If you’re a caffeine fiend, you might know that first sip of coffee or tea in the morning feels so darn good. And for 88% of us is great for us as well (see #4 below). But there’s a lot about your favorite sunrise pick-me-up you might not know. Read on for a bouquet of surprises.

  1. Coffee can cause contractions along your large intestines. Drinking coffee doesn’t cause everyone to run for the toilet, but among those who are so moved, the effect is likely related to colon contractions. One 1990 study found that people who reported the urge to go to the bathroom after drinking coffee did indeed have more pressure in their colons and rectums after drinking 200ml of coffee. Interestingly, decaf coffee (which has a little bit of caffeine) produced an effect, too—though hot water did nada. The jury’s still out on exactly how much of this coffee effect is related to caffeine in particular.
  1. Darker roasts of coffee have less caffeine. This might seem counterintuitive, because darker roasts can have such a strong taste, but it’s true: the more roasted your beans, the less caf in the coffee. Each bean loses caffeine as it roasts, so dark-roasted coffee brewed by volume has less caffeine than lighter roasts. (That said, roasting also shrinks beans, so dark coffee brewed by weight could actually have more caffeine.) Darker coffee is also easier on the stomach (not Dr. Mike’s though—he likes more caffeine and lighter roasts.) As coffee roasts, it creates a compound called N-methylpyridinium (NMP), which causes stomach cells to secrete less acid. The longer coffee roasts, the more NMP it creates, and the less acid your stomach cells secrete.
  1. Caffeine has the opposite effect on men under stress as on women. In one study, a group of college students drank either decaf or caffeinated coffee, then performed a series of stressful tasks. Women reported more confidence and outperformed men on collaborative tasks when they’d had caffeine. But for men, the reverse was true: they felt less confident after they’d imbibed, and did worse on stressful tasks. Did they not put whiskey in the men’s coffee and repeat the study? If they did so, they did not report that test in the journal in which this study was published.
  1. For about 88 percent of us in North America, caffeine has a strong health benefit. The more caffeine, the greater the age-reducing benefit. If you are a fast metabolizer of caffeine (a genetic trait that 88% of us have) , you do not have headaches, abnormal heart beats, anxiety, or gastric upset with 12 ounces of a usual strength cup of coffee, you gain more benefits from caffeine (with water or in coffee) the more you drink. If you are in the 12% of slow metabolizers, you get no health benefits from coffee. Caffeine for the 88% of us in North America that are fast metabolizers decreases Alzheimer’s, Parkinson’s and Type2 diabetes risk by more than 20% and the risk of 9 cancers too. So enjoy more of that joe!