Updated

A University of Eastern Finland study of 2,546 men aged 42 to 60 in eastern Finland linked higher animal protein intake to lower testosterone and plant protein to higher testosterone. The study, published in the International Journal of Food Sciences and Nutrition, is part of the Kuopio Ischaemic Heart Disease Risk Factor Study. Men with the highest animal protein intake had average total testosterone 1.2 nmol/l lower than those with the lowest, while men with the highest plant protein intake had levels 1.1 nmol/l higher than those with the lowest. The men recorded their food over four days between 1984 and 1989, and blood samples measured total testosterone and sex hormone-binding globulin (SHBG). Dairy protein was associated with lower total testosterone and SHBG, and plant protein from vegetables and sources other than cereals with higher total testosterone. Meat protein was linked to lower SHBG but not to total testosterone. The associations held after accounting for age, body mass index and other factors. The researchers stressed that the differences were statistically significant but relatively small, and that it is unknown whether they have any health consequences. Because the study was cross-sectional, it cannot show that protein changes cause hormone changes, nor whether protein affects testosterone production or how the hormone works in the body. Doctoral Researcher Miika Wynne-Ellis said the study cannot show whether the differences matter for health.