by Tara Postnikoff
A: At the end of 2017, coffee grabbed the media spotlight once again as the result of an “umbrella review” about coffee consumption and health, published in the British Medical Journal. The author looked at the meta-analysis of both observational and interventional studies to look for associations between coffee consumption and positive health outcomes. The resulting media buzz was big, with headlines like this one in The Globe and Mail: “Drinking three cups of coffee per day tied to health benefits.”
Over the years, the reported health effects (both positive and negative) of consuming coffee have been inconsistent and study results can seem contradictory. We now know through the field of study called Nutrigenomics that caffeine metabolism has a genetic component. The CYP1A2 gene controls the rate at which caffeine is broken down in the body and it is this rate of breakdown that determines whether the consumption of coffee (and other caffeine-containing products) has harmful or protective benefits.
It turns out there are slow metabolizers and fast metabolizers, and the answer is in your genes. You can’t determine by “feel” if you’re a fast or slow metabolizer of caffeine; only the genetic test will reveal your status. It appears that it’s a fifty/fifty chance. Half of us are slow metabolizers, meaning that it can take eight to 10 hours for our caffeine level to drop by half. Slow metabolizers have a greater risk of high blood pressure and heart attacks when caffeine intake is high. People in this group should try to limit their intake of caffeine to 200 mg or half a cup of coffee per day. Those who are fast caffeine metabolizers actually have a lower risk of heart disease with moderate coffee consumption than those who consume no coffee at all.
Based on genetics, 50% of the population can safely consume up to four cups of coffee per day. Between one and four cups per day may provide health benefits such as decreased blood pressure and decreased risk of cardiovascular disease, possibly due to the polyphenols and other antioxidants found in coffee bean.
A warning to go along with these findings: just because coffee is safe to consume, that doesn’t give us carte blanche to consume a bottomless cup. Keep in mind that the size of the cup quoted in studies is six to eight ounces (177 to 237 mL), which is smaller than most cups at your local coffee shop. Adding sweeteners and high-fat dairy products every time is not a health-enhancing habit either. Even if you are one of the lucky ones who can see some health benefits from coffee, keep in mind that you could still experience negative side effects from caffeine, such as anxiety, irritability and insomnia. Furthermore, excessive coffee intake can increase your risk for low bone density and reduce your ability to absorb minerals such as iron or calcium.
Reference: 1. BMJ2017;359:j5024.
Tara is a Registered Nutritional Consultant, certified Personal Trainer and triathlon/running coach in Toronto. She is an avid distance runner and triathlete, and a regular guest speaker for Running Room training programs.