Fiber is very important for gut health because it feeds beneficial gut bacteria and promotes healthy bowel movements. However, most Americans meet only about 50% of their daily fiber needs.
“This is largely due to diets high in processed foods and low in fruits, vegetables, whole grains, and legumes,” Lauren Manaker. MS, RDN, LD, Charleston-based registered dietitian, told Health.
Keep reading to learn more about how much fiber you really need for gut health, and how to meet these daily needs.
Fiber supports the gut microbiome. “A fiber-rich diet increases microbial diversity of healthy gut bacteria and increases short-chain fatty acid (SCFA) production, which lowers gut inflammation, strengthens gut lining, and better regulates immune responses,” Sheila Patterson, RD, CDCES, registered dietitian, told Health.
The gut microbiome is also tied to better brain health, chronic disease prevention, and digestion. Fiber promotes digestive regularity throughout the entire gastrointestinal (GI) tract.
“Fiber keeps things moving smoothly, preventing constipation,” explained Manaker. On the other hand, certain types of fiber can add bulk to your stool, which can help prevent diarrhea.
According to the U.S. Dietary Guidelines for Americans, adults should shoot for 14 grams of fiber per 1,000 calories consumed. The Academy of Nutrition and Dietetics also offers a general guideline of at least 25 grams per day for women and 38 grams per day for men.
These numbers are slightly less for kids (anywhere from 14 to 25 grams depending on age and sex) and older adults. “Needs decrease slightly to around 22 grams per day for women over 51 and around 28 grams per day for men of the same age,” Manaker explained.
However, these numbers can fluctuate depending on various circumstances. “Factors such as hydration levels, activity level, metabolic concerns like diabetes, GI issues like irritable bowel syndrome (IBS), pregnancy, and lactation can individualize fiber needs,” shared Patterson.
If you fall into any of these categories, be sure to talk with your doctor to determine your personal fiber goals.
There are two main types of fiber—soluble and insoluble—and each works differently in the gut.
Soluble Fiber
“Soluble fiber dissolves in water to form a gel-like substance. It slows digestion, helps regulate blood sugar levels, and lowers cholesterol,” said Manaker. This is the type of fiber that helps quell diarrhea and serves as a prebiotic (or food for healthy bacteria) in the gut microbiome.
Rich sources of soluble fiber include:
Insoluble Fiber
“Meanwhile, insoluble fiber helps with insulin sensitivity along with digestion by adding bulk and moving stool, reducing constipation,” added Patterson.
Foods high in insoluble fiber include:
- Wheat bran
- Berries
- Cantaloupe
- Brown rice
- Quinoa
- Leafy greens like spinach, kale, broccoli, and cauliflower
- Nuts and seeds
Thankfully, most foods with fiber have a mix of both soluble and insoluble fiber. You’ll only find fiber in plant-based foods like fruits, veggies, whole grains, nuts, seeds, and legumes.
One of the most popular ways to boost fiber intake is with hearty, nutrient-dense breads. However, not all breads are created equally when it comes to fiber content and health benefits.
Here are some tips for shopping for a fiber-rich, healthy bread:
- Check the fiber content: Aim for a bread that contains at least 3 grams of fiber per slice—the more, the better.
- Look for ‘whole’ on the ingredient list: “When shopping for bread, look for whole wheat or whole grain as the first ingredient. Avoid options with refined or enriched flours,” said Patterson.
- Be wary of added sugars: Though they won’t impact the fiber content, breads with high amounts of added sugars or other artificial ingredients can detract from the loaf’s overall gut health benefits. Look for less than 5 grams of added sugar per slice.
- Go for nutrient-dense add-Ins: If you see whole grain bread with added nuts or seeds, it usually means extra fiber and micronutrients—making it a healthier choice.
- Watch for the whole grain stamp: “The Certified Whole Grain stamp means the product contains at least half a serving of whole grains per portion. It’s a reliable way to ensure you’re getting real whole grains, not just ‘wheat-colored’ bread,” Manaker explained.
“If someone has very low fiber intake and wants to increase it, they should start in smaller increments, increasing gradually by about 2 to 3 grams of fiber per day until they hit their goal,” shared Patterson. This can help avoid the unwanted GI symptoms—like gas, bloating, and constipation—that are often associated with doing too much too soon.
Fiber also needs plenty of fluid to move through the GI tract, so aiming for at least 8 cups of water or some other unsweetened, decaffeinated beverage per day is ideal. This further helps prevent GI complaints, particularly constipation, when increasing your numbers.
If you’re ready to get started, here’s what a sample day of high-fiber eating could look like:
- Breakfast: Greek yogurt bowl with berries, whole grain granola, and chia seeds
- Lunch: Turkey sandwich on whole grain bread piled with veggies like tomato, cucumber, lettuce, sprouts, and pickles
- Dinner: Quinoa and brown rice grain bowl with roasted tofu, pickled red onions, a variety of raw veggies, and a homemade vinaigrette
- Snacks: Cut veggies and hummus; whole grain crackers with nut butter; dried or fresh fruit
Fiber is a complex carbohydrate that supports a healthy gut through boosting the vitality of your gut microbiome and increasing digestive regularity.
Different types of fiber do slightly different things, but most fiber-rich foods give you a mix of both soluble and insoluble fiber, helping you get the full range of benefits. Plant-based foods like whole grains, nuts, seeds, fruits, veggies, and legumes are the best places to look for fiber.
