Most Adults Don’t Get Enough Fiber, Study Finds

Woman and child making dinner

Key Takeaways

  • Only about 7% of U.S. adults meet the recommended intake of fiber, new research suggests.
  • Fiber is important not just for digestive health, but also for lowering cardiovascular risks.
  • When transitioning to more dietary fiber, it’s important to integrate foods gradually to prevent digestive upset.

On average, only 7.4% of U.S. adults meet the recommended daily intake of fiber, according to a study presented at the Nutrition 2021 Live online conference.

Researchers looked at data from more than 14,600 participants of the National Health and Nutrition Examination Survey from 2013 to 2018.

The Institute of Medicine established 14 grams of fiber for every 1,000 calories an “adequate intake,” which means that reaching that goal would involve eating about 25 grams for a 2,000-calorie diet. Women in the study consumed about 9.9 grams per 1,000 calories and men consumed 8.7 grams.

High-fiber foods considered in the research included:

  • Whole grains
  • Vegetables and fruits
  • Nuts
  • Seeds
  • Legumes

Although fiber supplements were not included in the survey, their consumption likely would not have made much of a difference, according to lead researcher Derek Miketinas, PhD, RD, assistant professor of nutrition and food sciences at Texas Woman’s University.

“What tends to provide the most benefits is choosing fiber-rich foods,” he says. “That’s what is strongly associated with significant health benefits.”

More Fiber, Better Health

There are two types of fiber, soluble and insoluble. They work in different ways, but both are considered beneficial for health.

Soluble fiber creates a gel as it dissolves, which helps to slow the absorption of sugar, improving blood glucose regulation. Insoluble fiber doesn’t dissolve in the same way, but does draw water into your stool so it’s easier to route through your digestive system.

Derek Miketinas, PhD, RD

What tends to provide the most benefits is choosing fiber-rich foods, that’s what is strongly associated with significant health benefits.

— Derek Miketinas, PhD, RD

Previous research shows connections between adequate fiber intake of both types and lowering health risks in notable ways, Miketinas adds, such as:

  • Improved diabetes control
  • Lower kidney disease risk
  • Better gastrointestinal function
  • Improved gut health
  • Aids in weight maintenance

One of the most studied associations is between fiber consumption and heart health. For example, research published in JAMA in 1996 found that participants with a high total dietary fiber intake had a 40% lower risk of coronary heart disease.

That’s likely because higher fiber intake reduces the chances of developing metabolic syndrome, according to a 2002 study in The American Journal of Clinical Nutrition. That condition involves a number of factors such as:

  • High blood pressure
  • Excess weight, particularly in the abdominal area
  • High insulin levels
  • Low levels of HDL cholesterol

Gradual Approach

Given the breadth of advantages for increased fiber consumption, it makes sense to add much more to your diet, especially if you’re lacking. However, too much added too quickly can be problematic in the short term, says dietitian Tamara Duker Freuman, RD, who focuses on the dietary management of digestive and metabolic diseases.

“With fiber, even if you’re eating all healthy options, it can be a shock to your system if you ramp up too fast,” she says. That can lead to gas, discomfort, bloating, constipation, abdominal cramping, and diarrhea. Although your body will adjust with enough time, this can be very unpleasant as you get used to increased fiber.

Tamara Duker Freuman, RD

With fiber, even if you’re eating all healthy options, it can be a shock to your system if you ramp up too fast.

— Tamara Duker Freuman, RD

Another key strategy is to drink more water since insoluble fiber attracts water to your digestive system, so you’ll need more hydration to stay in balance.

Freuman adds that it’s important to be aware of all possible sources of fiber. Fruits, vegetables, whole grains, nuts, and seeds are easy to identify, but you may also be getting fiber from products made with nut flour, beverages like smoothies, bean pastas, and plant-based pizza crusts made from cauliflower or other vegetables.

This may be especially true if you’re following a gluten-free diet and eating products that rely on alternative flours.

While it’s helpful to incorporate these into your diet as a way to get more fiber, they can also put you on the fast track to digestive discomfort.

“There’s only so much fiber you can have in one sitting,” says Freuman. “For example, having a quarter cup of chickpeas on your salad is a great choice, but if you’re also having pasta made from chickpea flour, that could be three cups of beans in one meal. That’s a considerable amount if you’re not used to that.”

That said, making the effort to incorporate these foods into your meals and snacks can get you closer to that larger goal of meeting the recommended daily fiber intake.

What This Means For You

Although dietary fiber provides a significant range of health benefits, the majority of people in the U.S. are falling short of getting the recommended amount. Adding more fiber can help, but be sure to take a gradual approach.

4 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Miketinas D, Tucker W, Patterson M, Douglas C. Usual dietary fiber intake in US adults with diabetes: NHANES 2013–2018. Curr Dev Nutr. 2021;5(Supplement_2):1061-1061. doi:10.1093/cdn/nzab053_054

  2. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press; 2006.

  3. Rimm EB, Ascherio A, Giovannucci E, Spiegelman D, Stampfer MJ, Willett WC. Vegetable, fruit, and cereal fiber intake and risk of coronary heart disease among men, JAMA. 1996;275:447-51. doi:10.1001/jama.1996.03530300031036

  4. McKeown NM, Meigs JB, Liu S, Wilson PW, Jacques PF. Whole-grain intake is favorably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring StudyAm J Clin Nutr. 2002;76:390-8. doi:10.1093/ajcn/76.2.390

By Elizabeth Millard
Elizabeth Millard is a freelance journalist specializing in health, wellness, fitness, and nutrition.