Testosterone is the primary male sex hormone and is important for muscle mass, bone density, libido, energy levels, and more. Some claim that drinking milk and other dairy products can lower testosterone levels in men due to the presence of estrogen metabolites and DHT inhibitors found in dairy. However, the evidence on whether milk consumption actually decreases testosterone in men is mixed. This article will examine the current research on milk and testosterone levels and provide a conclusion on whether drinking milk lowers testosterone.
Does Dairy Contain Estrogen?
Bovine milk (cow’s milk) contains actual estrogen hormones like estrone sulfate and 17β-estradiol, as well as progesterone. This is because dairy cows are usually pregnant and lactating when producing milk, which leads to higher levels of these hormones. However, the amount of estrogen found in commercial cow’s milk is very low – one study found total estrogen levels ranging from 0.59 – 11.3 pg/mL. For reference, a woman’s body naturally produces around 50-400 pg/mL of estrogen. So while present, the levels of estrogen in dairy milk are minuscule compared to physiological estrogen concentrations.
Some dairy products like butter and cheese contain more concentrated estrogen metabolites due to processing methods like ultrafiltration. Buttermilk was found to contain 106 pg/mL, butter 102 pg/mL, and cheese up to 659 pg/mL of estrogen metabolites in one analysis. So while full-fat dairy like cheese and butter contain more estrogen than skim milk, the amounts are still very low.
There is also no evidence that the tiny amount of estrogen metabolites in dairy products get absorbed into the bloodstream or have any biological effects in humans. One study had men consume 1 liter of commercial bovine milk daily for 60 days and found no changes in their serum estrogen levels.
So in summary – while dairy does naturally contain actual estrogen hormones due to cows being lactating and pregnant – the levels are extremely low and likely have negligible effects if any on estrogen levels when consumed.
Does Dairy Contain DHT Inhibitors?
Some claim that dairy may lower testosterone by inhibiting 5-alpha reductase, the enzyme that converts testosterone into the more potent androgen dihydrotestosterone (DHT). DHT is considered even more important for libido and sexual function.
Two compounds found in dairy – linoleic acid and oleic acid – have been found to inhibit 5-alpha reductase in vitro and block the conversion of testosterone into DHT. However, the concentration needed to exert this effect was extremely high at 100 μg/mL – far beyond normal physiological levels.
One human study did find that men consuming 3-5 servings of full-fat dairy daily for 8 weeks showed an increase in testosterone but a decrease in DHT compared to men eating a low-dairy diet. The researchers speculated this may be due to DHT suppression from the fats in dairy. However, this study did not measure the mechanism directly so it’s not conclusive dairy was inhibiting 5-AR.
Overall current evidence does not strongly support the idea that reasonable intakes of dairy significantly inhibit 5-alpha reductase or reduce DHT levels. But more research is still needed on this potential mechanism.
Does Dairy Increase Sex Hormone Binding Globulin?
Sex hormone binding globulin (SHBG) is a protein that binds to testosterone in the blood and makes it unavailable for use in tissues. So higher SHBG levels are associated with lower free and bioavailable testosterone.
Some dairy compounds like the milk protein casein have been found in cell and animal studies to increase liver production of SHBG, which could potentially lower testosterone over time. One study found giving casein protein to male rats decreased testosterone compared to soy protein.
However, current evidence does not show dairy consumption meaningfully affects SHBG levels in humans. One study had young men consume low or high dairy diets for 8 weeks. While the high dairy group showed a small 2.7% increase in SHBG, it was not statistically significant.
Overall, there is limited evidence at this point that reasonable dairy intakes can impact SHBG levels enough to influence free testosterone levels in men. But more high-quality clinical studies are still needed.
Does Dairy Increase Estrogen Excretion?
While the estrogen content in dairy itself is low, emerging research shows dairy may indirectly increase estrogen excretion from the body.
One study had men take whey protein isolate. The whey protein led to increased urinary excretion of estradiol, a potent estrogen. The researchers speculated this may be due to whey binding to estradiol and increasing its elimination.
Another study found that feeding cow’s milk to rats increased the excretion of estrogen metabolites by 30-60% compared to controls. The milk again seemed to bind to estrogen in the gut and promote its elimination.
If confirmed in more human studies, this mechanism would suggest dairy may actually lower estrogen levels over time by increasing estrogen excretion. This is contrary to claims that the small amount of estrogen in dairy accumulates and increases estrogen activity.
Do Observational Studies Show Lower Testosterone?
Several large observational studies have associated higher dairy intake with lower androgen levels in men:
– One study on over 600 Danish men found that those consuming >200 mL milk daily had 15% lower total testosterone than those consuming 100 older Taiwanese men, those consuming >250 mL milk daily had 13% lower total and free testosterone than those consuming 100 male athletes found those consuming >200 mL milk daily had 32% lower free testosterone than those consuming Do Intervention Studies Show Lower Testosterone?
Several controlled trials have examined how increased dairy consumption affects testosterone levels over a set period of time:
– 20 young men were randomized to drink 710 mL of conventional or organic whole milk daily for 3 weeks. Total and free testosterone did not change in either group.
– 43 older men consumed either whey protein or carbohydrates twice a day for 12 weeks. The whey protein group increased total testosterone by 15% and free testosterone by 18% versus no change in the carbohydrate group.
– 24 middle-aged men consumed 500 mL of skim milk daily or did not change diet for 12 weeks. Total and free testosterone did not change in the milk drinkers compared to non-milk drinkers.
– 20 young physically active men consumed 500 mL of skim milk after resistance exercise on workout days or did not consume milk for 12 weeks. No differences were seen in testosterone levels between groups.
Overall, most controlled studies adding dairy to the diet have not shown decreases in total or free testosterone in men so far. A few have even shown increases, possibly due to added protein, calcium, or vitamin D.
Does Fat Content Matter?
Full-fat dairy products contain substantially more estrogen metabolites and androgen inhibitors like linoleic/oleic acid compared to low-fat dairy.
However, research has not found clear evidence that consuming full-fat dairy lowers testosterone compared to low-fat:
– One study had men switch from full-fat to low-fat dairy for 4 weeks. Total and free testosterone did not change.
– Another trial had overweight men eat low-fat cheese and fermented milk or avoid dairy for 12 weeks. No changes occurred in total or free testosterone.
– In the milk intervention studies above, full-fat, low-fat, and skim milk did not lower testosterone levels.
Overall, while full-fat dairy contains higher amounts of potential anti-androgens, evidence does not suggest it lowers testosterone substantially more than low-fat when consumed in normal amounts. But more research is still warranted.
Does Raw vs. Pasteurized Matter?
Raw (unpasteurized) milk retains more bioactive enzymes and hormones compared to pasteurized milk which eliminates pathogens through heat treatment.
But research has not found a difference between raw and pasteurized dairy in effects on testosterone:
– In one study, men drinking raw milk for 3 weeks did not show changes in testosterone versus pasteurized milk.
– Another trial compared whey protein made from raw milk to conventional whey. No differences occurred in effects on testosterone.
Overall there is currently no strong evidence that drinking raw dairy lowers testosterone compared to conventionally processed dairy products.
Does Organic vs Non-Organic Matter?
Organic dairy comes from cows not treated with hormones or antibiotics. Conventional dairy may contain slight residues from growth hormones like bovine somatotropin (bST) used to increase milk production in cows.
However, research again does not indicate a difference:
– One study compared organic milk to conventional milk in young men for 3 weeks. No differences occurred in effects on testosterone.
– Similarly, another trial found no differences in testosterone changes in men drinking organic versus conventional dairy for 14 days.
Current studies do not provide evidence that drinking organic dairy versus conventional impacts testosterone levels differently. Likely because growth hormone residues in conventional dairy are very low to begin with.
Does Milk Lower Testosterone in Bodybuilders?
Bodybuilders and serious athletes tend to consume substantially more protein, including milk-based proteins like whey and casein. This has raised concerns in the fitness community that dairy could impair their optimal testosterone levels.
However, most research in strength athletes and bodybuilders show either no effect or an increase – not a decrease – in testosterone from high dairy intake:
– Young male bodybuilders drinking 500 mL of skim milk daily for 12 weeks showed no change in testosterone versus a non-dairy control group.
– Elite female gymnasts consuming either dairy or soy protein for 4 weeks as 28% of total calories had no differences in testosterone.
– Male strength athletes taking whey protein for 12 weeks experienced a 17% increase in basal testosterone levels versus no change in carbohydrate controls.
The protein, nutrients, and hormones in dairy products could potentially counteract any anti-androgenic effects, explaining why many studies in athletes show neutral or beneficial effects on testosterone.
Conclusion
Based on a review of the current research, there is limited evidence that drinking milk significantly lowers testosterone levels in men. While dairy does naturally contain estrogenic compounds and potential anti-androgens, the amounts are low and likely have negligible biological effects in humans when consumed in normal amounts. Most well-controlled intervention studies adding dairy to men’s diets have not shown decreases in circulating testosterone. A few have even shown increases, possibly due to other hormones and nutrients counteracting any anti-androgenic effects. Differences in fat content, raw vs pasteurized, or organic vs conventional dairy do not seem to substantially alter these effects. Even in bodybuilders and athletes consuming higher amounts of dairy, most studies indicate neutral or beneficial effects on testosterone levels. More research is still needed on the mechanisms of action. But the current evidence does not support the idea that drinking milk in normal amounts meaningfully reduces testosterone in most men. As with any food, moderation is key. But there is no compelling reason to avoid dairy completely out of fear it will lower testosterone levels.