Sport, smoking and alcohol consumption are often discussed as factors that may affect testosterone levels in men. However, diet, including the source of protein—whether plant- or animal-based—may also play a role, according to new research conducted in Finland.
A study involving 2,546 men found that those with the highest intake of animal protein had lower testosterone concentrations than those with the lowest intake, while the opposite association was observed among men with the highest intake of plant-based protein.
Testosterone is the primary male sex hormone. It plays a role in regulating sexual function, muscle development and maintaining bone health, Euronews reports. Its levels vary depending on age, body weight and other factors, making it difficult to isolate the contribution of any single dietary component.
Higher protein intake from dairy products was associated with lower concentrations of total testosterone and sex hormone-binding globulin (SHBG). Meat protein intake, by contrast, was associated with lower SHBG concentrations, but not with total testosterone levels.
Researchers from the University of Eastern Finland analyzed data from men aged 42 to 60 living in eastern Finland. Their diets were recorded over four days between 1984 and 1989, while blood samples were used to measure total testosterone and sex hormone-binding globulin, a protein that affects testosterone concentrations in the blood.
Men in the group with the highest animal protein intake had an average total testosterone concentration that was 1.2 nanomoles per liter lower than that of participants with the lowest intake. The association was reversed for plant-based protein: men in the highest-intake group had testosterone concentrations that were 1.1 nanomoles per liter higher than those in the lowest-intake group.
In their analyses, the researchers adjusted for age, body mass index and several other factors related to diet, lifestyle and health status.
The Finnish study does not prove that animal protein lowers testosterone levels or that switching to a plant-based diet increases them.
The research used a cross-sectional design, meaning that it examined associations rather than cause-and-effect relationships.
"Although the differences in testosterone concentrations we observed were statistically significant, they were relatively small," said Miika Wynn-Ellis, a doctoral researcher at the University of Eastern Finland, in a university statement about the findings.
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