What Are the Health Benefits of Fiber (and How Much Should You Have)?

People born in the 1990s are twice as likely to develop colorectal cancer compared to those born in the 1950s and, by 2030, colorectal cancer is estimated to become the leading cause of cancer-related death in people under 50. These are scary stats, and so it’s no wonder that fiber (and its health benefits!) has gone viral.

Research shows that fiber intake is associated with reduced risk of cardiovascular disease and certain cancers (including colorectal). It's one of the most evidence-backed dietary staples. But despite all the buzz, most of us aren't actually eating enough of it. Let's break down what fiber really is, why it matters for your health (including your fertility), and how to get more of it without overthinking it. 

Think of fiber as the structural scaffolding of plants: it's the part of fruits, vegetables, grains, and legumes that your body can't fully digest. Fiber is a carbohydrate that resists digestion and absorption in the small intestine but provides health benefits to the body. Unlike other carbs that get broken down into sugar for energy, fiber travels through your digestive system relatively intact, doing important work along the way (more on that shortly). 

There are two main types of fiber, and they each have different benefits: 

You don't need to worry about which type you're eating; most plant foods contain both, and your body benefits from having a variety of both. 

The research on fiber is pretty compelling. Large-scale studies examining hundreds of studies found that higher fiber intake is associated with reduced cardiovascular disease mortality and all-cause mortality. For every 15-gram increase in whole grains eaten per day, deaths and incidence of coronary heart disease, type 2 diabetes, and colorectal cancer decreased by 2 to 19%. 

Fiber is definitely good for gut health, as it contains prebiotics. Prebiotics escape digestion in the upper gastrointestinal tract and are fermented by bacteria in the colon, which supports the structure and diversity of the gut microbiome. This fermentation process produces short-chain fatty acids (SCFAs), which are compounds that have anti-inflammatory effects and support the health of your gut lining. 

High-fiber diets have consistently been shown to increase microbiome diversity and SCFA-producing bacteria in the gut. More diversity in your gut microbiome is linked to better health outcomes, from improved immune function to better metabolic health.

Fiber keeps your digestive system running smoothly in several ways: 

• Insoluble fiber adds bulk to your stool and speeds up transit time through your intestines, which helps prevent constipation. 
• Soluble fiber feeds your beneficial gut bacteria and can help firm up loose stools when needed

Together, these actions promote regular, comfortable bowel movements and support overall digestive health.

The relationship between fiber and weight is nuanced. Most individual fiber types don't show significant effects on appetite or energy intake in acute studies, but there are studies that show weight loss with high-fiber diets. The mechanisms behind fiber's weight management benefits likely involve feeling fuller for longer, displacing higher-calorie foods, and the benefits of gut bacteria fermentation.

• Increase satiation (how full you feel)

• Reduce appetite

• Lower body weight

• Decrease BMI and waist circumference

• Decrease insulin-resistance

Not getting enough fiber can have larger consequences than just constipation. A 2020 study confirmed that low fiber intake is linked to many modern chronic diseases, including colorectal cancer, breast cancer, cardiovascular disease, and obesity.

The good news is these risks are modifiable, and increasing your fiber intake through whole plant foods can help reverse many of these negative health outcomes. The same study found that even a 10% increase in fiber could reduce colorectal cancer risk by 10%.

The best sources of fiber are whole, minimally processed plant foods. Having a variety of different types of plant foods throughout the day will help add up to your daily goal. 

Beans and legumes have a lot of fiber: just a half cup of cooked black beans delivers about 7.5 grams of fiber. Whole grains like oats and quinoa are good sources, too. 

Fruits like raspberries, pears, apples (with the skin) will add 3 to 5 grams to your daily goal, and avocados are an underrated high-fiber source. With vegetables, the cruciferous veggies are the best sources: broccoli, cabbage, brussels sprouts, and cauliflower. 

Another favorite source: chia and flax seeds—just one tablespoon of chia seeds has 4 to 5 grams of fiber.

While fiber supplements can help you reach your daily goals, getting fiber from whole foods is ideal. Whole foods provide not just fiber but also vitamins, minerals, and antioxidants—all good for overall health. 

That said, if you're struggling to meet your fiber needs through diet alone, supplements like psyllium husk can be helpful—just check with your healthcare provider first, as fiber supplements could potentially interact with medications.

Start your day with a high-fiber breakfast, like oatmeal topped with raspberries and chia seeds. Add beans or lentils to soups, salads, and grain bowls. Keep the skin on fruits and vegetables when possible (think apples, potatoes, and cucumbers). Snack on fresh fruit, raw veggies with hummus, or a handful of nuts instead of processed snacks.

Make sure to increase your fiber intake gradually and to drink a lot of water; adding too much too fast can cause bloating, gas, and discomfort. 

Both the USDA and Canadian government guidelines recommend 25 grams of fiber daily for women and 38 grams for men under age 50, with slightly lower recommendations (21 and 30 grams, respectively) for those over 50. The average North American consumes only 10 to 16 grams of fiber per day, and only about 5% of the population meets the recommended intake.

If you're not sure where you fall, a simple rule of thumb is to aim for 14 grams of fiber for every 1,000 calories you consume. Breaking this down into meals can make it feel more manageable—try for 10 to 15 grams of fiber at each meal rather than focusing on the daily total.

The connection between fiber and fertility isn't as widely discussed as other fertility factors, but the research suggests it matters—especially when it comes to hormonal balance and metabolic health. 

Fiber affects female fertility in a few ways. Research shows that fiber can decrease estrogen reabsorption in the colon and increase fecal excretion. This helps the body maintain balanced estrogen levels, which is important for regular ovulation and menstrual cycles. When estrogen is properly regulated, other reproductive hormones can respond appropriately to support fertility. One large study found that each increase in dietary fiber consumption was associated with a 32% lower risk of infertility. 

Fiber also has a role in maintaining a healthy weight and improving insulin sensitivity—particularly relevant for conditions like PCOS, where insulin resistance can mess with ovulation, making it more difficult to get pregnant. 

Fiber also supports a healthy gut microbiome, which plays a role in metabolizing and regulating estrogen levels.Fiber feeds beneficial gut bacteria, which convert bound estrogens into their free and active forms—meaning a healthy, diverse microbiome supports proper estrogen metabolism and hormonal balance, both of which are essential for fertility.

But, very high fiber intakes were also associated with lower reproductive hormone concentrations and increased risk of anovulation (that’s no ovulation) in one study of premenopausal females. The takeaway? A balanced amount of fiber is beneficial, but you can go overboard, especially if you’re trying to conceive. Aim for the recommended daily intake, or chat with your doctor.

While research specifically on fiber and male fertility is limited, the broader metabolic benefits of fiber intake are also relevant for men. 

Fiber's role in maintaining healthy weight, supporting insulin sensitivity, and reducing inflammation can all positively impact male reproductive health. A systematic review on male sperm quality showed that healthy dietary patterns had beneficial effects on sperm concentration, total sperm count, and progressive sperm motility in males, all which affect male fertility. And, a healthy gut microbiome supported by adequate fiber intake contributes to overall hormonal balance and metabolic function, which are important for fertility in both sexes.

Are you convinced yet? Fiber is one of those nutrients that deserves all the attention it's getting. From supporting your heart and gut health to potentially enhancing fertility, there are plenty of reasons to make sure you're getting enough. 

Start where you are, add fiber-rich foods gradually, drink plenty of water, and pay attention to how your body responds. Your digestive system (and the rest of your body) will thank you.