Study finds coffee linked to testosterone, body fat and metabolism, especially in men

943 words

NASHVILLE, Tenn. (WZTV) — If coffee is part of your daily routine, a new study suggests your morning cup may be associated with more than just helping you wake up.

Researchers in Finland found that people who drank more coffee tended to have lower body fat, more skeletal muscle and different metabolic markers than those who drank less coffee.

The study also found a notable difference in sex hormones among men: Higher coffee intake was associated with higher total testosterone and higher levels of sex hormone-binding globulin, or SHBG, but lower free testosterone.

But before coffee drinkers celebrate, researchers stress that the study does not prove coffee causes these changes.

What did researchers study?

The study, published in the European Journal of Nutrition, looked at 2,264 adults from the Northern Finland Birth Cohort 1966. Participants were 46 years old when their health information was collected in 2012.

Researchers divided participants into four groups based on their usual coffee intake:

No coffee
1-2 cups per day
3-4 cups per day
5 or more cups per day

Most participants drank coffee. Only 70 of the 2,264 participants reported drinking none.

Researchers examined participants' body composition, blood sugar and insulin measures, cholesterol and other metabolic markers, as well as sex hormones.

They also analyzed 164 different blood-based lipid and metabolic measures using nuclear magnetic resonance testing.

More coffee was associated with less body fat

One of the study's findings had nothing to do with testosterone.

People in the higher coffee-consumption groups tended to have:

Lower body-fat percentage
Lower total fat mass
Less visceral fat
More skeletal muscle mass

Interestingly, BMI was similar across the coffee groups.

That means the difference wasn't necessarily that heavier coffee drinkers weighed less. Instead, they tended to have a different body composition, with less fat and more muscle.

COFFEE NEWS | Love Dunkin'? Here's how Nashville drivers can win free coffee for a year

What about testosterone?

This is where the study gets more complicated.

Among men, researchers found that total testosterone generally increased as coffee consumption increased.

Men who drank moderate and high amounts of coffee had significantly higher total testosterone levels than men who did not drink coffee.

After researchers adjusted their analysis for factors including BMI, education, smoking, physical activity and alcohol use, the association remained.

For every additional cup of coffee per day, total testosterone was associated with an increase of about 0.29 nanomoles per liter.

But there was a catch.

Researchers also found higher coffee intake was associated with higher SHBG and lower free testosterone and free androgen index in men.

A cup of coffee is shown in this undated photo. A new study from researchers in Finland found higher habitual coffee consumption was associated with differences in testosterone, body composition and metabolic markers, particularly among men. (SBG File)

So does coffee actually raise testosterone?

Not necessarily.

Total testosterone and free testosterone aren't the same thing.

SHBG is a protein that binds to sex hormones in the blood. Because coffee consumption was associated with higher SHBG in this study, the increase in total testosterone did not translate into an increase in free testosterone.

In other words, the finding is more complicated than: Coffee = more testosterone.

Researchers describe it as a broader hormonal pattern that may be relevant to metabolic health.

Women showed a different pattern

The testosterone findings were not the same in women.

Researchers found higher coffee intake was associated with higher SHBG and lower free testosterone and free androgen index, but they did not find the same association with total or bioavailable testosterone seen in men.

The researchers therefore described the hormonal findings as sex-specific.

Coffee and blood sugar

The study also found a more favorable glucose-insulin profile among men who drank more coffee.

Higher coffee intake was associated with:

Lower fasting insulin
Lower insulin levels during glucose testing
Lower measures of insulin resistance
Higher insulin sensitivity

The researchers also found lower levels of several branched-chain amino acids, or BCAAs, in people who drank more coffee. These included leucine, isoleucine and valine.

BCAAs are involved in metabolism, and previous research has linked elevated levels with insulin resistance and other metabolic conditions. However, this study only found an association and did not show that coffee lowers BCAAs or prevents disease.

There's an important limitation

The biggest thing to know about the study is that it was cross-sectional.

Researchers looked at people's coffee habits and health measurements at a particular point in time.

That means they can identify relationships, but they cannot determine cause and effect.

For example, the study cannot prove that drinking more coffee caused someone to have less body fat or a different testosterone profile.

Researchers also relied on participants to report how much coffee they normally drank.

The study did not have detailed information about the exact cup size, brewing method, bean type or additions such as milk or sugar. It therefore also cannot tell us whether caffeine itself was responsible for the associations.

So, should you drink more coffee?

The study doesn't establish an ideal amount of coffee to drink.

Instead, researchers say the findings provide evidence of an association between habitual coffee consumption and a broader hormonal and metabolic profile.

They say long-term studies and controlled experiments are needed to determine whether coffee itself causes these changes and which compounds in coffee may be responsible.

For now, the takeaway is a little more nuanced than coffee boosts testosterone.

Researchers found that heavier coffee consumption was associated with several differences in hormones, body composition and metabolism, particularly among men, but the study does not prove that coffee caused those differences.