What Are the Side Effects of Protein Supplements?

Side Effects of Protein

Protein is a vital part of every diet, no matter who you are, but it’s especially important for hard-training strength athletes who constantly tear down  their muscles and need amino acids to repair the damage.  Protein supplements, in particular, are a convenient and powerful way to help meet your protein needs and can provide a training boost that “regular” food cannot.

For years, though, heavy protein consumption has been blamed for a host of side effects of protein, some warranted and some not, that can make you question whether you should REALLY be consuming the amount that most bodybuilders recommend for best results — around one gram per pound of bodyweight each day.

To give you some perspective on the subject, here is a quick rundown of the possible side effects of protein, along with the real scoop on each one.

Weight Gain

The whole point of taking supplements like protein and creatine is to get stronger and build muscle.  For most athletes, adding weight is no easy feat, so the weight bump that protein can provide is welcomed.  For those involved in weight-restricted activities like wrestling, though, weight gain can be a problem.  If that’s where you find yourself, then you will have to weigh the benefits of getting bigger and stronger with the prospect of having to move up a weight class.


Researchers from the University of Connecticut reported in 2002 that athletes consuming high-protein diets showed abnormally high urea levels and saw their hydration levels decrease significantly compared to periods when they ate less protein.  This study lends evidence to anecdotal reports of dehydration among those consuming high-protein diets and points to the need for athletes to drink lots of water.

Liver Damage

Some animal studies suggest that loading up on protein may be harmful to your liver after a period of very low protein consumption.  Theories about why this may be center on the quick build up of ammonia in the liver, but none of the studies suggest any specific link between high protein intake and liver damage in healthy people.

Kidney Damage

Medical professionals have long wagged their fingers at bodybuilders, telling us that our high-protein diets could damage our kidneys.  For the most part, there has been little evidence that this is actually the case for people with healthy kidneys, but recent research out of the University of Granada in Spain does raise at least the possibility of kidney damage from high-protein diets — for rats.  The scientists found that rats fed a high-protein diet — 45% of calories — experienced a 22% increase in kidney weight and a 13% increase in kidney size over the course of 12-week study.

While rats are not humans, our organs are remarkably similar, and this is one of the first studies to actually demonstrate possible kidney damage from protein ingestion.

Heart Disease

High-protein diets have long been associated with an increase in risk for heart disease, but that’s largely a misleading claim.  For most of modern human history, “high-protein” has meant heavy consumption of fatty red meat and pork, both of which can be major contributors to high cholesterol and other risk factors.   These days, there is little reason to eat tons of inferior meat products, and high-quality protein powders are virtually fat- and cholesterol free.

Gastrointestinal Distress

Like heart disease, gastrointestinal problems associated with protein intake often come down to WHICH protein you eat.  People with lactose intolerance will obviously want to avoid eating a ton of dairy products, and those prone to constipation will want to go easy on the slabs of meat.  Like any food, protein can cause stomach upset and flatulence if you eat too much of the wrong kinds, but you can work around most of these issues simply by choosing a different protein source.

Are Protein Supplements Worth the Risk?

Given this list of possible negative side effects of protein, you might be wondering whether protein supplements are even worth the risk.  After all, what good isincreased muscle mass and strength if you end up sick in the process?

The good news is that most research studies have found little evidence that extra protein will cause any problems for most athletes.  The cases where issues HAVE popped up have usually involved people with preexisting conditions, so it’s always important to know how good your overall health is before diving into any nutritional changes.

If you have any concerns about possible side effects, talk with your doctor before increasing your protein intake or adding a protein powder to your diet.  For most lifters, though, protein supplements are a safe and effective way to get more out of your training program.

Become a SuperHuman: Naturally & Safely Boost Testosterone

The course that helps you hack diet, exercise, & habits to safely boost your testosterone!