Does milk increase or decrease testosterone?

There’s a lively debate about whether cow’s milk can increase or decrease your testosterone levels. What does the data tell us?

Are Frankencows messing with your testosterone?

Today’s genetically ‘improved’ cows produce milk throughout pregnancy, and their milk is high in estrogens and progesterone. Those hormones get into us when we drink the milk, so estrogen and progesterone blood levels are higher in milk drinkers.

You might be trying to increase or decrease your testosterone. You might be concerned about the effects on your kids. Either way, given that dairy products are a staple of most people’s diets, it’s important to know if this is something we should be concerned about.

It’s a frequent assumption on many online posts that the estrogen we consume in cow’s milk will decrease our testosterone levels. Is that true?

What do studies actually show us?

High-protein dairy drinks may boost testosterone, power and strength

A small study compared the effect of high-protein dairy milk on testosterone levels in two groups of young men after twelve weeks of resistance training. Those taking the high-protein dairy milk (250ml milk + 30g dairy protein after exercise and at bedtime) saw an increase in their testosterone levels compared to those taking isoenergetic carbs (maltodextrin). That said, testosterone increased in both groups, and the increase was tiny, so although the difference was statistically significant, that doesn’t mean it would have any noticeable effect on the body. The milk group also had a greater increase in weight (2 kg vs 0.8 kg) and in strength and power.

A similar study in Australian men and women over 50 also showed increased muscle power with high-protein dairy milk plus exercise but with no effect on testosterone levels.

In the very short term, milk protein may reduce testosterone

Curiously, testosterone levels fell in teenage boys immediately after drinking whey protein. However, the drop only lasted an hour and a similar fall was seen after drinking glucose. It’s unlikely this would have any significant effect on the body.

Long-term dairy intake may affect testosterone levels

Observational studies ask about long-term dietary habits and compare those against blood hormone levels. A couple of studies showed different results for men and women

A Taiwanese study in men found that a diet high in milk and dairy was associated with higher testosterone levels. The researchers estimated that differences in consumption of milk and other dairy products accounted for more than a quarter of the variation in testosterone levels between individuals.

Conversely, in another study, in premenopausal women, higher levels of dairy were associated with lower levels of testosterone and estrogen. Each daily portion of dairy decreased testosterone levels by a tiny 0.5% but lowered estrogen by 5%.

What does it all mean?

Whilst commercially produced milk does indeed contain significant amounts of estrogen, there’s no clear evidence that it has any clinically meaningful impact on human testosterone levels. More important are other considerations, such as the benefits of dairy protein if you’re trying to build muscle and the detrimental effects of full-fat dairy on cardiovascular risk. There is nothing to suggest you should have concerns about milk increasing or decreasing your testosterone levels.