Do protein shakes have side effects?

Updated April 17, 2017

Protein shakes are used by health buffs, athletes and body builders to enhance performance, lose weight or to supplement nutrition. Protein is seen as a vital nutrient for building skin, bone and, most important, muscle. Protein shakes come in a wide variety of flavours, with nutritional content ranging from 100 per cent protein to a little amount of protein with high amounts of carbohydrates and sugar. A normal serving of protein is less than 40g per meal. If you go beyond that, there is a danger of experiencing side effects--some of which could be deadly.


Protein shakes are a protein-rich food. They make blood more acidic. Your body will try to neutralise the acid by pulling calcium from the bones, which can weaken the bone structure and possibly cause breaks and fractures. Researchers at the University of California at San Francisco studied 9,000 women and found that women who consumed foods with a higher level of acidity, such as meats and hard cheeses, had nearly four times more hip fractures than those who didn't. A diet high in protein, such as from protein shakes, can directly contribute to frail bones or osteoporosis.

Kidney Stones

Large amounts of calcium in the blood due to excessive protein consumption can cause calcium deposits to form, creating what we call kidney stones. These tiny, crystallised deposits normally pass through the urine stream with an enormous amount of pain and can be accompanied by lower abdominal pain, night sweats, blood in the urine and night fevers. Insufficient hydration can also be a major factor in developing kidney stones.


With an unbalanced diet--such as too much protein and not enough carbohydrates--the body can go into a state known as ketosis. This is starvation mode, in which the body breaks down fat into ketones--which it then uses as an alternative to glucose for fuel. Some medical professionals believe that ketosis is a dangerous state that is extremely hard on the liver, and may be potentially life-threatening. Other doctors, particularly those who believe in low-carbohydrate diets, disagree with this conclusion and say that ketosis is beneficial for the body.


According to a study done at the University of Connecticut by the Department of Nutritional Sciences, hydration of the body is directly affected by how much protein is found in your diet. Researchers found that higher levels of protein meant an increased amount of nitrogen in the blood, indicating abnormal kidney function. The students who had high-protein diets had more concentrated urine, yet felt no change in thirst. Based upon their findings, the researchers recommend that anyone on a high-protein diet consume greater amounts of water than the average recommendation of 8 to 10 glasses per day in order to avoid dehydration.

Food Allergy

The most common food allergy to worry about with certain protein shakes or supplements is lactose intolerance. If you are lactose intolerant, taking whey protein can cause unpleasant side effects such as bloating, upset stomach and cramps. The best way to avoid these side effects is to take whey protein isolate, which contains less than 1 per cent lactose, or find a brand with no lactose. Some brands extract the lactose from the whey to make it safer for people with food allergies. The best way to avoid all side effects of protein shakes and excessive protein consumption is to eat a balanced diet, drink more than 8 glasses of water a day and limit protein to less than 40g per serving.

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About the Author

Sarena Fuller has been writing professionally since 2003. She has written for e-commerce sites, architectural firms, doctors and fashion companies. Her writing experience varies from technical writing to hair and beauty, alternative medicine and eco-friendly living. Fuller holds a Bachelor of Arts in English from the University of Arizona.