Background: Higher endogenous testosterone levels are associated with reduced chronic disease risk and mortality. Since the mid-20th century, there have been significant changes in dietary patterns, and men's testosterone levels have declined in western countries. Cross-sectional studies show inconsistent associations between fat intake and testosterone in men.
Methods: Studies eligible for inclusion were intervention studies, with minimal confounding variables, comparing the effect of low-fat vs high-fat diets on men's sex hormones. 9 databases were searched from their inception to October 2020, yielding 6 eligible studies, with a total of 206 participants. Random effects meta-analyses were performed using Cochrane's Review Manager software. Cochrane's risk of bias tool was used for quality assessment.
Results: There were significant decreases in sex hormones on low-fat vs high-fat diets. Standardised mean differences with 95 % confidence intervals (CI) for outcomes were: total testosterone [-0.38 (95 % CI -0.75 to -0.01) P = 0.04]; free testosterone [-0.37 (95 % CI -0.63 to -0.11) P = 0.005]; urinary testosterone [-0.38 (CI 95 % -0.66 to -0.09) P = 0.009]; and dihydrotestosterone [-0.3 (CI 95 % -0.56 to -0.03) P = 0.03]. There were no significant differences for luteinising hormone or sex hormone binding globulin. Subgroup analysis for total testosterone, European and North American men, showed a stronger effect [-0.52 (95 % CI -0.75 to -0.3) P < 0.001].
Conclusions: Low-fat diets appear to decrease testosterone levels in men, but further randomised controlled trials are needed to confirm this effect. Men with European ancestry may experience a greater decrease in testosterone, in response to a low-fat diet.
Keywords: Androgen; Dietary fat; Low-fat diet; Meta-analysis; Sex hormone; Testosterone.
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