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Rooibos tea improves sperm concentration and functions in the rat
Rooibos tea (Aspalathus linearis) grows in the Western Cape region of South Africa. Unfermented and fermented rooibos contain high levels of antioxidants which inhibit reactive oxygen species (ROS). As spermatozoa are highly susceptible towards ROS, rooibos tea may improve sperm functions. To test this hypothesis, male rats were given 2% or 5% unfermented or fermented rooibos tea as sole source of drinking for 52 days. No significant alterations were observed in body weight gain, reproductive organs weight and serum antioxidant capacity, but testosterone levels were slightly lowered. Seminiferous tubules displayed complete spermatogenesis with abundant sperm in the lumen. However, a significant decrease in tubule diameter and germinal epithelial height were observed. In the epididymides, epithelial height of caput region showed a significant increase. Drinking of unfermented rooibos significantly enhanced sperm concentration, viability and motility. Fermented rooibos also boosted sperm concentration and motility and significantly improved sperm vitality. All teas caused a small increase in spontaneous acrosome reaction which was only significant for 2% fermented rooibos. Creatinine was significantly enhanced in all treated rats, consistent with significant higher kidney weights. Activity of liver marker ALT was significantly reduced, whereas the effect on AST varied: 2% unfermented rooibos significantly decreased AST level but the 5% fermented tea increased it.
In conclusion, rooibos tea significantly improved sperm concentration, viability and motility which is beneficial for male fertility and might be attributed to its high level of antioxidants. The increased level of acrosome reaction caused by rooibos may be a reason for concern as this could inhibit the fertilization process. Also, the prolonged exposure of rooibos might result in subtle structural changes in the testis. Intake of large amounts of rooibos tea may also impair liver and kidney function.