Herman Melville, author of "Moby-Dick," said: "We cannot live only for ourselves. A thousand fibers connect us with our fellow men."

That’s a wonderfully true observation. But these days, with what we know about nutrition, he might have said: "A thousand fibers connect us with our fellow humans — and the trillions of microbes that inhabit our guts."

We've long known that if you're overweight or obese, your diet (fueled by sugars, unhealthy fats, and highly processed foods) damages your heart and raises your risk for cancer, diabetes, and other chronic diseases.

Studies have also found that in overweight people, those food choices mess with your guts, making you more vulnerable to gut-based bacterial infections like from E. coli and inflammatory bowel diseases like Crohn's.

But according to a new lab study in the American Journal of Physiology-Endocrinology and Metabolism, it isn't being obese that makes it harder for you to resist bacterial infections in your intestinal tract. The problem is a lack of fiber, whether you're overweight or not.

To protect your innards from outside invaders and inside troublemakers, get a daily dose of fiber from 100% whole grains, vegetables, fruits, and legumes. Aim for 25 grams of fiber daily for women and 38 grams for men — slightly less for those over age 50, according to the U.S. Department of Agriculture.

For instance, that could mean unsweetened oatmeal with fruit for breakfast; a hearty salad with chickpeas, a variety of veggies, plus lean protein for lunch; and roasted veggies, quinoa, and a salmon burger for dinner.

You'll live longer and healthier.