Side Effects of Whey Protein Isolate

Whey protein isolate is a supplement derived from the byproduct of cheese made from cow's milk. The byproduct is filtered to remove fat and lactose and then dried to a powdered form. According to, the purest and most concentrated form of whey protein is whey protein isolate. It is a popular product among body builders because of its powerful effect as a muscle builder, but it is a common belief that over-consumption of whey protein can cause side effects.

Scoops of protein powder. (Image: Lecic/iStock/Getty Images)

Side Effects

The common side effects of whey protein isolate may include headache, loss of appetite, fatigue, swelling, cramps and increased bowel movements. Other side effects may include damage to the kidneys or the liver, the development of osteoporosis or an allergic reaction. An allergic reaction is a serious medical emergency. The symptoms may include a rash or hives with swelling of the face, tongue or throat, along with difficulty breathing. Seek immediate medical care and attention if any of these symptoms are encountered.

Allergic Reaction

Whey protein contains lactose. Some individuals have lactose intolerance -- the inability to digest the lactose component of milk -- due to a deficiency of the lactase enzyme in the intestines. Consumption of whey protein by these individuals may cause an allergic reaction. Fortunately, there is only a small amount of lactose in whey protein which may minimize the severity of the allergic reaction. There are three types of whey proteins: whey protein concentrate, whey protein isolates and hydrolyzed whey. Lactose has been eliminated from the latter two whey proteins. This makes them suitable for individuals with lactose intolerance.


There is no scientific evidence to prove that consuming whey protein contributes to impaired kidney function. According to, kidney stress and kidney damage may occur when protein is consumed in excess on a long-term basis. This also applies to the over-consumption of whey protein.


The liver is the largest gland in the body with many important and complex functions. One of these functions is to process nutrients absorbed from foods in the body. According to, extremely high doses of whey protein supplements could overload the liver and cause damage. There are no scientific studies to prove this supposition.


According to, osteoporosis is a condition that decreases the strength and density of the bone. Osteoporosis increases the risk of bone fractures. Although there is no scientific evidence to prove the argument, it is believed that whey protein isolate taken in excess can cause mineral imbalance resulting in decreased bone density resulting in osteoporosis.

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