Spilling the Beans

Have you heard the latest news about coffee? It can be hard to keep straight on whether coffee is A, good for you; B, not so good; or C, it depends on who’s drinking it; D, all of the above; or E, none of the above.

It’s enough to make you run out and order a double-shot espresso.

In the interest of coffee drinkers everywhere, here are the latest thoughts from leading researchers about coffee and whether it can enhance—or not—our health. We are “spilling the beans” on who should and shouldn’t be drinking coffee, especially if you suffer from certain conditions.

Coffee and the Dehydration Myth

Scientists define coffee as a “mild diuretic.” Drink it, they say, and you will increase your urine output and likely multiply your number of daily bathroom runs.

Until recently, scientists also generally agreed that drinking coffee causes dehydration. This seems logical: By urinating more often and in greater volume, you’re draining the body of precious fluids, right?

Wrong, according to Lawrence Armstrong, a professor of exercise and environmental physiology at the University of Connecticut.

In 2005, Armstrong and his colleagues conducted an 11-day controlled study of 60 males to examine the body’s response to caffeine intake. For the study’s first six days, all 60 men ingested roughly 226 milligrams of caffeine (the equivalent of two cups of brewed coffee) each day. On the study’s seventh day, the scientists separated the participants into three different groups: Twenty men maintained their present caffeine intake, 20 men doubled their caffeine intake to about 452 milligrams of caffeine (about four cups of coffee) per day, and the remaining 20 men avoided all caffeine until the study’s conclusion. For every participant, researchers monitored 20 different indices of hydration, including variables in the body, blood and urine.

At the end of the experiment, all 60 men still had similar hydration variables, says Armstrong. The study’s results, published in the International Journal of Sports Nutrition and Exercise Metabolism, suggest that drinking moderate amounts of caffeine does not lead to dehydration.

As Armstrong explains it: “Caffeine creates a diuretic effect in the body, this is true. But a diuretic effect is not the same thing as whole body dehydration. What caffeine does is cause a brief increase in urine output followed by a decline.”

Imagine, the scientist says, that you drink a liter of water. In the period immediately following this feat, your urine output will increase and then eventually decline. “Does this mean you are dehydrated?” Armstrong asks.

The answer, of course, is no.

More research must be done to determine if high concentrations of caffeine or chronic coffee consumption leads to dehydration. But in the meantime, coffee drinkers, enjoy your java in moderation, and count each cup of coffee as roughly equivalent to the same amount of water.

Coffee’s Disturbance at Night and Naptime

Caffeinated coffee is a stimulant, and when consumed late in the day it can result in a very restless night of sleep. Studies have found that caffeine can reduce a person’s perceived quality of rest and their total minutes spent in slumber. It also can increase the number of times a person wakes throughout the night. Still, many people choose to drink coffee after dark in hopes of warding off fatigue during graveyard shifts, late nights out and overnight study sessions.

However, the scientific world recently discovered that the effects of caffeine disturb daytime sleep more than nocturnal sleep. If you’re a night owl hoping to recover your rest during daylight—good luck. According to researchers at the University of Montreal, you’ve already got two strikes against you.

In the 2006 study, published in the Journal of Neuropsychopharmacology, Canadian scientists divided 34 moderate caffeine consumers into two groups. Half of the participants followed their normal nocturnal sleep schedule, while the remaining participants altered their sleep patterns to stay awake during the night and then “recover” by sleeping the next morning. All participants consumed either a placebo or 200 milligrams of caffeine in the hours before “bedtime.”

Members of the caffeinated, recovery group slept for a shorter period of time and spent fewer minutes in deep sleep relative to the study’s other participants. Scientists liken this scenario to a biological one-two punch. Caffeine consumption shallows a person’s sleep, thereby making it increasingly difficult to ignore nature’s circadian alarm clock. The end result, it seems, is a relatively uneasy session of recovery sleep.