Coffee and good health, more than an association?
How do we know if a food is healthy? Some of it is plain common sense, so steeped in tradition that it hardly needs proof, but for less obvious food items it usually starts with an observation.
We noticed, for instance, that people who drink lots of soda tend to gain weight and have a higher incidence of several chronic diseases, or that people who take multi-vitamins tend to be healthier.
An observation is followed by careful study to verify that there is indeed an association between the observed exposure and an outcome. If the association actually exists, we try to find out what explains the connection, and to see if the association is a result of a cause and effect connection. In the case of soda and obesity link, it has been established that drinking soda actually drives obesity; with vitamins it turns out that taking vitamins is what healthy people that engage in various other beneficial habits – they also exercise, wear seatbelts and bike helmets – tend to do. The extra vitamins are just an association and not the cause of their superior health.
Most Americans drink coffee, and it was good news to hear that drinking coffee regularly is associated with lower risk of several chronic diseases, such as type 2 diabetes, heart disease, Parkinson’s and several types of cancer. This association has been seen in many studies, and a recent review of many meta-analysis concluded that (with the exception of certain conditions such as pregnancy and women with risk of fractures) coffee is “more likely to benefit health than harm.”
The ideal next step would have been to test coffee as an intervention in a double blind, long-term study, a study in which environmental, nutrition and lifestyle parameters would be controlled. This is, of course, very difficult and expensive to do.
So, is coffee really good for you?
When it comes to studying nutrition such studies are rarely feasible.
But there are other ways to move forward. Another method to examine a connection between two correlated findings is to see whether there’s a plausible mechanism that would make the exposure cause the outcome.
This is precisely what a new study, just published in the American Journal of Clinical Nutrition set out to do.
Chronic inflammation, insulin resistance and hormonal dysregulation are thought to be behind the development of many chronic diseases. The new study looks at biomarkers – measurable biological markers that are characteristic of biological processes and indicate particular diseases or physiological states. The researchers looked at 14 biomarkers found in blood, including some from the insulin family (C-peptide, insulin-like growth factor 1), at several sex hormones (testosterone, estradiol,) and at inflammation markers such as C-reactive protein and interleukin 6. These were studied in two very large cohorts of about 15,500 women and more than 7000 men whose coffee habits were known.
And the results: Coffee consumption was associated with favorable shifts in the levels of the biomarkers tested. There were lower levels of insulin markers – high insulin secretion markers are linked with several cancers. There were lower concentrations of inflammatory biomarkers. Estrogen levels were lower – high estrogen is associated with higher risk of breast, ovarian as well as prostate cancer – and higher levels of testosterone (testosterone can act against breast cancer cells).
This was true for the participants who drank caffeinated as well as decaf drinks.
Because besides caffeine, coffee contains very many substances, such as polyphenols, trace minerals and diterpenoids that are thought to affect health conditions.
Time for a coffee break?
If you love coffee the latest research about coffee and health is encouraging.
Drinking coffee used to come with a dose of worry. The reason for that is that older coffee studies did not account for confounding unhealthy behaviors such as smoking and inactivity, which used to be more common among heavy coffee drinkers. Newer, better studies are finding that coffee is actually associated with good health, and the mechanism of benefit is plausible. This study adds another layer of credibility and evidence.
That being said, coffee may not benefit all people: People who metabolize caffeine slowly may not find coffee helpful in the same way that people who metabolize it normally do. The reason the studies of coffee show conflicting results may be due to a genetic variability in the way people react to caffeine.
Coffee also isn’t for kids. Major health organizations, including the American Academy of Pediatrics, recommend that kids avoid caffeine in coffee and energy drinks altogether, at least until age 12. Pregnant women are advised to limit coffee to about 2 cups a day.
And when you think of coffee and health, a reminder: Coffee is in essence a calorie free, unsweetened drink. Coffee drinks with sugar, syrups and cream can become calorie bombs – these aren’t a healthy habit.