Scientists discover men who eat more meat have lower testosterone levels in worrying results of new study

Men who got more of their protein from animal products had lower testosterone levels than those who ate the least, according to research involving more than 2,500 men.

The study found the opposite pattern among men who ate more plant protein: their testosterone levels were higher on average.

Researchers stressed, however, that the differences were small and the findings do not show that animal foods cause testosterone to fall.

The University of Eastern Finland study, published in the International Journal of Food Sciences and Nutrition, examined 2,546 Finnish men aged 42 to 60.

Researchers compared the men's diets with blood test results. Those with the highest animal protein intake had average testosterone levels 1.2 nanomoles per liter lower than those with the lowest intake.

For men with the highest plant protein intake, levels were 1.1 nanomoles per liter higher than in the group eating the least.

The University of Eastern Finland study examined 2,546 men aged between 42 and 60. (Getty Stock Image)

How does animal protein relate to testosterone levels?

The team used four-day food records collected between 1984 and 1989, alongside blood samples measuring testosterone and a protein called sex hormone-binding globulin. This protein helps carry sex hormones through the bloodstream.

Participants were split into four groups based on protein intake.

Researchers also accounted for age, body mass index, other dietary habits, lifestyle and health.

A closer look found dairy protein was associated with lower testosterone and lower levels of the hormone-carrying protein. Protein from vegetables and other plant foods, excluding cereal products, was linked with higher testosterone.

Meat protein, however, was associated with lower levels of the hormone-carrying protein, but not with lower total testosterone. The overall animal-protein finding should therefore not be taken as proof that eating meat alone lowers testosterone.

Plant protein intake was associated with higher testosterone levels among men in the University of Eastern Finland study. (Getty Stock Image)

Can eating more plant protein raise testosterone?

The study doesn't show that changing someone's diet alone will change their testosterone levels. It examined people's food intake and hormone levels, rather than giving participants a diet and tracking the results over time.

The researchers said other parts of a person's diet, or differences in how their body processes food, could help explain the patterns. The findings cannot establish whether protein sources affect testosterone production or how the hormone works.

Testosterone plays an important role in men's sexual function, muscles and bones. Levels can also be influenced by age, excess weight and lifestyle, so diet is only one possible factor.

Doctoral researcher Miika Wynne-Ellis, from the University of Eastern Finland, said: "Although the observed differences in testosterone concentrations were statistically significant, they were relatively small. Based on this study, it is not possible to infer whether these differences have implications for health."

The findings came from the university's ongoing Kuopio Ischaemic Heart Disease Risk Factor Study. Although the food records date back to the 1980s, the analysis compared reported protein intake with testosterone measurements.

For now, the results show an association, not a cause-and-effect relationship.

Further research is needed to establish whether changing the balance of animal and plant protein has any meaningful impact on men's hormone levels or health.

The researchers observed existing diets, rather than testing a planned change in what participants ate.