Caffeine Rush

Coffee has been through its highs and lows, from being reviled for its effects on circadian rhythms and cardiovascular health to being touted as good for teeth, digestion, and even depression. Science is now equipped to answer the question that has plagued and sustained college students and desk jockeys on a deadline for ages: Is there even such a thing as too much of a good thing? And how much coffee is too much?

That answer, if you’re curious, is yes, and 28.

In a study recently published in Mayo Clinic Proceedings, Dr. Junxiu Liu and his colleagues looked at the link between coffee and cardiovascular risks, and actually came up with a mathematical answer: 28. In a study of 43,727 people over 17 years, one of the largest longitudinal studies on this subject, they found that at least for people under 55 years of age, 28 cups of coffee per week marked the tipping point.

The researchers collected baseline data on fitness and caffeine habits in-person by using questionnaires as well as a medical examination. They did blood chemistry analyses both postprandial and fasting,tested blood pressure, anthropometry, blood pressure, and ECG, as well as physical exercise between 197 and 2002. Keep in mind, these 43,727 people were the healthy ones between the ages of 20 and 87, the researchers ruled out participants with a history of stroke, heart trouble, or even poor fitness levels. Over 17 years, they quantified the association between coffee consumption and the death of the 32% participants who died during the course of the study. They looked at general as well as cause-specific mortality and, surprisingly, found a positive link between excess coffee consumption and heart problems. And while striving to define what “excess” was, they figured out the magic number: 28 cups of 236 ml each week, or about 4 cups, nearly 1 litre of coffee, per day.

Both young men and women who were heavy coffee drinkers had a 56 percent increased mortality risk from all causes. Overweight men had an even higher risk of death if they exceeded the 28 cup threshold. People older than 55, however, were not affected by high coffee intake.

Why does this happen and why is it age specific? The researchers posit it’s actually because the good and bad effects of coffee can counterbalance each other. If you throw genetics into the mix, the combination can be potentially lethal. They suggest that the antioxidant and anti-inflammatory properties of coffee react with caffeine’s potential to stimulate epinephrine, increase blood pressure and homocysteine amino acid levels while it inhibits insulin activity can create an imbalance. While the study is remarkable because it went for 17 years, it has drawn some fire for not taking into account smoking habits during the period of coffee consumption. In fact, other recent studies have indicated that coffee drinkers who don’t smoke live longer than people who don’t drink coffee (or smoke). So, how much coffee is too much? The bottom line is that the spectrum of literature indicates that 2 or 3 cups really won’t kill you.

This piece originally appeared in Popular Science India. Reprinted with permission. Chhavi Sachdev reserves the right to be identified as its author.