Fiber on low fodmap diet

Those on the low FODMAP diet often limit their intake of fiber-rich foods.

There are some foods that are high in fiber and low in FODMAPs. This article teaches you how to eat enough fiber while continuing to follow a low FODMAP diet.


What is Fiber?

Fiber is a carbohydrate that cannot be broken down by the body.

It either passes through the digestive system unchanged (insoluble fiber), or is fermented by intestinal bacteria in the colon (soluble fiber).

Fiber is found in intact plant foods including fruits, vegetables, legumes, nuts, seeds and whole grains. It can also be isolated and added to processed foods and fiber supplements.

For those with irritable bowel syndrome (IBS) and other gastrointestinal disorders, increased fiber intake is a popular recommendation to help alleviate symptoms.  However, not all fiber is created equal and certain types of fiber are high in FODMAPs. Therefore, these foods may worsen digestive symptoms rather than improve them.

Summary: Fiber is an important part of any healthy diet and is often recommended to those with digestive concerns. Be mindful of the type of fiber consumed when on the low FODMAP diet.  


 How Much Fiber is Needed?

According to the current Dietary Guidelines for Americans, adult women should eat around 21-25 grams of fiber and men should eat around 30-38 grams of fiber per day.

An easy way to calculate your specific fiber needs is based on 14 grams of fiber per 1,000 calories. The more you eat, the more fiber you need!

Summary: It’s important to meet your daily needs even when on the low FODMAP diet to reap all the benefits of fiber.


Benefits of Fiber

Fiber offers a wide variety of  health benefits.

Feeding “Good” Bacteria

Certain types of fiber are fermentable, meaning they provide food for the bacteria in the gut.

If you follow a low FODMAP diet, you might think that fermentation is a bad thing, but fermentation is a normal and healthy part of digestion. Fermentation also produces a fatty acid called butyrate, which has a variety of potential health benefits including increased immune system defense and decreased inflammation (1).

Studies on the low FODMAP diet show it can lower the number of bacteria in the colon, including good bacteria. This is one of the reasons why the diet is only used temporarily and why it is essential to focus on your fiber intake while on it (2).

Regulating Bowel Movements

Fiber improves bowel regularity by adding bulk and softening stool.

Soluble fiber absorbs water and can help add bulk to loose stool. Insoluble fiber passes through the intestines intact and is fermented by intestinal bacteria. This process draws water into the intestines and can help relieve constipation.

Reducing Disease Risk

Studies show that fiber can help lower markers for cardiovascular disease including LDL (or “bad”) cholesterol, C-reactive protein (CRP), and blood pressure levels (3).

Water-soluble fibers such as beta-glucan found in oats and barley appear to have the greatest benefits (4).

Fiber may also help lower the risk of type 2 diabetes due in part to its ability to slow down the rate of glucose absorption. This helps lessen spikes in blood sugar and prevents weight gain (5,6).

Summary: Fiber is beneficial to gut health because it provides food for the good bacteria and helps regulate bowel movements. An adequate intake of fiber may also help reduce the risk of certain diseases. Unfortunately, those on the low FODMAP diet may not be getting enough of this important nutrient.


Fiber and the Low FODMAP diet

The low FODMAP diet tends to be lower in fiber because it excludes certain types of fruits, vegetables, whole grains, nuts, and legumes and eliminates foods with added prebiotic fibers.

While high in fiber, vegetables such as artichokes and cauliflower are off limits on the diet. High fiber fruits such as apples and mango are also excluded.

Whole wheat is a good source of fiber, but should be avoided on the low FODMAP diet. This is because wheat contains fermentable carbohydrates called fructans.

Most legumes such as kidney beans and black beans are excluded from the low FODMAP diet due to the presence of a type of prebiotic fiber called galacto-oligosaccharides (GOS).

Prebiotics

Prebiotics are fibers that feed bacteria to keep them healthy and happy.

Often, prebiotics are also added to packaged foods to increase the fiber content. Three high FODMAP prebiotic examples are inulin, chicory root extract (or chicory root fiber), and fructo-oligosaccharides (FOS).

These fibers are often added to yogurt, protein bars, and breads. While following the low FODMAP diet, check products labeled “added fiber”, “good source of fiber”, and “high fiber”, to find out the fiber source.

Summary: Many foods that are high in fiber are also high in FODMAPs. High FODMAP fiber sources can also be hiding in packaged foods.


High Fiber Foods to Add to a Low FODMAP Diet

While it might seem like many high fiber foods are off limits, there are some foods that are allowed.

High fiber foods to add to a low FODMAP diet:

  • Grains: 

    • While certain grains should be avoided on the low FODMAP diet, other grains such as oats, brown rice, and quinoa can be suitable high fiber replacements.
    • Oats are low FODMAP in servings up to ½ cup with 2 grams of fiber per serving. Enjoy a bowl of oatmeal with low FODMAP fruit on top for even more fiber!
  •  Nuts/Seeds:

    • Most nuts and seeds allowed on the low FODMAP diet are limited to a one handful serving (about 10-15 nuts).
    • A handful of nuts can be an easy, fiber-filled snack when you are on the go, but you can also get a little fancier with your fiber! With nine grams of fiber per two tablespoon serving, chia seeds are a fantastic way to add fiber to a low FODMAP meal or snack. Get your chia seed fix with these delicious Low FODMAP Granola Muffins!
  •  Fruits:

    • Were you part of the “apple a day” club before starting the low FODMAP diet? While you will need to kick your apple habit for now, replace apples with other high fiber fruits such as oranges, strawberries, and (unripe) bananas.
    • A good way to increase your fiber intake from fruits is to eat the skin. Canned fruit typically does not contain skin, but can still be a good source of fiber. Just be sure to look out for added high fructose corn syrup because excess fructose is not allowed on the low FODMAP diet.
    • Frozen fruit is another great way to add fruit to your diet without having to worry about spoilage. Frozen fruit that is purchased frozen and properly stored can maintain its quality in the freezer for about 12 months.
    • It is important to note that fruit should be limited to one serving per meal. This means that for breakfast, you can either have one orange or one banana, but not both. A fruit serving is typically about ½ cup chopped or about the size of a tennis ball if the fruit is round.
  • Vegetables/Starches:

    • Vegetables such as kale, broccoli (1 cup), and spinach are packed with fiber and other nutrients, plus they’re low FODMAP.
    • Potatoes sometimes get a bad reputation, but a baked potato with skin is high in fiber, vitamin C, and potassium!
    • As described in the fruit section, vegetables can also be consumed frozen or canned. Watch out for added sauces or flavorings (i.e. garlic and onions) that can often be found in these varieties.
  • Beans/Legumes:

    • Many people with IBS tend to avoid beans and legumes altogether due to their notorious side effects.
    • However, 1 cup of edamame, 1/4 cup of canned chickpeas and 1/2 cup of canned lentils are fiber-filled options allowed on the low FODMAP diet.
    • Even though they are often lumped into the “nut category,” peanuts are actually a legume and allowed in servings up to 32 nuts. Two tablespoons (32 grams) of peanut butter is also low FODMAP.

Here is a helpful chart that you can use to make sure you are eating enough fiber while on the low FODMAP diet:

Low FODMAP Sources of Fiber
Food Serving Size* Grams of Fiber
Grains    
Rice bran 2 tablespoons 3.1
Oats, rolled ½ cup 4.1
Brown rice, cooked 1 cup 3.5
Quinoa, cooked 1 cup 5.2
Nuts/Seeds    
Chia seeds 2 tablespoons 7.9
Almonds 10 nuts (12 grams) 1.5
Flaxseeds 1 tablespoon 1.9
Pecans 10 nuts (20 grams) 1.9
Fruits    
Strawberries 10 medium (140 grams) 2.8
Raspberries 10 berries (45 grams) 2.9
Orange 1 medium 3.1
Banana, unripe only 1 medium 3.1
Vegetables/Starches    
Potato, whole with skin 1 medium 3
Spinach, raw 1 cup 0.7
Broccoli, raw, whole 1 cup 2.3
Kale, raw, chopped 1 cup 4.9
Beans/Legumes    
Lentils, canned ½ cup 7.8
Chickpeas, canned ¼ cup 2.4
Mung beans, sprouted 2/3 cup 1.2
Peanuts 32 nuts (28 grams) 2.4

*All serving sizes listed are considered low FODMAP

Sources: Monash University Low FODMAP Diet app (last accessed 9/24/17). For the most recent data, please refer to the app.

USDA Food Composition Database

To download this list, click here


 Conclusion:

The health benefits of a fiber-rich diet are well known.

Therefore, if you are on the low FODMAP diet, you need to your make your fiber choices carefully. This is because many high fiber foods are also high in FODMAPs and fibers such as chicory root, inulin, and FOS added to packaged foods are off limits.

If you want to add more fiber to your low FODMAP diet, aim to eat foods from the high fiber, low FODMAP list on a daily basis. Overall, eat a well-rounded, healthy diet with at least 5 servings of vegetables, 2 servings of fruits, nuts, seeds, whole grains, and legumes. 

by Katelyn Collins, RDN