Fiber - it’s a bit misunderstood. Conventional wisdom associates a high-fiber diet with going to the bathroom regularly, and not many other benefits. For many people, fiber is viewed as a “medicine” that gets things moving down there, usually a thick, granular solution like Metamucil or other fiber-based drink that’s tough to gag down.
So fiber suffers twice: not only do Americans avoid discussing bathroom problems as an “impolite” topic of conversation, but they also believe that fiber’s boring, or gross.
New research demonstrating fiber’s impact on multiple organ systems should convince you that fiber needs to be a daily nutritional presence in your diet, not just a substance that you turn to when things down there are...stuck.
The nitty gritty
Fiber is far more than just lettuce and psyllium husks. In fact, dietary fiber is a type of carbohydrate made up of sugar molecules linked together. Unlike other carbohydrates, dietary fiber is bound together in such a way that it cannot be easily digested in the small intestine. It travels to the large intestine to undergo partial or full fermentation and then is excreted, pushing everything else that has accumulated in our large intestine out with it.
Many people think that fiber is only helpful for constipation, but not for diarrhea. But fiber can be helpful for both, as it works to normalize the amount of water in the intestines. Cue the poop jokes here--they all apply!
There are three types of dietary fiber:
- Soluble dietary fiber dissolves in water to form a thick gel-like substance in the stomach.
- Insoluble fibers help hydrate and move waste through our intestines.
- Fermentable fiber feeds the good bacteria in your gut and can be either soluble or insoluble.
Current evidence shows most American adults only get a measly 16g of fiber per day, which is the recommended amount that a 4-8 year old child needs to stay healthy. We can do better.
So how much fiber do you actually need?
Adequate intake of fiber varies based on age and gender. This resource outlines recommended daily intake of dietary fiber by population. Men need more fiber than women, and growing adolescents and teens need a surprisingly high amount.
Adult Females, aged 19-50: 25 grams; Over age 50: 21 grams
Adult Males, aged 19 to 50: 38 grams; Over age 50: 30 grams
Teenagers, aged 14 to 18: 25.2–30.8 g
Adolescents, aged 9 to 13: 22.4–25.2 g
Children, aged 4 to 8: 16.8–19.6 g
Children, aged 1 to 3: 14 g
How does fiber work?
As fiber makes a round trip through our bodies, it plays an important role in our digestion and overall health. Fiber does a lot of work for a substance that we don’t even digest!
Our gut is a delicately balanced ecosystem, full of beneficial bacteria called probiotics as well as certain types of fiber, known as prebiotics. Fiber acts as a source of fuel for the beneficial microbes in the digestive system and helps remove the microbes that are not beneficial.
And when your gut microbiome is healthy, chances are the rest of your body is too: evidence confirms the gut plays a vital role in other bodily functions, including immunity, metabolism, and neurological function.
Beyond the bathroom
What happens when you don’t eat enough fiber? A low fiber diet has far-reaching effects that are more insidious than just constipation. Research suggests low fiber intake may be associated with a greater risk of inflammation and susceptibility to pathogens, which increases your risk of serious disease.
So what happens when the typical American diet, which relies heavily on processed, low fiber foods, gets a fiber-full makeover?
We will see benefits in the following areas:
- Lowers the risk of colon problems, including diverticular disease and hemorrhoids.
- Cardiac health
- Binds to fatty acids, which help the body lower LDL (bad) cholesterol.
- Reduces blood pressure and curbs inflammation.
- Keeps Type 2 diabetes in check by slowing sugar absorption and keeping blood sugar levels steady.
- The microbiome may play a role here as well. Research has shown that certain microbes in the digestive tract produce short-chain fatty acids (SCFAs). Butyrate, one type of SCFA, is associated with improved regulation of glucose. Dietary components such as fiber may benefit gut microbiota composition and, as a result, influence the production of SCFAs and an individual’s glucose response.
- Helps you feel fuller for longer—and helps you eat fewer calories. In fact, research shows that if you’re trying to lose weight, the amount of fiber you eat is directly linked to your chances of success.
- Protects against metabolic syndrome (also sometimes referred to as Syndrome X, metabolic dysregulation, or insulin resistance syndrome) which increases your likelihood of developing serious health conditions, including Type 2 diabetes, heart disease, and stroke.
Fiber can even protect against not-so-great diets. In one study, researchers gave the insoluble fiber inulin to mice who were eating unhealthy, high-fat, low-fiber diets. The diet had caused the mice to gain weight and develop metabolic syndrome. Adding inulin to their diet seemed to shield them from some of the negative effects of the unhealthy diet, including the increased risk of metabolic syndrome. While this study isn’t a prescription to eat whatever you like (as long as you chase it with some soluble fiber!) the results suggest that fiber’s effects on intestinal microbiota may benefit metabolic health.
Fiber is easy to find
Thankfully, fiber is everywhere. Aim to eat a wide variety of different types of fiber: vegetables, fruits, legumes, nuts, whole grains, and seeds. Since different foods contain different types of fiber, variety is important, and—bonus—the microbiome thrives on variety.
Some easy-to-incorporate high-fiber sources:
- Navy beans
- White beans
- Adzuki beans
- Split peas
- Pumpkin seeds
- Chia seeds
- Collard greens
The different flavors of fiber
Turns out there’s a fiber for almost every condition. But be careful: all fibers are not created equal, as you can see in this chart. Some fibers are artificially manufactured to be bulking agents and have less nutritional value than their more natural counterparts. Extra care should be taken if you have celiac disease or are gluten intolerant, as certain fibers could aggravate your digestive system.
|Types of Fiber||Soluble/Insoluble/Fermentable||Sources||Health Benefits|
|Cellulose, some hemicellulose||Insoluble, non-fermentable||Naturally found in nuts, whole wheat, whole grains, bran, seeds, edible brown rice, skins of produce.||"Nature's laxative": Reduces constipation, lowers risk of diverticulitis, can help with weight loss.|
|Inulin oligofructose||Soluble, fermentable||Extracted from onions and byproducts of sugar production from beets or chicory root. Added to processed foods to boost fiber.||May increase "good" bacteria in the gut and enhance immune function.|
|Lignin||Insoluble, non-fermentable||Found naturally in flax, rye, some vegetables.||Good for heart health and possibly immune function. Use with caution if you have celiac disease or are gluten intolerant.|
|Mucilage, beta-glucans||Soluble||Naturally found in oats, oat bran, beans, peas, barley, flaxseed, berries, soybeans, bananas, oranges, apples, carrots.||Helps lower bad LDL cholesterol, reduces risk of coronary heart disease and type 2 diabetes. Use with caution if you have celiac disease or are gluten intolerant.|
|Pectin and gums||Soluble (some pectins can be insoluble)||Naturally found in fruits, berries, and seeds. Also extracted from citrus peel and other plants to boost fiber in processed foods.||Slows the passage of food through the intestinal GI tract and helps lower blood cholesterol.|
|Polydextrose polyols||Soluble||Added to processed foods as a bulking agent and sugar substitute. Made from dextrose, sorbitol, and citric acid.||Adds bulk to stools, helping prevent constipation. May cause bloating or gas.|
|Psyllium||Soluble||Extracted from rushed seeds or husks of plantago ovata plant. Used in supplements, fiber drinks, and added to foods.||Helps lower cholesterol and prevent constipation.|
|Resistant starch||Soluble||Starch in plant cell walls naturally found in unripened bananas, oatmeal, and legumes. Also extracted and added to processed foods to boost fiber.||May help manage weight by increasing fullness. Helps control blood sugars. Also increases insulin sensitivity and may reduce the risk of diabetes.|
|Wheat dextrin||Soluble||Extracted from wheat starch, and widely used to add fiber in processed foods.||Helps lower cholesterol (LDL and total cholesterol), and may lower blood sugar and reduce risk for heart disease; more research is needed. Avoid if you have celiac disease or are gluten intolerant.|
The end is just the beginning
If you’re ready to start adding more fiber to your diet, be sure to take it slowly so you don’t experience gas, bloating, or intestinal discomfort. Add some extra plant foods to your diet, and be sure to also increase your water intake. Over time you’ll reap all the health benefits of a high-fiber diet, beyond just better bathroom trips, while adding more flavor and variety to your plate!
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