This article is general information, not medical or nutrition advice. Needs differ between people. If you have a digestive condition, are managing a medical issue, or are thinking about big changes to your diet, check with a doctor or registered dietitian first.
What dietary fiber is
Dietary fiber is the part of plant foods that your body cannot fully digest. Instead of being broken down and absorbed like most nutrients, it moves through the digestive system largely intact, and some of it is fermented by bacteria in the large intestine. Fiber is found only in plant foods: fruit, vegetables, whole grains, beans, lentils, nuts and seeds. Meat, fish, eggs and dairy contain none.
Public health guidance in many countries suggests that most adults eat less fiber than recommended. Commonly cited targets for adults are in the range of roughly 25 to 35 grams a day depending on age and sex, but exact figures vary by country and guideline, so check the advice that applies to you.
Why people talk about it
Fiber is associated with several things, though associations are not guarantees and individual results differ.
- Regularity. Fiber adds bulk and helps hold water in stool, which many people find helps keep bowel movements comfortable and regular.
- Fullness. Foods rich in fiber often take longer to eat and digest, so many people find them more filling. That can make it easier to feel satisfied at a meal.
- Heart and blood sugar. Diets rich in high-fiber foods have been linked in research with better cholesterol and blood sugar patterns. Since these studies usually look at whole eating patterns, it is hard to credit fiber alone.
- Gut bacteria. Some fibers act as food for beneficial gut microbes. This is an active research area, and much is still being learned.
None of this means fiber will fix any particular health problem. It is one part of an overall balanced diet.
Soluble and insoluble fiber
You may see fiber described in two groups. Most plant foods contain both, in different proportions.
Soluble fiber
Soluble fiber dissolves in water and forms a gel-like substance in the gut. It is often associated with slower digestion and with effects on cholesterol and blood sugar. Common sources include:
- oats and barley
- beans, peas and lentils
- apples, citrus fruit, pears and berries
- carrots and sweet potatoes
- psyllium husk and chia or flax seeds
Insoluble fiber
Insoluble fiber does not dissolve. It adds bulk and helps food move through the digestive tract. Common sources include:
- wheat bran and other whole grains
- the skins of fruit and vegetables
- nuts and seeds
- cauliflower, green beans and leafy greens
You do not need to count each type. Eating a variety of plant foods will usually cover both.
Where to find it in everyday food
Here are some practical examples of foods that tend to be good fiber sources.
| Food group | Examples |
|---|---|
| Beans and lentils | Black beans, chickpeas, lentils, split peas |
| Whole grains | Oatmeal, brown rice, whole-wheat bread, popcorn, barley |
| Fruit | Raspberries, pears with skin, apples with skin, oranges, prunes |
| Vegetables | Broccoli, Brussels sprouts, carrots, peas, artichokes |
| Nuts and seeds | Almonds, chia seeds, flaxseed, sunflower seeds |
Exact amounts vary by variety and preparation, so the nutrition facts label on packaged food is the best guide to what you are getting. If you are unsure what counts, the guide to whole grains can help you tell a truly whole-grain product from one that only looks it. Frozen produce and canned beans (rinsed, if you want less sodium) are convenient options and still provide fiber.
Easy ways to add more
Small, repeated changes usually work better than a dramatic overhaul.
- Start the day with fiber. Oatmeal with fruit or a whole-grain cereal is an easy option among quick breakfasts.
- Keep the skins on apples, pears, potatoes and cucumbers, when you like them that way.
- Add beans or lentils to soups, salads, tacos or pasta sauces.
- Choose whole-grain versions of bread, pasta or rice some of the time.
- Snack on fruit, raw vegetables, nuts or popcorn. Several healthy snacks double as fiber sources.
- Aim for variety. A mix of plants across the week tends to be better than relying on one source.
A balanced plate with half vegetables and fruit, a portion of whole grains and some beans or other protein sources is one practical way to build fiber into ordinary meals without counting grams.
Go gradually and drink fluids
If you suddenly increase fiber, you may notice gas, bloating, cramping or changes in bowel habits. Many people find that adding a little more every few days and drinking water throughout the day lets the body adjust. Fiber works best with enough fluid, as insufficient fluid can make constipation worse.
Some people, including those with certain digestive conditions, find that specific high-fiber foods cause problems. If you have persistent discomfort, unexplained changes in bowel habits, blood in your stool or unintentional weight loss, please see a doctor rather than adjusting your diet on your own.
Fiber supplements
Fiber is also sold in powders, capsules and gummies. Food sources come first, because they also provide vitamins, minerals and other nutrients. If you are considering a supplement, talk with a doctor or pharmacist, since fiber supplements can affect how some medications are absorbed and may not suit everyone. This article does not recommend any product or amount.
A realistic takeaway
You do not need to be perfect. Think of fiber as one reason to include more plant foods in the meals you already eat. Add one new fiber-rich food this week, see how you feel, and build from there at a pace that suits your digestion.