Deep Dive


You have been taught that fiber is important. And fiber is important, but there is a little more to it than that. Dietary fiber consists of two types of indigestible carbohydrates: soluble and insoluble fiber. Resistant starch, the “third” fiber, is not technically a fiber but it plays a similar role to soluble fiber.

Fibers are not broken down by your digestive enzymes and reach your large intestine intact. Once there, your gut bacteria ferment some of the fibers (soluble fibers and resistant starch). The products of this fermentation are healthy fatty acids that can then enter your bloodstream. Soluble fiber and resistant starch are called prebiotics because they feed the good bacteria in your digestive system.

The other type of fiber, insoluble fiber, is not or only partly fermentable by your gut bacteria, and largely passes through your system untouched. This is the fiber that is prevalent in whole grains and which we have been taught to eat a lot of. The reasoning behind this is that insoluble fibers act like brooms that sweep out your intestines and keep you regular. But although that image gives us a soothing sense of hygiene, too much insoluble fiber may actually damage your intestines. If you have a healthy metabolism and stay away from refined foods, there’s absolutely no need to eat extra whole grains or beans to supplement your insoluble fiber intake.

In fact, it may be doing you more harm than good. Quite apart from the potential negative effects of eating too many insoluble fibers, the foods that are rich in those fibers have very little additional nutritional value to offer. And to achieve the amounts of fiber modern nutritional guidelines advise you to eat, you can’t just eat a slice of bread and a few beans in your salad. You’ll need to substitute entire meals with whole grains and beans. Meals where you could be eating other, more nutritious foods instead.

If you are unsure about ignoring official nutritional advice, consider leaving whole grains and beans out of your diet for just a few weeks. We predict that contrary to what you’ve been told, your gut health will actually improve, and you’ll become more regular and feel less bloated.

So, what are the best sources of healthy fiber? Basically, fruits and vegetables of all kinds provide fibers. Starchy fruits and vegetables like bananas, potatoes, sweet potatoes and yams are a good source of soluble fiber and resistant starch, while leafy vegetables are a good source of insoluble fiber. As long as you eat a good variety of fruits and vegetables, you will get enough dietary fiber. If you experience troubles with constipation or loose stools, try to eat more fruit and vegetables (especially leafy vegetables, root vegetables and pumpkin-like vegetables).