovery time
  • Reduced post-workout muscle soreness

Users also reported no side effects after using whey protein powder when mixed with water or milk. However, milk should be avoided in the case of lactose intolerance.

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