The role of fiber in our diets goes beyond keeping our digestion on track. UCLA Health experts say a high-fiber diet supports heart health, regulates blood sugar, promotes weight management and plays a significant role in cancer prevention.
Research shows that fiber can help lower the risk of colorectal cancer by promoting gut health, supporting healthy bacteria and reducing the time harmful substances stay in the digestive tract.
Christina Fasulo, RDN, CNSC, senior dietitian at the UCLA Health GI Nutrition Program, breaks down some benefits of fiber and offers tips on how you can add more to your diet.
Q: Can you explain the role of fiber in maintaining overall health?
Fasulo: Fiber is a vital component of a healthy diet, offering numerous benefits across various aspects of well-being. It supports digestive health by promoting regularity, feeding beneficial gut bacteria, and reducing the risk of conditions like diverticulitis and hemorrhoids.
For heart health, fiber helps lower LDL cholesterol and regulate blood pressure. It also plays a key role in blood sugar control by slowing sugar absorption and improving insulin sensitivity, reducing the risk of type 2 diabetes. In weight management, fiber increases feelings of fullness and stabilizes blood sugar levels to curb cravings.
Additionally, it contributes to cancer prevention by lowering the risk of colorectal cancer and providing antioxidants from fiber-rich foods like fruits, vegetables and whole grains.
Q: How does fiber help reduce the risk of colorectal cancer?
Fasulo: Fiber helps reduce the risk of colorectal cancer — and several other cancers — through multiple mechanisms. It increases stool bulk by absorbing water, allowing waste to pass through the colon more quickly and limiting carcinogen exposure to the colon lining. Additionally, when gut bacteria ferment fiber, they produce short-chain fatty acids (SCFAs) like butyrate, which have anti-cancer properties, including inhibiting cell growth and promoting apoptosis (cell death) in cancerous cells. A fiber-rich diet also supports a healthy gut microbiome, which plays a role in cancer prevention.
Furthermore, fiber aids in weight management by controlling appetite and supporting metabolism, which is crucial since obesity is linked to a higher risk of colorectal cancer.
Q: What are the main differences between soluble and insoluble fiber?
Fasulo: Soluble fiber acts like a “sponge” and dissolves in water and forms a gel in your digestive tract, which slows down food that passes through it. These fibers help support good bacteria in the colon. Soluble fiber also helps manage blood sugar and control cholesterol levels. Soluble fiber is helpful for both constipation and diarrhea.
Insoluble fiber acts like a “street sweeper.” It does not dissolve in water and is less likely to break down, so it passes through your digestive tract more quickly and helps you with constipation.
Q: What are some examples of foods rich in each type of fiber?
Fasulo: Soluble fiber is found in foods like bananas, oats, beans, and the “flesh” of many fruits, while insoluble fiber comes from sources such as wheat bran, fruit and vegetable skins, nuts and seeds.
Q: What are some easy ways to incorporate more fiber into meals and snacks?
Fasulo: Incorporating more fiber into meals and snacks can be simple and delicious. Start your day with whole-grain cereals or oatmeal, and enhance yogurt or smoothies with chia seeds, flaxseeds, or nuts. Adding fruits like berries, bananas, or apples boosts fiber intake, while mixing vegetables into scrambled eggs provides an extra nutrient boost.
For lunch and dinner, swap white rice for whole grains like quinoa or farro, and incorporate beans, lentils, or chickpeas into soups, salads and pasta dishes. A black bean burger or lentil-infused meals, such as soups and shepherd’s pie, are great high-fiber options. Roasted chickpeas make a crunchy snack or salad topping, and adding a side salad or roasted vegetables to meals ensures a fiber-rich diet.
For snacks, opt for nuts, seeds, or air-popped popcorn instead of chips; choose fresh fruit over fruit juice; and pair raw veggies like carrots, cucumbers, or bell peppers with hummus or guacamole for a satisfying, fiber-filled bite.
Q: What are some common fiber myths or misunderstandings?
Fasulo: One misconception is that more fiber is always better, but consuming too much too quickly can cause bloating, gas and digestive discomfort. It’s important to increase fiber intake gradually and stay hydrated.
Another myth is that all fiber is the same, when in reality, fiber varies in solubility (soluble vs. insoluble), viscosity (gel-forming ability) and fermentability (how easily gut bacteria can break it down).
Lastly, many believe that only grains contain fiber, but fiber is also abundant in fruits, vegetables, nuts, seeds and legumes, making it easy to get enough from a well-balanced diet.
Q: For those who experience bloating or discomfort with high-fiber foods, what adjustments can they make?
Fasulo: Gradual adjustments can help improve tolerance. It's best to increase fiber intake slowly, by no more than 2–3 grams every few days, to allow the digestive system to adapt. Staying well-hydrated is also essential, as fiber needs water to move smoothly through the digestive tract — without enough, it can slow digestion and contribute to bloating and gas.
Cooking fiber-rich foods can make them easier to digest by softening the fiber. Additionally, focusing on less fermentable fiber sources may help reduce discomfort, and consulting a dietitian can provide personalized guidance on expanding fiber-rich foods in a way that suits individual tolerance levels.
Q: How does fiber interact with other nutrients or lifestyle factors (e.g., hydration, physical activity) to support colon health?
Fasulo: Exercise stimulates digestion, helping fiber move waste through the colon. Hydration works alongside insoluble fiber to speed up movement through the intestines and promote regularity.
