When it comes to testosterone, most men think about exercise, smoking, or alcohol. But a new study from Finland suggests that the source of dietary protein—whether from animals or plants—might also matter.
Researchers at the University of Eastern Finland analyzed data from 2,546 men aged 42 to 60 living in eastern Finland. Their diets were recorded over four days between 1984 and 1989, and blood samples were used to measure total testosterone and sex hormone-binding globulin (SHBG), a protein that affects how much testosterone is available in the blood.
The results, published in the journal Food & Function, showed contrasting associations. Men with the highest intake of animal protein had average total testosterone concentrations that were 1.2 nanomoles per litre lower than those with the lowest intake. In contrast, men with the highest intake of plant protein had concentrations 1.1 nanomoles per litre higher than those with the lowest intake.
Breaking it down further, higher dairy protein intake was linked to lower total testosterone and SHBG, while meat protein was associated with lower SHBG but not with total testosterone. Meanwhile, plant protein from vegetables and non-cereal sources was linked to higher total testosterone.
What does this mean for men's health?
Testosterone is a key male sex hormone, involved in sexual function, muscle development, and bone health. Its levels naturally decline with age and are influenced by body weight and other factors, making it difficult to isolate the effect of any single dietary component.
The researchers adjusted their analyses for age, body mass index, and a range of dietary, lifestyle, and health-related factors. Still, the study is cross-sectional, meaning it can only show associations, not cause and effect.
“Although the observed differences in testosterone concentrations were statistically significant, they were relatively small,” said Miika Wynne-Ellis, a doctoral researcher at the University of Eastern Finland, in the university’s announcement.
In other words, the study does not prove that eating more meat lowers testosterone or that switching to a plant-based diet boosts it. The differences, while measurable, may not be clinically meaningful for most men.
Still, the findings add to a growing body of research on how diet affects hormonal health. Previous studies have linked green spaces near home to better health outcomes, and this Finnish work suggests that the quality of protein sources could be another factor worth considering.
For men in Finland and across Europe, where diets vary widely—from the Mediterranean pattern in the south to more meat-heavy diets in the north—the results may prompt a closer look at protein choices. But experts caution that a balanced diet, rather than a single nutrient, is what matters most.
“We need to be careful not to overinterpret these findings,” said Dr. Laura Mäkelä, a nutrition researcher at the University of Helsinki who was not involved in the study. “The associations are interesting, but they don't tell us whether changing your diet will change your testosterone levels.”
The study's long follow-up period—over 30 years—is both a strength and a limitation. It provides a long-term snapshot, but diet was only recorded once, and testosterone levels can fluctuate over time.
Future research could use repeated measurements and controlled dietary interventions to clarify the relationship. Until then, men looking to maintain healthy testosterone levels should focus on overall lifestyle factors like regular exercise, adequate sleep, and a varied diet rich in fruits, vegetables, and whole grains.
As the debate over plant-based versus animal-based diets continues, this Finnish study offers a nuanced piece of the puzzle—one that underscores the complexity of nutrition and hormonal health.
