The review, which is the most exhaustive of its kind to date, was led by Esther Myers, specialist in systematic research reviews at the International Life Sciences Institute. Myers and her team, who are presenting the findings this week at the Experimental Biology conference in Chicago, looked at how different levels of caffeine affected people in the short and long term, taking special care to look for any adverse health effects in the cardiovascular, musculoskeletal, reproductive, or behavioral areas.
After going over more than 700 studies on the safety of ingesting caffeine at various levels, the team found plenty of evidence to suggest that 400 milligrams of caffeine, or four cups of coffee, is safe for healthy adults to ingest daily. It’s not going to make you any healthier, but it’s not doing any damage either. Pregnant women, on the other hand are better off with 300 milligrams or less, or three cups of joe. This 400 mg limit isn’t new, though. It’s been propagated by the FDA and the International Food Information Council since around 2003, when a smaller Health Canada review made the suggestion. Now, it seems safe to say that recommendation was right on the money.
What might happen if you drink more than that in a day? Myers’ team found evidence of links to depression and dysphoria (general dissatisfaction with life), as well as anxiety, hypertension, and even higher numbers of sperm with DNA damage in men. Having that fifth cup of coffee for the day on occasion isn’t completely unsafe if you’re healthy, says Myers, but it’s best not to make a habit of it. And if only one cup of coffee already has too much caffeine for you, maybe go with tea instead.