Eating the right carbs can help lower your mortality risk.

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Whole wheat bread can help up your fiber intake to the recommended level. Getty Images

For decades, doctors, dietitians, and others have been encouraging people to get enough fiber in their diets.

A growing body of evidence suggests that fiber plays an important role in promoting good health and preventing chronic illness.

According to a of systematic reviews and meta-analyses published this month in The Lancet, people with the highest-fiber diets have 15 to 30 percent lower all-cause and cardiovascular-related mortality than people with the lowest-fiber diets.

People who eat more fiber are also less likely to develop coronary heart disease, type 2 diabetes, or colorectal cancer, according to researchers.

Higher fiber intake was also linked to lower body weight and cholesterol.

“The study does not surprise us as science has reported health benefits of fiber for some time,” Kristi L. King, MPH, RDN, CNSC, LD, a dietitian at Texas Children’s Hospital and national spokesperson for the Academy of Nutrition & Dietetics, told Healthline.

“But it does emphasize the magnitude of benefits a high-fiber diet provides,” she added.

The new study was commissioned by the World Health Organization (WHO) to guide the development of recommendations for daily fiber intake.

The authors reviewed and synthesized data from multiple observational studies and clinical trials, bringing together nearly 40 years of research.

They included 185 observational studies and 58 clinical trials in their analysis.

For every 8 grams of increased fiber intake per day, they found that total deaths and incidence of coronary heart disease, type 2 diabetes, and colorectal cancer dropped by 5 to 27 percent.

For every 15 grams of increased whole grain intake per day, total deaths and incidence of coronary heart disease, type 2 diabetes, and colorectal cancer declined by 2 to 19 percent.

The results of this study suggest that eating 25 to 29 grams of fiber per day is enough to provide protective benefits. But eating more fiber may provide even greater protection.

Fiber is found in the skins, stalks, seeds, and flesh of plants.

Some diet plans and eating patterns include more fiber than others.

For example, the average American diet is low in fruits, vegetables, whole grains, and other fiber-rich foods. Many Americans eat a lot of refined grain products, which are lower in fiber than whole grain alternatives.

The “keto diet,” “paleo diet” and other low-carbohydrate diets also include little to no whole grains. Low-carb diets often restrict other fiber-rich foods, too, such as fruits, vegetables, and legumes.

In contrast, the Mediterranean diet is rich in plant-based foods, including fruits, vegetables, legumes, nuts, seeds, and whole grains. These foods are excellent sources of fiber.

If someone is following a very low-carb diet, it might be hard to get enough fiber from food alone.

To increase their fiber intake, low-carb dieters can choose plant-based foods that are relatively low in carbohydrates but high in fiber.

Some examples include broccoli, cauliflower, cabbage, and other leafy greens. Nuts and seeds are also low in carbs but rich in fiber.

In certain cases, a doctor or dietitian might encourage those on a low-carb diet to take fiber supplements.

“Historically, when people start on a very low-carbohydrate diet, fiber supplementation is generally recommended,” Judith Wylie-Rosett, EdD a professor in the Department of Epidemiology and Population Health at the Albert Einstein College of Medicine, told Healthline.

However, she added, more research is needed to learn how fiber supplements affect the digestive system and other parts of the body.

To date, most of the research on dietary fiber has focused on naturally fiber-rich foods rather than processed supplements.

It’s possible that fiber supplements don’t provide the same benefits as fiber-rich whole foods.

“We’re in an era where we’re exploring the microbiome,” Wylie-Rosett said, “and I’m not sure if a processed food item that’s low in net carbohydrates but high in fiber is the same as eating seeds, or broccoli, or whatever.”

If your diet is low in fiber, King recommends increasing your fiber intake gradually rather than all at once.

This might help you minimize the uncomfortable symptoms that can arise when you eat too much fiber, such as abdominal pain, bloating, gas, constipation, or diarrhea.

“Allow your body to adapt,” King suggested. “Try adding a piece of fruit to breakfast. Next add an additional vegetable to lunch and dinner.”

“Also be sure to drink plenty of fluids,” she added. “Fiber and fluids are friends. You need the fluids to help keep the fiber moving through the body.”

Examples of high-fiber foods include:

  • split peas (16 grams of fiber per cooked cup)
  • black beans (15 grams of fiber per cooked cup)
  • chia seeds (10 grams of fiber per ounce)
  • green peas (9 grams of fiber per cooked cup)
  • raspberries (8 grams of fiber per raw cup)
  • whole-wheat pasta (6 grams of fiber per cooked cup)
  • instant oatmeal (5 grams of fiber per cooked cup)
  • brown rice (3.5 grams of fiber per cooked cup)

Other legumes, seeds, nuts, vegetables, fruits, and whole grains provide good sources of fiber, too.