Bodybuilding supplement practices can harm kidneys, study says

By Hank Schultz contact

- Last updated on GMT

©Getty Images - Terri Lee-Shield Photography
©Getty Images - Terri Lee-Shield Photography

Related tags: Sports nutrition sector, Sports & Active Nutrition Summit USA, Sports nutrition, Sports nutrition products, Bodybuilding, kidney disease

A new review raises an alarm about some bodybuilding supplementation practices that can damage the kidneys. But an expert with decades of experience in the field said extreme practices followed by some athletes who may have underlying conditions should not cast a pall on all regimens.

The new study was published in the International Journal of Environmental Research and Public Health​. It was the work of researchers associated with two universities and a hospital in England.

The researchers collected 13 studies published since the year 2000 that described incidences of kidney disease in bodybuilders.  The reports covered 75 bodybuilders in total.

The authors broke out effects of supplementation strategies on kidney function among these athletes into several buckets. Those include protein dosing, creatine supplementation, vitamin use as well as several that pertain to the legal (or not legal) pharmaceutical realm including the use of diuretics, NSAIDs as well as supplementing with various anabolic steroids.

High protein intakes only weakly implicated

The review found that bodybuilders typically consume far more protein than health authorities recommend for the general population.  The intakes can range from 2 grams per kilogram of bodyweight a day up to 5g/kg or even more.  In one report of bodybuilders with kidney damage the intakes hit an incredible peak of 30g/kg a day.  For a 95 kg bodybuilder that would equate to more than 10,000 calories a day in protein alone.

Yet the authors also stated that even with these high intakes, protein by itself was not universally implicated in kidney problems.

“Other studies have found no detrimental effects of isolated high-protein diets, albeit consumed for relatively brief periods,”​ the authors stated.

More concern about creatine, high vitamin doses

Creatine supplementation by the bodybuilders was similarly elevated far above what is recommended for average individuals.  Creatine monohydrate was the form mentioned in research, and for the average person 3 to 5 grams a day is considered to be enough.  The bodybuilders commonly took as much as 20 g/day in a ‘loading’ phase and then cut back to a lower maintenance dose.

The authors said such high creatine dosages can be associated with some renal problems.  Creatine is normally metabolized to creatinine, but when high amounts are in the blood stream some of it can enter a different metabolic cascade that results in the production of methylamine and formaldehyde, which can be potentially cytotoxic. 

Similarly, some of the case studies detailed in the reviewed studies showed bodybuilders ingesting vitamins A, D and E at far higher dosages than recommended.  Sometimes this was done by injection with a substance known by the common name of ADE.  Some bodybuilders were injecting themselves with dosages greater than those recommended for cattle, the researchers said.  At least one individual was found to be taking as much as 40,000 IU/day of vitamin D.

The researchers concluded these practices put on the bodybuilders on a path toward kidney damage.

“Bodybuilders routinely engage in many nutritional and non-nutritional practices potentially harmful to the kidney. There is stronger evidence of damage caused by anabolic androgenic steroids and, particularly, high doses of vitamins A, D and E, than there is for high protein intake and creatine supplementation.  . . . Further research is required to identify the clinical and subclinical harm associated with individual practices and combinations, to enable the provision of appropriate advice,”​ the authors concluded.

Expert: Take alarm bells with grain of salt

Sports nutrition pioneer Susan Kleiner, PhD, did some of her early research on bodybuilders. She has decades of experience guiding strength and endurance athletes as a clinical nutritionist and principal in the firm High Performance Nutrition LLC. She said the new review paper provides a good overview of practices followed by some, but by no means all bodybuilders.  And she said the author’s conclusions shouldn’t be taken to cast aspersions on the use of supplements in general.

Fro one thing, the data set is not very large, Kleiner noted.  And she said that the authors acknowledged that most of the studies did not measure kidney function in a way that gives the best picture of renal health individuals with far more muscle mass than the average individual, something that practitioners should take note of.

And, she said while the high protein intakes look eye-popping to some, they’re not inherently dangerous.

“High protein diets, and creatine supplementation according to dosing recommendations do not cause disruption to kidney health,”​ Kleiner said.

People with compromised kidney function should generally not eat a high protein diet, but dialysis may reduce intrinsic creatine production and creatine supplementation may be indicated,”​ she added.

Nutritionists as guides

“None of this is news to those of us who work in this field. However it acts as a reminder to always check the health of your client/patient prior to giving recommendations that may have unintended health consequences. Additionally, ask clients what their current supplementation practices are, both nutritional and non-nutritional. As health care providers, our role is to educate, motivate and guide patients/clients toward not only their performance goals, but also health. We often will have better information on health consequences that we can share with clients so they make more informed decisions,”​ Kleiner concluded.

Source:International Journal of Environmental Research and Public Health
2022, 19​(7), 4288; https://doi.org/10.3390/ijerph19074288
Nutritional and Non-Nutritional Strategies in Bodybuilding: Impact on Kidney Function
Authors: Tidmas V, et al.

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