Fiber Fundamentals

How many times has your doctor — or basically the entire internet — said you could benefit from eating more fiber? And how many times have you thought, “Okay, but what is fiber?” Don’t worry — we’ve all been there. This article will ease some of your fiber worries and get you up to speed on fiber basics, some of the latest research and a possible new definition for this important nutrient.

The Basics

Fiber is a carbohydrate found in plant foods like fruits, vegetables, beans and whole grains. Unlike other nutrients, fiber can’t be further broken down and absorbed by the body. Instead, it passes through the gastrointestinal tract undigested and reaches the intestines mostly intact. Most of fiber’s beneficial effects happen in the large intestine (also called the colon).

There are two main types of dietary fiber, insoluble and soluble. Soluble fiber is able to absorb water, like what happens when you make oatmeal, and is known for slowing digestion and helping the body absorb nutrients from foods. Insoluble fiber doesn’t dissolve in water and instead sticks around to keep things moving through the gastrointestinal tract. Soluble fiber is found in oatmeal, legumes and fruits like apples, berries and oranges. Nuts, seeds, fruits, vegetables and whole grains are all sources of insoluble fiber. Since they’re found naturally in foods, both soluble and insoluble fibers are considered to be “intact” fibers.

This probably isn’t the first time you’ve heard that fiber has several health benefits. Though it’s best known for its ability to relieve constipation, it does more than make you “regular.” Fiber is a key part of good gut and bowel health, which can promote adequate digestion and absorption of several nutrients. It may lower total and low-density lipoprotein (or LDL) cholesterol as part of a healthy diet, may lower risk for certain types of cancer, and can improve blood sugar control. Finally, fiber can help with weight control, as most fibrous foods are relatively nutrient dense and help keep you fuller for longer. It’s recommended that adult men and women eat 38g and 25g fiber per day, respectively.

Fiber Under Review

The health benefits of fiber are well established and many fiber-focused health claims have been approved by the Food and Drug Administration for food labeling. Over the past few years; however, other types of fibers, isolated or synthetic non-digestible fibers, have been included in foodsThese fibers are extracted from plants or are synthetically made and then added into foods. Products like snack bars, yogurt, and cereal are bumping up their fiber content thanks to these compounds, some of which might sound familiar (pea, potato, apple, and soy fiber), and some of which may not (xylooligosaccharides, anyone?).

So what’s left to debate? It all goes back to the FDA’s definition of fiber, which states that dietary fiber “includes certain naturally occurring fibers that are ‘intrinsic and intact’ in plants and added isolated or synthetic non-digestible soluble and insoluble carbohydrates that the FDA has determined have beneficial physiological effects to human health”. Currently, the FDA is reviewing 26 isolated and synthetic non-digestible carbohydrates to determine if they meet the “beneficial physiological effects” requirement, and guidance for industry was issued in February 2018. Seven isolated and synthetic fibers have already been approved to be counted as fiber on labeling and in the Nutrition Facts Panel, including beta-glucan soluble fiber, psyllium husk, cellulose, guar gum, pectin, locust bean gum and hydroxypropylmethylcellulose.

The Bottom Line

Though the definition of fiber and what constitutes as it on your nutrition label may be evolving, don’t let that scare you away from this key nutrient. We know for sure that fiber found in fruits, vegetables, legumes, nuts and seeds, boasts lots of health benefits, and these foods are also high in vitamins, minerals, and other healthful nutrients. It’s also clear that both soluble and insoluble fiber have a place in your diet, and isolated and synthetic fibers can fit in as well. We’ll have to wait to hear the verdict on the fibers under review, but you can be sure of one thing: A nutritious diet is composed of many different types of foods, and variety is the key to establishing a healthy relationship with food.

This blog post includes contributions from Allison Webster.