Health and Medicine
PUBLISHED
In moderation, caffeine intake appears to have beneficial effects on health, but there’s a limit to almost everything. An overview of research in the area indicates that, for most people, five cups a day of coffee is safe, but high-caffeine energy drinks may be a different matter.
A popular parody of The Serenity Prayer reads: “Give me coffee to change the things I can and wine to accept the things I cannot.” Yet even the buyers of merch carrying these words may have a lurking fear as to the point at which coffee might not make the changes we want.
After all, some scientists attribute Honoré de Balzac’s death to his epic black coffee consumption.
Health researchers have long agreed that there is a “J-curve shaped” relationship between caffeine consumption and certain health concerns. That is, a cup of coffee or two a day is associated with reduced risk of things like type 2 diabetes, but at some point, the harm will outweigh the benefits.
However, working out where danger lies has been tremendously difficult. A new paper reviews the updated research.
Long-term nutritional studies are notoriously difficult because people aren’t always reliable recorders of what they consume. Moreover, there are so many confounding aspects to our diet – that disentangling represents a major problem.
“Food consumption, particularly meals high in fat or fiber, can delay the onset of caffeine and reduce the peak concentration in the blood,” a group chaired by Professor Gregory Marcus of the University of San Francisco, California, write in a review of published research.
Getting people to stick to diets for controlled trials is particularly challenging.
Despite all these obstacles, Marcus and co-authors think we can say that the safe limit for coffee might be a little higher than cautious previous reports have recommended.
“Caffeine consumed in coffee is a key part of daily life for millions of people, and in our review of the most recent research, for most adults, intake of up to 400 mg [milligrams] of caffeine/day, the equivalent of up to 5 cups of caffeinated coffee per day without added sugars or fillers, is safe and does not increase cardiovascular risk,” Marcus said in a statement.
That doesn’t rule out the theory that caffeine was the cause of Balzac’s demise, since he’s reputed to have drunk 50 cups a day to maintain his work rate.
Even Marcus’ estimate of five cups may be generous – five typically sized cups of particularly strong coffee would have up to double the 400 mg figure, although most brews are lower.
The authors say that caffeinated coffee may reduce insulin sensitivity, leading to a 27 percent reduction in type 2 diabetes in one large study.
Rates of heart disease, heart failure and stroke are lower in those that drink by 2-4 cups of caffeinated coffee a day. In moderation, these benefits outweigh harmful effects such as higher blood pressure, but it is possible to do even better.
For example, although unfiltered coffee has been found to raise LDL (bad) cholesterol, this appears to be caused by the molecule cafestol, which paper filters (or instant coffee if you must) remove.
Anyone hitting the coffee machine for an all-nighter doesn’t just need to be wary of crossing a line somewhere between five and 50 cups, however. There are long-standing concerns that energy drinks carry greater risks than more traditional caffeine-rich beverages, which the authors share.
“High doses of caffeine, such as those found in energy drinks including energy shots, may have harmful effects on the heart and should be avoided,” Marcus said. The authors note research showing commercially available drinks with three to four times the caffeine of coffee.
Others claim that while energy drinks are indeed harmful, it’s something in the way molecules interact, rather than any one ingredient.
One reason coffee appears to be better than other caffeine-rich drinks (tea aside) is that coffee contains plenty of compounds other than caffeine, and some of these are thought to have antioxidant and anti-inflammatory effects.
Although some research has looked at the effects of decaffeinated coffee, which could control for this, many experts consider these insufficient; studies on caffeinated coffee are much more abundant.
Sugar, milk, and other flavorings complicate matters further. Most can be expected to do some harm, but for those who enjoy them it’s seldom clear how the positive effects of the coffee and the negative consequences of additives stack up.
Moreover, the authors note that individuals don’t always fit the global average: “it’s important to remember that there is no ‘one-size-fits-all’ strategy for safe caffeine consumption. People can respond very differently to caffeine based on various factors, such as age, medications, underlying health conditions, genetics and how quickly their bodies metabolize it,” Marcus said.
Genetic studies that could predict personal responses are still in their infancy. In the meantime, Marcus noted, “What may be a reasonable amount for one person could cause unwanted effects, such as heart palpitations, anxiety or sleep disruption, in another.”
“That’s why it’s important to pay attention to how your body responds to caffeine and talk with your healthcare team about what is right for you.”
As just one example, the report does not overturn past warnings about coffee drinking during pregnancy.
The study is published in Circulation.
