Whey Protein Side Effects

When considering whey protein side effects, you must remember it’s only food, not a drug. It is produced from cow’s milk and is a byproduct from producing cheese (for more info read what is whey protein).

Let’s look at some of the most common concerns regarding whey protein side effects:

Whey Allergies

Because whey comes from milk, those who are lactose intolerant MAY have trouble digesting whey protein. Lactose is milk sugar, and lactose intolerant people lack the enzyme needed to break it down properly. I say that they may have troubles because while whey protein does contain lactose, it is very little compared to cow’s milk.

Different processing methods result in a varying amount of lactose. (See whey protein info). Isolate typically has less lactose because of the high processing techniques which results in more protein, but less fats and milk sugar (lactose). The only way to know is to try using whey protein and see how you react. Most people are fine with a little bit of lactose, but if you do suffer from this whey protein side effect, then try a whey isolate or a vegan protein powder. For more info on your options, see whey protein allergy (link).

Kidney Function

Another suggested whey protein side effect is that high amounts of whey protein will cause kidney damage. I believe a lot of this theory came from the effect a high-protein diet can have on a person with renal disease. If you suffer from abnormal kidney function, then yes, too much protein can cause problems. But there are no studies suggesting that high intakes of whey protein will cause any harm to someone with healthy kidneys.

The kidney’s primary function is to filter the blood — about 1.5 quarts per minute. Healthy kidneys will filter protein out of the blood and then reabsorb it for use in the body. When protein intake is increased, this action of the kidneys is increased as well in order to compensate or adapt.

This is not kidney failure — this is adaptation! Just like how your heart will grow in size after training in order to handle more blood flow. Your kidneys increase the rate in which they can handle increased protein intake. Studies have shown that while this occurs, there is no protein in the urine (proteinuria), suggesting that the kidneys are not overloaded.

There are also no studies linking whey protein consumption to kidney stones. For more information and a great study see this website.

Liver Function — Whey Protein Side Effects

Just like with the kidneys, the liver processes protein as well. Same story with the liver — unless you have a poorly functioning liver, your body can handle whey protein just fine. No one knows the exact amount that is right for everyone, and it gets more complicated when liver conditions are involved. If you do suffer from liver disease, there are many blood tests that are available to see if you are over consuming protein.

There currently are no studies showing liver damage as a result of consuming whey protein powder. One study in fact suggested that whey can actually improve liver function!


When considering whey protein side effects, osteoporosis seems like a major concern. Osteoporosis involves much more than how much protein you eat, so it’s impossible to make this claim. The theory comes from the fact that protein consumption results in a net acid load to the body. To counteract this acidity, the body pulls calcium from bones as a buffer.

While this effect is real, it’s important to know there is no research showing that athletes that use whey protein have less bone density. It is of course wise to consume vegetables and fruits which have a net alkaline load on the body to balance this effect.

Overall, whey protein is a safe and effective way to add beneficial protein into your diet. As long as you are eating a complete diet full of fruits, vegetables, nuts and other sources of protein, there really are no whey protein side effects to worry about.

Check out all the benefits of whey protein.