• Fiber is a key nutrient for preventing colon cancer and supporting a healthy gut microbiome.
• Adding a few high-fiber foods to your daily rotation can help you hit the recommended dose.
• A doctor specializing in cancer prevention said her top high-fiber hacks include snacks and smoothies.

As colorectal cancer is on the rise among people in their 20s, 30s, and 40s, a common nutrient can help reduce your risk — and you're probably not getting enough of it.

Fiber is a key nutrient for gut health, but more than 90% of Americans don't get the recommended 25 to 34 grams of fiber daily.

And it could be a major tool in the fight against colorectal cancer, now the leading cause of cancer deaths in Americans under 50.

"Increasing fiber is really, really important for prevention of bowel cancer," said Dr. Bea Bakshi, a primary care physician and CEO of cancer detection company C the Signs.

While there's no sure-fire way to prevent the disease, small diet changes can make a big difference for boosting fiber intake and long-term health, Bakshi told Business Insider.

Here's where to start.

Mix in nuts and seeds

One of the easiest ways to start eating more fiber is to build on what you typically eat, according to Bakshi.

"Many people think increasing fiber requires completely changing their diet, but in reality, small additions to meals you already enjoy can quickly increase your intake," she said.

Nutrient-dense seeds like chia and flax are rich in fiber and other nutrients. Try sprinkling them into yogurt or oatmeal, Bakshi suggests.

Nuts like almonds, walnuts, and cashews are another accessible source of fiber and healthy fats, making them a great snack or salad topping.

Stock up on beans

For the best budget-friendly superfood, look no further than legumes. Lentils, black beans, and chickpeas are versatile cooking staples that each pack 12 to 15 grams of fiber per cup.

Beans are packed with protein, too. Adding them to a hearty soup, stew, or salad makes for a healthy lunch to help you cut back on ultra-processed foods linked to cancer risk, like deli meat and hot dogs.

"Processed meat is really the big one because of the impact it has on the gut microbiome," Bakshi said.

Switch to whole grains

To boost your fiber intake without overhauling your diet, replace refined grains like white bread, pasta, and cereals with whole-grain alternatives.

Bakshi recommends whole-grain hacks like:

• Starting your day with a bowl of oatmeal.
• Snacking on popcorn — yes, it counts as a whole grain! — ideally with herbs and spices for flavor instead of butter and salt.
• Use whole-grain bread for toast and sandwiches.

Snack on berries and apples

Fruit can be an excellent source of fiber, but some fruits are more nutritious than others, Bakshi said.

Raspberries and blackberries are among the highest-fiber fruits at about 8 grams per cup, and make a convenient snack or topping for oatmeal, yogurt, or salads.

Fruits like apples and pears are also high in fiber if you eat the skin. Berries and apples contain micronutrients called flavanols that help protect against inflammation and disease, too.

Make a superfood smoothie

If you want to get nearly all your daily fiber in one simple recipe, Bakshi said her go-to strategy is a smoothie.

"If I don't have time, I can just shove everything in a blender, and I feel less guilty," she said.

Her recipe has a creamy texture and healthy fats thanks to avocado, and it packs around 30 grams of fiber.

Dr. Bakshi's fiber-rich smoothie recipe:

In a blender, mix:

• 1 cup raspberries
• 2 whole kiwis (with skin)
• 1 medium banana
• 1 tablespoon chia seeds
• 1 tablespoon ground flaxseed
• ½ avocado
• 1 cup unsweetened almond or oat milk (adjusting to your personal preference).

Unlike juice, which removes much of the fiber from fruits and veggies, smoothies retain nutrients, making it easier to eat high-fiber foods even on the busiest schedule.