By Michelle Simon, ND, PhD
“Eat a high fiber diet” has become a nutritional mantra. But does fiber really do more than keep you regular? And how do you know if you are getting enough of it?
A growing body of research has uncovered that fiber is essential to the care and feeding of a healthy microbiome–the collection of bacteria in your intestines that influences everything from your metabolism and immune system to your moods and behavior. What’s more, fiber’s résumé of health benefits extends beyond regularity and weight management to prevention of diabetes and heart disease, blood sugar management and more.
Here’s everything you need to know about fiber, including what it is, where to find it, how much you need, and how it contributes to your health.
Three Types of Fiber
There are three distinct types of fiber, and each works differently in your body.
Insoluble fiber has a tough consistency and doesn’t dissolve in water or break down in the gut. It slows down the passage of food through your gut so the body can absorb nutrients effectively. Insoluble fiber helps you regulate appetite and can aid in weight control. You can find it in whole grains, nuts, and the skins and stalks of fruits and vegetables.
Soluble fiber has a softer and stickier consistency and dissolves in water. It binds to substances from the foods you eat–like sugar and fatty acids. Soluble fiber does break down in the digestive system and becomes an important source of food for the good bacteria in your gut, supporting your body’s natural probiotics. Top sources of soluble fiber include beans, peas, oats, barley, fruits and avocados.
Resistant starch is the third type of fiber, discovered in the 1980s by English researchers Englyst and Cummings. This fiber literally resists breakdown (or digestion) making its way directly through the small intestine to the colon, where, much like soluble fiber, it becomes food for your good bacteria and offers a variety of other health benefits. Sources of resistant starch include most types of beans, rolled oats, peas, unripe bananas, and potato starch.
Fiber Supports a Healthy Gut, Heart and Overall Health
A healthy, well-fed gut lining helps make for a healthy microbiome. That’s one reason that soluble fiber and resistant fiber are both often known as prebiotics; they feed the probiotics that live in your gut, keeping those essential “good bugs” alive and thriving.
The microbiome are the trillions of bacteria that reside in your gastrointestinal tract and work with your cells, organs and systems as one whole. They play a huge role as gate keepers to the flow of nutrients and information throughout the body. They have what we might refer to as intelligence, bringing information in from the food you eat and in turn providing information from the gastrointestinal tract to the rest of the body. This is a critical role. While an unhealthy microbiome can contribute to a range of health problems including chronic inflammation, inflammatory bowel disease and even obesity, a healthy microbiome can help prevent these same conditions, and may even help protect against colon cancer.
Additionally, fiber is an important ally in weight management. High-fiber foods take more time to chew and are bulky, so they fill you up quickly. That means you feel fuller on fewer calories. Numerous clinical studies have shown that increasing dietary fiber as part of a weight loss plan leads to more significant weight loss.
Fiber also helps slow the absorption of sugar. When you eat sugary foods, the body has to produce the hormone insulin to help process the sugar. Frequent high insulin production can put you at risk of diabetes. Soluble fiber can help regulate blood sugar levels by binding to sugar and slowing its absorption into the bloodstream, decreasing the body’s demands for insulin. A study in the New England Journal of Medicine found that a diet with 50 grams of fiber benefited people with type 2 diabetes in a number of ways, including by lowering insulin levels. In fact, in recent years the recommendation of a high fiber diet has become a more standard part of diabetes management.
Another important benefit of fiber is its ability to stave off heart disease. Soluble fiber binds with fatty acids, helping to flush them out of the body and lower LDL (bad) cholesterol. LDL can line the walls of arteries and narrow them, leading to increased risk of heart disease and strokes.
The Right Amount and Sources of Fiber
Most Americans currently get a paltry amount of fiber in their diets, estimated at around 17 grams a day. That’s not nearly enough. Current recommendations from major health organizations range from 25 to 38 grams a day (depending on age and sex). That amount would be equivalent to one bunch of asparagus, an organic apple, half a cup of raw almonds, and one cup of either oatmeal or brown rice.
When increasing the amount of fiber in your diet it is important to go slowly. Sudden increases will overwhelm the capacity of your microbiome to properly digest the fiber which can result in gas, bloating and diarrhea. Slow increases allow the good bacteria in your microbiome to multiply, increasing your digestive capacity. Also, excess fiber has the potential to increase or decrease absorption of certain minerals like iron, zinc, magnesium and calcium, depending on the type of fiber.
Choosing whole foods that are high in fiber is superior to choosing “added fiber” foods. Added fiber is often manufactured, or stripped from the original plant sources. Because of this, manufactured fiber lacks the vitamins and minerals found in the original food sources of the fiber.
The benefits of fiber go far beyond regularity and digestive health, so make sure you are incorporating enough of all three types from high quality sources into your diet.
Michelle Simon is a licensed naturopathic doctor based in Seattle, WA, who has been practicing for 15 years. She also holds a PhD in Biomedical Engineering from the University of North Carolina at Chapel Hill. Michelle is Chairman of the Board at the Institute for Natural Medicine.