November 13, 2026, 7:36 pm | Read time: 4 minutes
A Finnish study involving more than 2,500 men shows: Those who consume a lot of animal protein have, on average, lower total testosterone levels. In contrast, plant-based protein was associated with higher levels. What does this mean for nutrition?
Protein is essential for the body. It supports muscle building, tissue maintenance, and numerous metabolic processes. Especially for men who regularly engage in strength training, protein-rich foods such as meat, dairy products, and eggs are often on the menu. But could the source of the protein also be related to hormone balance?
A study from Finland examined exactly this connection.1 The results suggest that the type of protein consumed could play a role in testosterone levels: A higher intake of animal proteins was associated with lower total testosterone levels. The opposite trend was observed with plant-based protein.
How was the connection between protein and testosterone studied?
For the study, a research team analyzed data from 2,546 men aged between 42 and 60. They participated in the Finnish Kuopio Ischaemic Heart Disease Risk Factor Study. The dietary data were from 1984 to 1989.
The participants kept dietary records for four days. Additionally, the researchers examined blood samples to determine, among other things, the concentrations of total testosterone and sex hormone-binding globulin (SHBG). SHBG is a transport protein that binds sex hormones in the blood and thus also influences how much testosterone is freely available.
The researchers then compared the hormone levels of men with different intakes of animal and plant-based protein. They considered various influencing factors, including age, body weight, alcohol consumption, smoking, and physical activity.
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More animal protein, less total testosterone
The result: Men in the quartile with the highest intake of animal proteins had, on average, a total testosterone level 1.2 nanomoles per liter lower than men in the quartile with the lowest intake. The researchers also found corresponding differences in SHBG: A higher intake of animal protein was associated with lower levels, while a higher intake of plant protein was associated with higher levels.
With plant-based protein, the opposite relationship was observed. Men with the highest intake of plant proteins had, on average, a total testosterone level 1.1 nanomoles per liter higher than men with the lowest intake.
However, differences were observed when looking at individual food groups. Milk protein and fermented milk protein were particularly associated with lower total testosterone levels. In contrast, no statistically significant connection with total testosterone could be established for meat protein, fish, and eggs. However, a connection with lower SHBG levels was observed for meat protein.
Does this mean men should eat less meat?
No, this conclusion cannot be drawn from the study. The study shows a statistical correlation but no proof that animal protein actually lowers testosterone levels. Nor is it proven that more plant-based protein automatically leads to higher hormone levels.
The differences should not be overemphasized either. The researchers examined blood values and not specific health outcomes such as muscle strength, libido, or fertility. Additionally, dietary habits were recorded over only four days, and blood values were determined at a single point in time.
Another limitation: The data are from the 1980s and pertain to men from a specific region in Finland. Whether the results can be applied to younger men or other populations is therefore uncertain.
For nutrition, this means: The study provides an interesting indication that not only the amount but possibly also the source of protein is related to hormone balance. It is not a reason to generally avoid meat or dairy products. But it also underscores that for muscle building, animal proteins are not always necessary. A balanced diet with different plant and animal protein sources remains crucial.