DEAR MAYO CLINIC: Fiber has been getting a lot of attention in the news lately. What exactly is dietary fiber, and why is it important to my overall health?
ANSWER: Dietary fiber refers to the parts of plant-based foods that your body can’t digest or break down. Unlike proteins, fats or simple carbohydrates, fiber passes through the digestive system largely intact. Because your body can't digest it, fiber becomes an important fuel source for the trillions of microbes that live in your gut.
As food moves through the digestive tract, nutrients your body can absorb are taken up earlier in the process. What remains — much of which is fiber — travels to the colon, where gut bacteria use it for energy.
Dietary fiber is often associated with digestion, but its role in the body goes far beyond keeping you regular. Fiber plays an important part in gut, heart, immune and metabolic health. Research shows that adequate fiber intake helps:
- Lower cholesterol levels and reduce blood pressure.
- Improve blood sugar control, aiding in the prevention and management of type 2 diabetes.
- Decrease the risk of colorectal cancer, stroke and chronic inflammation.
- Manage a healthy weight.
- Regulate immune responses.
- Maintain a healthy and diverse gut microbiome, which supports many aspects of overall health.
Fiber is often described as soluble or insoluble, based on whether it dissolves in water or not. However, this distinction is less important for overall health than how fiber functions in the body. A more meaningful way to think about fiber is whether it’s fermentable or nonfermentable. Here’s what this means:
- Fermentable fiber can be broken down by gut microbes and used as fuel. This process produces beneficial compounds, such as short-chain fatty acids.
- Nonfermentable fiber isn’t readily used by microbes and mainly adds bulk to your stool, which helps support regular bowel movements.
While you may hear about the benefits of taking supplements to add fiber to your diet, but fiber is best obtained from food rather than supplements. That’s because many whole foods contain a mix of different fibers, which is especially beneficial for gut health. Fiber-rich foods include:
- Fruits, such as berries, pears and apples.
- Vegetables, like broccoli, Brussels sprouts and leafy greens.
- Legumes, including lentils, chickpeas and beans.
- Nuts and seeds, such as almonds, chia seeds and flax seeds.
- Whole grains, including whole-wheat bread, oats and wheat bran.
It's important to eat a variety of these foods. The more different types of fiber-rich foods you eat, the more different types of fiber you'll get, which is optimal for your health. Making small, sustainable changes, such as choosing whole-grain bread instead of white bread or swapping chips for nuts or fruit, can add up over time.
Most adults who are in good health should aim for 30 to 40 grams of fiber per day. However, your fiber needs can vary by age and general health. For example, older adults may need to balance fiber intake with adequate calories and protein.
As you increase your fiber intake, you may experience some abdominal discomfort, bloating and gas. To prevent or lessen these symptoms, gradually add more fiber to your diet rather than increasing your intake all at once. A helpful approach is to:
- Increase fiber intake by about 3 grams per week. This can be as easy as adding just 1/2 cup peas, squash or cauliflower; 1 cup carrots; 1 medium sweet potato; 1 cup brown rice; 3 tablespoons of shredded coconut; or 2 tablespoons of sesame seeds.
- Maintain that level for seven to 10 days before increasing again.
- Drink plenty of water, aiming for 80 ounces a day.
Slowly increasing your fiber intake allows your digestive system and gut microbes time to adapt, and any symptoms will improve after a short while.
Fiber is an essential part of a healthy diet. By eating a variety of plant-based foods, increasing fiber intake gradually and staying well hydrated, you can support gut health and overall well-being while making fiber goals more achievable and sustainable.
Purna Kashyap, M.B.B.S., Gastroenterology, Mayo Clinic, Rochester, Minnesota