Vitamin C maintains endurance athletes testosterone levels

Performing endurance sports reduces testosterone levels. [Eur J Appl Physiol. 2003 Apr;89(2):198-201.] This happens, for example, if you run for longer than 45 minutes. [Eur J Appl Physiol. 2005 Aug;94(5-6):505-13.] Pharmacologists at the BJ Govt Medical College in India did an animal study which seems to have uncovered a surprisingly simple way for endurance athletes to limit the reduction in their testosterone level: supplementation with vitamin C.

Vitamin C and testosterone

Ten years ago researchers from Firat University published an animal study in which a megadose of vitamin C boosted testosterone levels. [Theriogenology. 2005 Apr 15;63(7):2063-72.] Converting the figures, an adult human would need 3 to 7 g vitamin C a day to induce a modest rise in testosterone level.

In the animal study that the Indian researchers published in the Journal of Clinical and Diagnostic Research male rats were given less extreme doses. The human equivalent of these would be about 140, 280 and 420 mg per day.


The researchers got rats to swim to the point of exhaustion on 15 consecutive days [Exercise; Stress]. Some of the lab animals did not swim [Normal].

Testosterone level

The fortnight of physical exertion lowered the rats’ testosterone level, as the figure below shows. When the rats were given vitamin C 30 minutes before they started swimming, however, the decrease in testosterone was less.




Vitamine C


The physical exercise reduced the rats’ fertility, probably because of the release of free radicals during their exertions, which damaged the testes. Supplementation only partially negated the reduction in sperm quality, the table above shows.

Sexual effects

The physical exertion reduced the percentage of pairings the researchers discovered when they placed sexually mature females in a cage with the lab rats. Administration of vitamin C limited the decline in sexual interest. Copulatory index = an indicator of the animals’ interest in sex.



“Vitamin C supplementation improves the stress induced reproductive infertility possibly mediated through an increase in testosterone and an antioxidant effect”, the researchers write.

Effect of vitamin C on male fertility in rats subjected to forced swimming stress.



Stress is defined as a general body response to initially threatening external or internal demands, involving the mobilization of physiological and psychological resources to deal with them. Recently, oxidative stress has become the focus of interest as a potential cause of male infertility. Normally, equilibrium exists between reactive oxygen species (ROS) production and antioxidant scavenging activities in the male reproductive organs. The ascorbic acid is a known antioxidant present in the testis with the precise role of protecting the latter from the oxidative damage. It also contributes to the support of spermatogensis at least in part through its capacity to maintain antioxidant in an active state.


Group1: Normal Control animal received Distilled water, Group 2: Positive control (Only Stress), Group 3: Normal rats received an intermediate dose of Vitamin C (20mg/kg/day), Group 4: Stress + Low dose Vitamin C (10mg/kg/day), Group 5: Stress+ Intermediate dose Vitamin C (20mg/kg/day), Group 6: High dose Vitamin C (30mg/kg/day). On 16(th) day effect of stress on body weight, Reproductive organ weight, sperm parameters, and hormonal assay was studied.


In the present context, in stress group the sperm count, motility, testicular weight declined significantly. The intermediate dose and high dose of vitamin C showed significantly increased effect on the sperm count and motility.


Various physiological changes produced force swimming indicates that swimming is an effective model for producing stress in albino rats. The results suggest that Vitamin C supplementation improves the stress induced reproductive infertility due to both their testosterone increase effect and their antioxidant effect.

PMID: 25177581 [PubMed] PMCID: PMC4149087