Animal and Plant Protein Linked to Opposite Testosterone Levels in Finnish Men, but the Gaps Are Small
A University of Eastern Finland analysis of 2,546 middle-aged men found more animal protein went with lower testosterone and more plant protein with higher, gaps the authors call small.
Outspoken Digest Nutrition Desk
Wednesday, October 28, 2026/2 min read
Online, protein and testosterone are tangled together in claims about meat, masculinity and plants. A new paper from the University of Eastern Finland adds data to the argument, and a good deal of caution. It finds that men who ate the most animal protein had slightly lower testosterone than men who ate the least, while men who ate the most plant protein had slightly higher.
The study, in the International Journal of Food Sciences and Nutrition, was announced by the university on 27 October and covered on Wednesday by News-Medical. It is observational, and the lead researcher says it cannot show that the food caused the difference.
What did the Finnish study measure?
The researchers used the Kuopio Ischaemic Heart Disease Risk Factor Study, a long-running cohort in eastern Finland. They analysed 2,546 men aged 42 to 60. Diet was recorded in four-day food records collected between 1984 and 1989, and blood samples were analysed for total testosterone and sex hormone-binding globulin, or SHBG, a protein that carries the hormone around the body.
Men in the highest quarter of animal protein intake had total testosterone about 1.2 nmol/l lower than men in the lowest quarter. Men in the top quarter for plant protein had levels about 1.1 nmol/l higher than those in the bottom quarter. SHBG showed similar patterns. Results were adjusted for age, body mass index and other dietary, lifestyle and health factors.
Does the type of protein matter?
The associations varied by source. Higher dairy protein intake went with lower total testosterone and lower SHBG. Meat protein was linked to lower SHBG but not to total testosterone. Protein from vegetables and other non-cereal plant sources was linked to higher total testosterone, according to the university's summary.
That is not a verdict on any food. The same release says the study cannot tell whether protein sources affect the body's production of testosterone, or its effects, and that other dietary or metabolic factors may explain the associations.
How much should anyone read into it?
Not much, according to the authors. Doctoral researcher Miika Wynne-Ellis says the differences were statistically significant but "relatively small", and that the study cannot establish whether they matter for health. The design is cross-sectional: diet and hormones were captured at one point, so there is no way to tell which came first. The men were Finnish, middle-aged and recorded between 1984 and 1989, a long time ago. Nothing here applies directly to women, to younger or older men or to people eating modern plant-based products.
Evidence that would settle the question is a randomised trial that swaps protein sources while holding everything else steady and measures hormones afterwards. That has not been reported here.
This is reporting on a study, not medical advice. Anyone concerned about low testosterone, or thinking of changing how they eat to alter hormone levels, should talk to a clinician or registered dietitian who knows their history, and should not stop or start prescribed treatment based on a single observational paper.
The more useful message for most readers is modest: protein sources are not interchangeable, and researchers are only beginning to ask what each does to hormones. The next step is whether other cohorts, with newer diets and women as well as men, show the same pattern.
Published in The Outspoken Digest
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Outspoken Digest Nutrition DeskDiet, food science and the evidence behind claims about what we eat.
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