Animal protein linked to lower testosterone, plant protein to higher, study finds

New research associates consuming more animal protein with reduced blood testosterone, whereas plant-based sources are linked with elevated levels. 

Researchers from the University of Eastern Finland analyzed data from 2,546 men aged 42–60, finding that those consuming the most animal protein had total testosterone levels 1.2 nmol/L lower on average than those with the least intake. 

Those with the highest plant protein intake had a 1.1 nmol/L higher level than those with the lowest. 

No causal link established

The cross-sectional study in the International Journal of Food Sciences and Nutrition noted that the statistical difference was significant but small. It also cautions that the research does not establish a causal relationship, adding that associations could be related to other aspects of the diet or metabolic factors.

“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,” says doctoral researcher Miika Wynne-Ellis from the University of Eastern Finland.

Testosterone is the primary male sex hormone that supports muscle and bone health alongside sexual function. The researchers explain that age, excess weight, and lifestyle are some factors that determine the level of this hormone.

However, they point out that very few studies have analyzed the link between testosterone levels and protein intake.

SHBG concentration patterns

In their study, the researchers used data from the ongoing Kuopio Ischemic Heart Disease Risk Factor Study at the University of Eastern Finland. They assessed the men’s diet using four-day food records between 1984 and 1989, and concentrations of testosterone and sex hormone-binding globulin (SHBG) were measured in blood samples. The researchers point out that SHBG impacts total testosterone concentrations in the blood by binding the hormone into the blood.

They calculated free testosterone as a result, which is the biologically active fraction.

The study divided the men into four groups based on their protein intake. Researchers observed that SHBG concentrations followed the same pattern, lower with higher animal protein, and higher with higher plant protein.

The team notes that they adjusted for participants’ age and body mass index, as well as several other dietary, lifestyle, and health-related factors.

According to further analysis, higher dairy protein was linked with lower total testosterone and SHBG concentrations. 

Additionally, researchers observed that higher intake of plant protein from vegetables and non-cereal sources was associated with higher total testosterone levels. Non-grain plant sources included vegetables, legumes, seeds, nuts, fruits, berries and mushrooms.

They add that meat intake was linked to lower SHBG concentrations but not to total testosterone concentrations. 

Meat and masculinity perception

Nutrition Insight previously explored the rise of carnivore diets linked to meat and masculinity myths.

A recent Physicians Committee for Responsible Medicine poll found that 53% of US men link carnivore diets with masculinity, while only 10% say the same about plant-based diets. The poll also found that 63% of men would change their diet after learning that meat-heavy eating can harm health.