A huge European research project called ISAFRUIT is trying to figure out the science behind why fruits are good for us, and it goes way beyond vitamins and minerals. It turns out that eating apples — specifically apple pectin — encourages the growth of “good bacteria” in the guts.

Bacteria don’t just make us sick. Some bacteria are important to our digestive system. That’s why many people recommend eating yogurt after taking a series of antibiotics. The yogurt is thought to work as a “probiotic“, repopulating good bacteria and making the environment hospitable to other beneficial bacteria.

Unlike yogurt, apples don’t actually contain living bacterial cultures. However, “when apples are eaten regularly and over a prolonged period of time, these bacteria help produce short-chain fatty acids that provide ideal pH conditions for ensuring a beneficial balance of microorganisms. They also produce a chemical called butyrate, which is an important fuel for the cells of the intestinal wall.” That makes them a source of prebiotics.

There’s more! The bacteria this encourages not only contribute to good digestive health, they may also influence cancer risk.

Even though more research must be done to see if apples have the same effects on humans that they do on rats, apples are still low in calories, a good source of Vitamin C, and contain small amounts of many other vitamins and minerals. They even have a few milligrams of Omega-3 fatty acids, which may extend the life of cells. It’s certainly worth eating one a day.