Dr. Toshi Is In! "Dietary Fiber"

Dear Dr. Toshi,

I heard that it's important to eat fiber. Can you explain what fiber is and how we get it?

One of the things that I've been really impressed with in this area is the fact that many people are avid gardeners and they're growing a great variety of wonderful vegetables! It turns out that this is a truly wonderful thing for our health!

Studies show that fewer than 3 out of 100 people of Americans get the recommended amount of dietary fiber. Dietary fiber is important because it helps prevent both constipation and diarrhea, maintain bowel health, lower bad cholesterol (LDL) and blood sugar level, decrease the risk of heart disease, so overall, it's associated with a healthier, longer life. It even helps control your hunger because it makes you feel full. Fiber is a carbohydrate. "Oh no," you might be thinking. You might have been told to decrease the amount of carbohydrates (carbs) you eat to have a healthier diet, but fiber is a "complex" carbohydrate that you should eat more of!

The Institute of Medicine recommends that people eat this much fiber every day: 38 grams for men age 50 or younger, 25 grams for women age 50 or younger, 30 grams for men age 51 or older, and 21 grams for women age 51 or older. The average American eats about 15 grams of fiber a day.

But it turns out that just eating the right number of grams of "fiber" isn't enough, according to Dr. Bulsiewicz, a gastroenterologist and the author of Fiber Fueled.

Fiber is part of the cellular structure of plants that we humans don't have. It's in fresh fruit, fresh vegetables, and other plants like legumes (such as beans, peas, and lentils). Some fiber goes right through the digestive system intact, without being digested. We also depend on the good bacteria we have in our intestines to help us digest some other fiber for our benefit! It turns out that this process is extremely important for our health. These friendly bacteria are called our "microbiota," and they require fiber to survive and become key players in our health.

There are about 300,000 different edible plants on Earth, and they have two basic types of fiber: soluble fiber and insoluble fiber. Most plants have of both types. Soluble fiber dissolves in water and turns the water into a thick gel. It helps lower cholesterol and glucose levels in the blood. There's a lot of soluble fiber in oatmeal, nuts, beans, lentils, blueberries, apples, citrus fruits, and barley, for example.

Insoluble fiber doesn't dissolve in water. Insoluble fiber increases stool bulkier and softer, so it can be helpful to people who have constipation or irregular stools. Whole-wheat flour, brown rice, carrots, cucumbers, tomatoes, nuts, cauliflower, and green beans are good sources of insoluble fiber. In general, the less processed, the better. (Whole-wheat flour and brown rice have much more fiber than white flour and white rice.)

You may think that there is no way you can figure out and eat the right kinds of fiber! But there's a very simple way you can increase your fiber intake for your health. As you might have guessed, the best sources of fiber aren't fiber pills or powders or medications you get at a drug store. The best sources of fiber are whole grains, fresh fruits (not fruit juice, which is actually mostly sugar water), fresh vegetables, legumes (beans, peas, and lentils), and nuts. The key is to have lots of variety and to have a good amount of all of these "plant foods" in your diet. Dr. Rob Knight, a professor at the University of California and one of the founders of the American Gut Project says, "The single greatest predictor of a healthy gut microbiome is the diversity of plants in one's diet." So rather than counting how many grams of fiber you get, you may simply want to eat more plants and lots of different kinds of plants in your everyday diet.

Dr. Toshiko (Toshi) Luckow, MD is a Family Medicine physician at the West River Health Services hospital and clinics.