People who regularly drink more coffee may have less total and visceral fat and at the same time more muscle mass, according to the results of a new Finnish study. In men, higher coffee consumption was also associated with testosterone levels and more favorable indicators of glucose and insulin metabolism.
The study was published in the European Journal of Nutrition. The scientists used the data of the large-scale project Northern Finland Birth Cohort 1966, the participants of which are observed from birth. The analysis included 2,264 people aged 46.
Participants were divided depending on their usual coffee consumption. 70 people practically did not drink coffee, 296 drank one or two cups a day, 822 - three or four cups, another 1,076 participants - five or more cups daily.
The researchers discovered an interesting pattern: the body mass index in different groups did not differ significantly, but the body composition was different.
Participants who drank more coffee, on average, had a smaller body fat percentage, lower total fat mass, and visceral fat area. At the same time, they had a higher skeletal muscle mass. Differences in body composition were observed in both men and women.
"This study is interesting primarily because it shows the limitations of the usual BMI indicator. Two people can have almost the same body mass index, but a completely different ratio of fat and muscle tissue. In the Finnish sample, it was body composition, and not BMI, that was associated with the level of coffee consumption," says Svyatoslav Morozov-Leonov, Doctor of Biological Sciences, head of the Experts Club analytical center.
Scientists studied hormonal indicators separately. In men, each additional cup of coffee per day was statistically associated with an increase of approximately 0.29 nmol/L in total testosterone and approximately 0.08 nmol/L in bioavailable testosterone. The level of sex hormone-binding globulin, SHBG, also increased. These associations persisted after statistical adjustment for BMI, education, smoking, physical activity, and alcohol use.
However, the hormonal findings were much more complex than the phrase ``coffee increases testosterone'' might suggest.
At the same time as higher total and bioavailable testosterone in men, higher coffee consumption was associated with lower free testosterone and a lower free androgen index. In women, the researchers did not find a statistically significant relationship between the amount of coffee and total or bioavailable testosterone. At the same time, they also had higher SHBG and lower levels of free androgens.
"Therefore, it would be wrong to conclude from the study that five cups of coffee a day increases testosterone in men. The hormonal picture is much more complicated: total testosterone increased, but free testosterone decreased at the same time. The authors themselves are talking about a specific hormonal profile, and not about the proven stimulating effect of coffee," emphasized Morozov-Leonov.
Another interesting result is related to metabolism.
In men with higher coffee consumption, the researchers found a more favorable profile of glucose and insulin indicators. In representatives of both sexes, coffee consumption was also inversely correlated with the blood concentration of branched-chain amino acids — BCAA.
Elevated BCAA concentrations in a number of previous studies were associated with insulin resistance and an increased risk of metabolic disorders. The authors of the Finnish paper believe that the detected changes can help to better understand the relationship between coffee consumption and metabolic health observed in other studies.
At the same time, the scientists specifically warn that the results do not prove a cause-and-effect relationship.
The study was cross-sectional: coffee consumption, body composition, hormones, and metabolic indicators were assessed in one period of time. Therefore, it is not possible to determine whether it was coffee that led to the differences found, or whether people with a certain lifestyle and metabolic profile simply drank more coffee.
Furthermore, the amount of coffee consumed was self-reported by participants, and the group of people who did not drink coffee at all was small, with only 70 people out of 2,264. The Finnish population is also relatively homogeneous, so the results cannot be automatically generalized to other populations. countries.
“This is a good example of how nutrition research should be read. An association between a product and a certain health indicator does not mean that the product is the cause of the effect. Prospective studies and, most importantly, randomized controlled trials are needed for practical recommendations," says Experts Club representative Morozov-Leonov.
The authors of the paper also do not recommend increasing coffee consumption based on the results obtained. They point to the need for further research, including interventional studies in humans, to determine whether there is a causal relationship and which biologically active components of coffee may be responsible for the associations found.
Coffee contains more than a thousand different compounds, so the potential mechanism of action remains uncertain. Researchers consider hormonal and metabolic changes as one of the possible directions for further study of the effects of coffee on health.
"The most interesting result of the work is not the statement "the more coffee, the better." The research shows a much more complex relationship between habitual diet, body composition, hormones and metabolism. It is the verification of these mechanisms in long-term and controlled studies that should be the next stage," summarized Svyatoslav Morozov-Leonov.
Research Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland Birth Cohort 1966 study. The analysis included 2,264 participants of the Northern Finland Birth Cohort 1966. The authors declare no conflict of interest.
