Do you start your day with a warm cuppa joe? Most Americans do. More than 80 percent of U.S. adults drink coffee every day. And the average person drinks just over two cups each day. That’s a lot of coffee! While most people think it tastes delicious and provides an energy boost, is it good for us?

CC0 Public Domain
Source: CC0 Public Domain

A group of public health, nutrition and medical researchers reviewed the evidence on caffeine consumption earlier last week. They published their results in journal Food and Chemical Toxicology.

Their paper includes data from more than 380 studies on the effects of caffeine in the human body published between 2001 and 2015. Their analysis measured the effects of caffeine in five areas: overdose and potential death, the cardiovascular system, bone density and calcium levels, behaviors and developmental and reproductive issues. Here’s what they found.

First a general guideline: The available evidence shows that—for healthy adults—consuming up to 400 mg a day of caffeine is not associated with health problems. For pregnant women, the evidence shows that up to 300 mg a day is healthy.

To provide some context, the largest brewed coffee (a venti) at Starbucks contains about 415 mg of caffeine. A shot of espresso contains 150 mg, and a cup of black tea contains about 55 mg.

The paper offered a lot of other details about caffeine consumption. First, even though up to 400 mg is safe for healthy adults, caffeine is a stimulant that does have effects on the body. Consuming caffeine does increase alertness. If consumed before bed, it can lead to difficulty sleeping.

Caffeine will also lead to a short-term rise in blood pressure. While the change is relatively small and will not harm most people, it may result in negative effects for individuals who are genetically predisposed to high blood pressure or heart problems.

For some people, consuming up to 400 mg a day of caffeine can also lead to anxiety, especially for people predisposed to anxious feelings. But the reviewers conclude that—because the data are inconsistent and people have different sensitivities—individuals should be aware of anxiety-effects and moderate their caffeine intake accordingly.

Lastly, the data did reveal some instances of caffeine overdose, but these were associated with caffeine capsules or powders containing as much caffeine as approximately 100 cups of coffee taken in a single dose. The authors suggest restricting the amount of caffeine included in a single package of these capsules and printing warnings about the dangers of caffeine powder.

All caveats aside, the evidence shows that a morning cup of coffee (or two, or three!) really is safe and healthy, and may even provide some benefits in alertness and cognitive function. Bottoms up!

References

Wikoff, Daniele, Brian T. Welsh, Rayetta Henderson, Gregory P. Brorby, Janice Britt, Esther Myers, Jeffrey Goldberger, Harris R. Lieberman, Charles O'brien, Jennifer Peck, Milton Tenenbein, Connie Weaver, Seneca Harvey, Jonathan Urban, and Candace Doepker. "Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children." Food and Chemical Toxicology (2017).

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