Warning for Sports Fans Who Consume Supplements Due to Kidney and Liver Problems


Brazil has the second highest number of gyms, totaling over nine million gym users in the country and this popularity has also increased the use of dietary supplements. However, the authors of the present study argue that gyms encourage the consumption of dietary supplements, resulting in the potentially unnecessary consumption of these substances.

They say this, coupled with a lack of guidance and oversight for the use of dietary supplements, can lead to overuse, raising concerns about safety, especially with regards to kidney and liver function. Studies on this potential link have so far led to conflicting results.

The current cross-sectional study, conducted by researchers at the University of Santa Cruz do Sul, Brazil, aimed to examine the association between dietary supplement consumption and alterations in markers of liver and kidney function in users of gymnasiums.

The study

Participants in this study were users of 31 gyms in the municipality of Santa Cruz do Sul, Rio Grande do Sul, Brazil. Gym users were asked to take an online dietary supplementation questionnaire and perform biochemical testing by peers and friends at gyms, via email and on social media.

The questionnaire contained closed and open questions divided into 3 sections: 1) socio-demographic characteristics: age, sex and level of education; 2) training habits: duration of exercise, intensity of exercise, type of exercise, additional activities performed; 3) supplement use: supplement use, duration of supplement intake, number of dietary supplements used, who provided the supplement prescription, type of dietary supplements used, reasons for supplement use.

Body mass index (BMI) and fat percentage were also assessed using a full body sensor scale.

Of the total number of gym users (n = 594, 266 men and 328 women, mean age 37 ± 14 years), a subset (n = 242, 114 men and 128 women) also gave samples of blood. Blood collection and anthropometry were performed in the Exercise Biochemistry Laboratory located at the University of Santa Cruz do Sul, Brazil. Blood samples were taken by a specialist in the morning and after a 10-12 hour fasting period.

The markers of liver function (liver function) analyzed were the enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST, which can be released into the bloodstream when liver cells are damaged), alkaline phosphatase (AKP) and gamma -glutamyltransferase (Gama-GT). The markers of renal function (renal function) analyzed were creatinine and urea (essential for the elimination of residual nitrogen, caused by the metabolism of proteins and amino acids).


Dietary supplements were consumed by 36.0% of gym users. Men had the highest use of dietary supplements (42.5%) and 8.3% reported consuming up to 5 types of supplements.

The data obtained revealed that people who took dietary supplements had a higher prevalence of mild alterations in the AST enzyme after adjustments for sex and age OR = 2.57; 95% CI = 1.09-6.07). Likewise, gym users who consumed dietary supplements showed a higher likelihood of mild urea alterations.

The team could not find an association between the number of supplements taken and markers of liver and kidney function.

Other markers of liver function and the creatinine marker were not associated with supplementation.

However, the researchers note that these results should be interpreted with caution. They did not assess food intake, specific supplements, dose completed, or use of other anabolic and androgenic steroids. The data are observational and therefore cannot exclude the possibility that other factors may have contributed to the results. Second, sample size can also be a limitation once there has been sample loss due to poor adherence of participants to performing biochemical tests (40% loss). In addition, the occurrence of changes in liver and kidney markers is low in people who exercise and use supplements, requiring a larger sample to significantly detect changes in these markers.

Third, this study is made up of individuals who received moderate and intense resistance training. Therefore, these results cannot be generalized to non-exercising / sedentary subjects, aerobic trainers, or other populations not examined in this study.

Future studies should further explain the mechanisms related to dietary supplement intake and impaired kidney / liver function.

The report concludes: “Our results showed that gym users who take dietary supplements are more likely to have mild alterations in the enzyme AST and urea. These data may aid in the analysis of future studies and alert patients. health professionals to define their goals and strategies that will help prevent disease and promote health in this population.

“Although our results showed slight alterations in renal and hepatic markers, these results do not indicate kidney and liver damage; however, they do indicate the need for biochemical monitoring of these markers to avoid possible alterations that could jeopardize the health of these people. “

Source: British Journal of Nutrition

Schlickmann, D., Molz, P., Brand, C., Dos Santos, C., Da Silva, T., Rieger, A. and Franke, S.

“Liver and Kidney Function Markers in Gym Users: The Role of Dietary Supplement Use”

doi: 10.1017 / S0007114521003652

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