It may take more than an apple a day to keep the doctor away, at least when it comes to gastrointestinal health.

Nearly 70 million Americans are affected by digestive ailments such as gastroesophageal reflux disease or irritable bowel syndrome. Many factors can affect GI health, including stress, genetics and diet. A research team at the University of California, Los Angeles has found that people who have early life stress are more likely to develop irritable bowel syndrome, but the risk went down when they confided in someone they trust about their stress.

The take-away from the research, they said, is that people need to find healthy ways to manage stress. The GI tract functions better when people get into a routine that includes the right amount of sleep, exercise, a healthy diet and smaller, more-frequent meals.

Most Americans don’t eat enough fiber, the researchers say. To avoid constipation, you should add more fiber, but do so gradually — otherwise you might get gas and bloating and you won’t stick with the changes. They recommend at least 20 to 30 grams of fiber each day. Look for a variety of fruits, vegetables, whole grains and nuts. One bonus is that filling up on these goodies leaves less room for unhealthy choices.

Probiotics, or “good bacteria,” play a key role in the management of microbes in the GI tract. Yogurt contains probiotics, but researchers still don’t know what types of probiotics are best or how much should be consumed to make the gut healthy.

The researchers recommend working with a physician who can help you craft a plan to keep your gut healthy — one that you will actually want to follow.