You know fiber is good for you. You know you’re supposed to eat it, but what exactly is fiber? Why is it so important, and how much should you eat per day? We’re going to make this easy for you by laying out everything you need to know, including simple tips for increasing your fiber intake. (Spoiler alert: You have full permission to slowly increase your fiber intake. In fact, most experts recommend it since you may experience some not-too-pleasant side effects if you drastically increase your fiber intake in a short timeframe. That said, adding more fiber to your diet is much easier and tastier than you might think.)

What is fiber and why is it important?

Fiber is a complex carbohydrate that comes from foods like plant foods like fruits, vegetables, legumes, and whole grains, but unlike other carbohydrates, fiber can not be broken down or absorbed by the body. This means it moves through the body undigested.[1] That’s good for digestive health, because, let’s just say it helps move things along (more on that later).

But that’s not all. As Stanford University Associate Professor of microbiology and immunology Justin Sonnenburg says, “Fiber is more than a bulking agent.”[2] Certain types of fiber (more on that shortly) act as the fuel for the microbes that live in our gut. A study Sonnenburg conducted in 2016 suggests that consuming less fiber may mean fewer microbes in the gut.[3] Conversely, more fiber, more gut microbes, and better gut health.

There are two kinds of fiber: soluble fiber and insoluble fiber. Both are important.

Soluble Fiber

Soluble fiber is found in a range of foods, including oats, nuts, seeds, beans, lentils, apples and citrus. When it interacts with water, soluble fiber turns into a gel-like substance that moves through the stomach and small intestines slowly.[4] Why is this a good thing? Studies have shown that consuming soluble fiber can help lower glucose levels and cholesterol.[5]

Insoluble Fiber

Equally as important is insoluble fiber, which is found in foods like whole grains, legumes, most vegetables, fruits, nuts, and seeds. Insoluble fiber does not dissolve in water. Instead, it bulks up stool and aids in the movement of foods through the digestive tract. For those who experience constipation or irregular bowel movements, increasing intake of insoluble fiber can be an effective treatment.[5]

How much fiber do I need?

So, now that you know what fiber actually is, you want to know how much of it you actually need to consume, right?

The American Heart Association

According to the American Heart Association, adults need 25 to 30 grams of dietary fiber a day from food, not supplements. (Foods that are high in fiber have other nutrients and benefits, too, after all.) Unfortunately, most Americans are getting only 15 grams a day—about half the recommended amount.

The United States Department of Agriculture (USDA)

According to the United States Department of Agriculture (USDA), the government body that is responsible for establishing the nutritional guidelines and daily values you see on the nutrition labels of all your store-bought foods, recommends consuming 14 grams of fiber per 1,000 calories. At a 2,000 calorie reference level (which is appropriate for some but not all people) the daily dietary fiber intake should be 28 grams[4].

Tips for Increasing Fiber

It’s highly likely that you’re not eating enough fiber. In fact, national consumption surveys indicate that 95% of the U.S. population doesn't meet recommendations[5]. The average American consumes just 16 grams of fiber a day—well below expert recommendations[5]. 

Good news though: With the long list of foods that are high in fiber, it’s not only easy to increase your daily intake, but it can also be delicious. Here’s your game plan:

Increase fiber slowly

Take it slow (remember?). There’s no reason to jump into things too quickly, and in fact, slowly increasing fiber amounts will help your body adjust. You’ve probably heard people complain about feeling bloated or getting cramps after eating too much fiber. You don’t have to be one of those people! Everyone reacts to fiber differently. What may be too much too fast for someone might be the right amount for you. Play it safe and introduce fiber-rich foods slowly.

Spreading out your fiber intake throughout the day can also help reduce the risk of bloating and gastrointestinal discomfort from excess fiber. For example, choose oatmeal for breakfast, add some beans into your salad at lunch, and snack on some nuts later that day. As the week goes on, you can start adding more fiber to each of your meals. So a few days later, dress up your oatmeal with some berries and seeds, add another fiber-rich vegetable to that salad, and so on.

Drink water

Another major factor in doing this right: Drink water and plenty of it. If you don’t hydrate enough while increasing fiber, you may experience constipation—one of the very things that fiber can actually aid in fighting. Drink at least eight cups of water a day. (Pro tip: Keep a large water bottle at your side — on your desk, in the car, in the kitchen or wherever you spend most of the day. It will remind you to drink, and you won’t have to stop what you’re doing to refill smaller glasses.)

Choose fiber-rich foods

Now for the fun part: the fiber-rich foods you should be eating. Ideally, you’ll be eating these instead of low-fiber foods (for example, you may swap white bread out for whole grain bread), but when you first start out adding more fiber to your diet, you can at least eat them in addition to what you’re already eating. There are a lot of good sources with more complete lists of fiber-rich foods, but here are some to whet your appetite.

Fruits high in fiber

• Raspberries
• Blackberries
• Pears
• Apples (with the skin)
• Avocado

Vegetables high in fiber

• Green peas
• Broccoli
• Brussel sprouts
• Collard greens

Grains, seeds, and nuts high in fiber

• Whole-wheat spaghetti
• Barley
• Bran flakes
• Quinoa
• Oatmeal
• Whole-grain bread
• Chia seeds

Legumes high in fiber

• Navy beans
• Split peas
• Lentils
• Chickpeas
• Black beans[6]

Plant-based recipes where you can find inspiration for incorporating these foods and others into your routine abound. If you’re hesitant to swap meat or chicken for high-fiber plant-based foods, remember that legumes like beans and lentils and even whole grains are also good sources of protein.

If it’s the convenience of processed foods that feels difficult to give up, try tricks that make fruit and vegetables easier to reach for. Cut, wash and peel food ahead of time and try steaming vegetables for the fastest way to cook. The microwave works, too!

Set a fiber goal

Whatever pace you feel is right for your body, set a goal for yourself each day. It will help you hold yourself accountable. (And if you’re the competitive type, it’ll help to have a challenge to surmount.)

For an easy way to get started, grab an OLIPOP! With 9 grams of fiber per serving, you’ll get 32% of your daily recommended fiber after finishing just one can!

Takeaway

The benefits of eating fiber far outweigh the hurdles to eating more. Choose foods you like, take it slow and you won’t even realize you’re on your way to more fiber and better digestive health. You got this!

Sources

1. “Fiber,” The Nutrition Source, September 18, 2012, https://www.hsph.harvard.edu/nutritionsource/carbohydrates/fiber/.
2. “Gut Bust,” Stanford Medicine, accessed May 17, 2021, https://stanmed.stanford.edu/2016spring/gut-bust.html.
3. Edward C Deehan and Jens Walter, “The Fiber Gap and the Disappearing Gut Microbiome: Implications for Human Nutrition - PubMed,” Trends in Endocrinology and Metabolism: TEM 27, no. 5 (May 1, 2016), https://doi.org/10.1016/j.tem.2016.03.001.
4. “Soluble vs. Insoluble Fiber Information,” Mount Sinai Health System, accessed May 17, 2021, https://www.mountsinai.org/health-library/special-topic/soluble-vs-insoluble-fiber.
5. “Dietary Fiber: Essential for a Healthy Diet,” Mayo Clinic, January 6, 2021, https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983.
6. “Chart of High-Fiber Foods,” Mayo Clinic, January 5, 2021, https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948.

Meet our Expert This article is reviewed by Lauren Manaker MS, RDN, LD. Lauren Manaker is an award-winning registered dietitian, book author, and freelance writer. Her work can be found in many major media outlets and on her women’s health nutrition-focused Instagram account @LaurenLovesNutrition. Raised in sunny South Florida and now living in Charleston, South Carolina, she has a love for the ocean and would be living on a houseboat if she had her way. She currently lives with her husband, young daughter, and 70-pound rescue pup.