Are you getting enough fiber? Even if you consume enough total fiber, there are various types of fiber that each offer different benefits. If you are on a special diet, you may be missing out on one or more of the types.
Fiber is a carbohydrate and not an essential nutrient. It has no Recommended Daily Allowance (RDA), though there is an Adequate Intake level (AI). Some people, such as those on complete nutrition through an IV, live entirely without dietary fiber.
But just because you can technically live without fiber, should you? If you have a choice, it is better to include as much of this beneficial dietary component as you (comfortably) can. Though “superfood” tends to be a meaningless marketing term, fiber is a genuinely super part of many healthy foods.
We’re going to delve into all things fiber in today’s article. Here are the questions that we’ll answer:
- What exactly is fiber, and what are the different types of fiber?
- How much fiber should you get in a day?
- Is it possible to get too much fiber?
- What are the benefits of the different types of fiber?
- What are some of the best ways to increase dietary fiber in the diet?
Knowing the types of fiber is the first step in making sure you are getting enough
Wondering what “counts” toward your fiber intake? Both the dietary fiber that is naturally present in foods and the synthetic fiber that has been shown to benefit health counts. Animal-based foods lack fiber; plant-based foods are the best natural sources of fiber in the diet.
The Institute of Medicine (IOM) defines fiber as “nondigestible carbohydrates and lignin that are intrinsic and intact in plants.” Functional fiber is “isolated nondigestible carbohydrates that have beneficial physiological effects in humans.” Basically, sometimes, fiber naturally occurs in foods, and sometimes it is added to foods.
There is some scientific debate around how different types of fiber should be classified. Most discussions group fiber into soluble and insoluble categories, which the FDA defines as the following:
- Soluble fiber: forms a gel in the stomach after dissolving in water. Soluble fiber provides some calories since it is broken down by the bacteria in your large intestine.
- Insoluble fiber: does not dissolve in water. Insoluble fiber does not provide calories because it passes through your digestive system relatively intact.
Many plant foods contain a combination of soluble and insoluble fiber, though they may be higher in one type than another.
Some fiber is fermentable, fermented by the good “gut bugs” that live in your large intestine. This process creates gases and short-chain fatty acids. Other types of fiber are non-fermentable.
The IOM suggests that classing fiber into fermentable and viscous groupings may better explain their beneficial roles in the body. The term “viscous fiber” is often used interchangeably with “soluble fiber,” but some soluble fibers (e.g., inulin) are not viscous. This means that they will not have the same properties as other fibers in this group.
Though fiber is a type of carbohydrate, it is not technically considered a nutrient. That said, it is often referred to as a nutrient due to the benefits we’ll cover below.
As I discussed in the introduction, fiber is not essential (i.e., a fiber deficiency has not been demonstrated). Babies aged 0-6 months have a diet completely devoid of fiber (by the IOM definition) if they are exclusively breastfed. Patients fed by total parenteral nutrition (TPN) are also living without fiber.
Getting the daily recommended amount of fiber puts you ahead of the pack
The Dietary Guidelines suggest that we aim for 14 grams of fiber for every 1,000 calories that we eat. That means that a person on a 2,000-calorie diet should try to get at least 28 grams of fiber. The Daily Value (DV) on the nutrition facts label calls for 25 grams of fiber per day.
There are also more specific Adequate Intake recommendations for fiber, set by gender and age group. The AI “is believed to cover the needs of all individuals in the group.” However, the lack of data makes it impossible to state a percentage of the healthy population that is covered by the AI.
For adult women, ages 19-50, the AI for fiber is 25 grams per day. Women ages 50 and older have an AI of 21 grams per day. The recommendations for pregnant and lactating women are 28 grams and 29 grams, respectively.
Adult men ages 19-50 have an AI for fiber of 38 grams per day. Men ages 50 and older should aim for 30 grams of fiber per day. The higher AIs for fiber for men relate to their higher calorie needs (on average), compared to women.
You can get too much of a good thing when it comes to fiber
There currently is no Tolerable Upper Intake Level (UL) set for fiber. “Serious chronic adverse effects have not been observed” in individuals with a high fiber intake as part of a healthy diet. As mentioned above, most adults are not getting enough fiber; consuming too much is not a concern for most people.
However, it is possible to experience some mild gastrointestinal distress with excessive fiber intake. This is particularly true when someone consumes large amounts of synthetic or isolated fiber. Sticking to fiber that is part of a natural food matrix tends to be self-limiting and is more difficult to over-consume.
Fiber-rich foods are often high in tannins, oxalates, and (or) phytates that decrease mineral absorption. Decreased mineral bioavailability is often cited as a potential downside to the excessive intake of fiber. Consuming a balanced diet that contains a variety of plant and animal-based foods can help to decrease this risk.
So how much fiber might be too much? Some sources recommend staying under 70 grams of fiber per day. Again, it would be challenging to consume that much fiber without having a very unbalanced diet or relying on supplements.
Choose a fiber-rich diet to keep your digestive health in check and reduce the risk of chronic disease
Here are some of fiber’s most well-known benefits:
- May improve constipation or diarrhea
- Helps maintain healthy blood sugar levels
- Helps reduce the risk of heart disease and other chronic nutrition-related diseases (including type 2 diabetes)
- Adds volume to meals for few calories, promoting satiety and healthy weight management
- Higher intakes may improve blood cholesterol levels (including lowering the “bad” LDL cholesterol)
The different types of fiber each play different roles in the body. For example, viscous fibers reduce the reabsorption of bile acid, which can improve blood cholesterol levels. This improvement of the lipid profile may lower heart disease risk.
Insoluble fibers (e.g., cellulose and lignan) do not appear to impact blood cholesterol levels. Those on ketogenic diets tend to consume lower levels of viscous fibers that can help reduce LDL cholesterol. Modifying the diet by adding more keto-friendly viscous fiber foods may help to mitigate this issue.
Many soluble fibers fall into the viscous category. Those following a ketogenic diet who have high LDL cholesterol should include more of the following in their meal plan. These are a few of the keto-friendly sources of soluble fiber:
- Psyllium husks (Note: it is extremely important to consume psyllium with plenty of fluid. Its high capacity to bind water can create a choking hazard.)
- Flax and chia seeds
- Raspberries and Strawberries
Another benefit of viscous fibers is that they slow the rate that your stomach empties. This helps to slow the digestion and absorption of blood glucose, helping to reduce blood sugar spikes. Viscous fiber may also help make your meals feel more satiating and reduce diarrhea.
The insoluble fibers play other beneficial roles in the body. They provide bulk, which also makes lower calorie meals feel more filling. They may also help to prevent or improve constipation.
Constipation is the most common GI complaint in the United States. Keep dietary fiber in mind if you are one of the many sufferers of this uncomfortable condition. Bran may be particularly helpful to you.
Follow these tips to get a fiber-packed power up
There are a number of ways to increase the amount of fiber that you get in your diet. Choose the methods that best fit your food preferences and dietary pattern. Here are some foods that are rich natural sources of fiber:
- Legumes such as navy beans, kidney beans, split peas, and lentils
- Globe artichokes
- Sweet potatoes
- Asian pears
- Whole wheat bread and pasta
- Raspberries and blackberries
- Prunes and figs
- Spinach Almonds
Aim to increase your consumption of fiber with natural food sources, not supplements. Skipping the fiber supplements may encourage you to better your diet quality with foods first. Foods provide an assortment of beneficial phytochemicals, vitamins, and minerals that you may miss out on with a supplement.
The FDA allows naturally occurring fiber in foods to be listed as dietary fiber on the food label. These intact fibers contained within their natural food matrix have been shown to be beneficial.
On the other hand, fiber added to foods is not necessarily listed on the label as dietary fiber. Isolated and synthetic fibers must show a “beneficial physiological effect on human health” to count as dietary fiber. Unlike intact fibers that are in food, fiber added to foods may not provide the same health benefits.
Opting for whole grains over refined grains as much as possible is one simple way to increase fiber intake. Fiber is (mostly) stripped from grains during the refining process. By choosing whole grains, you are keeping the fiber as well as other components that are not replaced with enrichment.
The Dietary Guidelines recommend making at least half of your grain choices whole grains. Choosing only whole grains is a perfectly healthy option if that does not feel too restrictive for you.
Eat the edible skins or peels of your fruits and vegetables whenever possible to get more fiber. This makes food preparation easier (no peeling the sweet potatoes!) and is better nutritionally. It is truly a double win for you.
Dried fruits provide a more substantial amount of fiber in a smaller volume. Because much of the water is removed, dried fruits are also a more concentrated source of calories. Unsweetened fresh or frozen fruits will be a better choice if you have a weight loss goal.
Choosing whole fruits and vegetables instead of juices is another simple switch that can aid in increasing fiber intake. Juice has had its fiber content stripped away and is easy to over-consume. By sticking to whole fruits and vegetables, you will up your fiber and help promote your healthy weight management.
Don’t forget, legumes, nuts, and seeds. Meat, seafood, eggs, and poultry are healthy, high-quality protein, but they lack fiber. Including some plant-based protein sources in your diet on occasion can help you to increase your fiber intake.
Rapidly increasing your fiber intake can be tough on your digestive system. Make your healthy change a more pleasant experience by increasing your intake of fiber slowly. Be sure to increase your fluid intake along with the fiber to decrease the risk of gastrointestinal distress.
Final thoughts about Health Benefits Of Fiber
Many dietary components are beneficial but not essential for life. Fiber is one of these important components of food that you don’t want to miss out on. No matter your nutritional lifestyle, make sure to include fiber-rich foods in your diet to reap the benefits.
With some special diets, you may be getting more of certain types of fiber, and minimal amounts of others. Focus on including a variety of foods that contain different types of fiber. This way, you can enjoy all of the benefits of fiber, no matter which dietary approach you follow.
What are some of your favorite fiber-rich foods? Get some new ideas for increasing your fiber intake over in the recipe section!
Summer is a registered dietitian located in Avon, Connecticut where she specializes in weight management, special diets, general nutrition, and avoidant/restrictive food intake disorder (ARFID). She is the developer and content creator behind the Summer Yule Nutrition website, where she shares evidence-based information on hot topics in food and nutrition.