Whey protein is a protein supplement frequently used to build muscle and prevent 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 .
Casein is the most abundant protein in milk, while whey protein accounts for roughly 20%.
Mechanism of Effect
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 .
Muscle growth can only be achieved if the rate of muscle building is greater than the breakdown of muscle protein .
Whey protein contains a large supply of the amino acid cysteine, which is a precursor of glutathione, a powerful antioxidant made by the body .
Glutathione is responsible for, among other things, preventing the type of cellular damage which could otherwise progress to cancer [5, 4].
Whey Protein Types
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 .
Whey protein concentrate is popular among athletes due to its large range of protein content (25 – 89%), lots of fat, and biologically-active components [6, 7].
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 .
Health Benefits of Whey Protein
Given that whey protein is a component of milk, it is considered safe to consume for most people (with exceptions for people with allergies or certain sensitivities). However, the FDA has not approved whey protein for any medical purpose or health claim, and it should never be used in place of something your doctor recommends or prescribes.
Possibly Effective For
1) Athletic Performance
In combination with strength training, whey protein increased strength and lean muscle mass in multiple clinical trials. In one clinical study, whey protein even increased running speed [9, 10, 11].
2) Body Composition
Strength and muscle mass decline with age .
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.
A 12-week study showed that 158 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 .
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 .
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 .
Leucine makes up 12% of the amino acids in whey protein and functions by stimulating muscle growth in the body .
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 prevented the degradation of muscle proteins .
The amino acids in whey protein also increase lean muscle growth after exercise .
3) Skin Health
A meta-analysis found that infants fed partially hydrolyzed whey formula were about half as likely to develop atopic dermatitis than infants fed cow’s milk formula. However, they were both at a disadvantage compared to breastfeeding .
In 84 mild to moderate psoriasis patients, 5-10 g of a specific whey protein product per day improved Physician’s Global Assessment (PGA) scores over 56 days .
Insulin-like growth factor-1 (IGF-1) contained in whey protein increases sebum production, which is linked to acne breakouts .
Whey protein spikes insulin causing an increase in skin cells, skin inflammation, and oil production resulting in increased acne formation [21, 22].
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of whey protein for any of the below-listed uses. Whey protein is considered safe to consume for most people, but it should never be used in place of something your doctor recommends or prescribes.
High protein diets improve satiety after a meal by increasing amino acid concentrations in the blood [23, 24].
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 .
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 .
Also, obese patients experienced a significant decrease in liver fat 4 weeks after adding whey protein to their diet .
5) Type 2 Diabetes
In type 2 diabetic subjects, whey protein taken during a meal increased the insulin response and significantly decreased blood glucose levels .
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 [29, 30].
6) Blood Pressure
Fermented milk supplemented with whey protein concentrate lowered blood pressure and cholesterol levels in both mice and healthy men .
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 .
Six weeks of whey protein supplementation can decrease blood pressure in overweight individuals .
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 .
A meta-analysis revealed that high doses of whey protein (around 45 g) may reduce CRP levels, but that lower doses do not appear to have an effect .
In a study of 31 elderly patients (65-90 years old) who had recently suffered a stroke, whey protein also reduced markers of inflammation .
IBD, like Crohn’s disease or ulcerative colitis, involves chronic inflammation in the digestive tract. Whey protein reduced gut inflammation and damage to the intestinal lining by increasing both antioxidant defenses and good bacteria in 30 patients with Crohn’s disease [37, 38, 39].
Low-density lipoprotein cholesterol (LDL-cholesterol) or “bad” cholesterol is a major risk factor for heart disease, heart attack, and stroke .
70 overweight patients taking high doses of whey protein supplements saw a significant decrease in bad cholesterol .
However, a meta-analysis only showed an overall reduction in blood triacylglycerol with no effect on LDL-cholesterol .
Animal Research (Lacking Evidence)
No clinical evidence supports the use of whey protein for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
9) Digestive Health
Whey protein is considered a prebiotic that helps good bacteria in the gut and, according to studies of human gut bacteria, may suppress the growth of bacteria associated with obesity .
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 [43, 44, 45].
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 .
In rat models, 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 .
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; however, this has yet to be investigated in humans [48, 47].
For the time being, there is not nearly enough evidence to support using whey protein alongside conventional cancer therapies. If you are currently undergoing treatment, talk to your doctor before using whey protein.
1) Kidney Stones
Lots of protein in the diet puts a large amino acid load to the kidneys, increasing the risk of kidney stone formation .
Resistance training may counter damage to the kidneys caused by a high protein diet .
2) Kidney Damage
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 [51, 52].
3) Digestive Discomfort
Whey protein does contain lactose (a sugar found in milk) and those with lactose intolerance may experience cramping and diarrhea .
Whey protein concentrate and whey protein isolate contain small amounts of lactose .
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 .
Evidence suggests that anti-inflammatory properties and low levels of purine in whey protein prevent gout formation [55, 56].
Dosage and Timing
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 may 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) [57, 51].
Experts recommend protein intakes of 56 – 91 grams per day for men and 46 – 75 grams per day for women [58, 59].
Taking whey protein supplementation consistently before a workout and/or after a workout has:
- Increased physical performance 
- Decreased workout recovery time 
- Increased muscle size 
- Increased strength 
Users of whey protein supplements report the following improvements in health:
- Feeling stronger
- Geater 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.