95% of Americans do *not* eat the recommended amount of dietary fiber.
This is due to low intakes of fiber-rich foods like fruits, vegetables, and legumes and seeds, and the fact that ultra-processed foods (UPF) are stripped of fiber.
Let’s talk numbers.
The recommended daily fiber intake is 20 to 35 g/day in most countries.
Many countries have adopted energy-adjusted levels of dietary fiber as the recommended amounts: for example, the Institute of Medicine recommends 14g of fiber per 1000kcals consumed. So the daily value is 28g with a 2000kcal diet.
Recommendations are also different by gender and age with 38g/day for males and 25 g/day for females age 19-50 years old, and lower values for older individuals.
However, recent studies show that higher intakes of dietary fiber, over 40 g/day, could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer.
Dietary fiber has been a cornerstone of human nutrition for more than a million years. Estimates suggest that early hunter-gatherers relied heavily on fruits and wild grains, and later agricultural societies regularly consumed around 100 grams of fiber each day.
Americans current average fiber intake is a meager 15 g/day, below any of the recommended amounts.
How to increase your dietary fiber intake?
Unless supplements are recommended by your healthcare professional, the best way to increase fiber is to eat a fiber-rich diet. Fiber supplements don't provide the variety of fiber, vitamins, minerals, and other healthful nutrients that whole foods do.
Your best food choices are berries, nuts and legumes. Salads and many vegetables are healthy choices but not fiber-dense.
It is important to increase fiber intake gradually to avoid excessive gas. Professor Whiteson, University of California Irvine (UCI) and Director of the UCI Microbiome Center advises that “Your gut is like a muscle. You have to start slowly.”
When not to eat a high-fiber diet
In some circumstances, it is recommended to eat less fiber. This may ease symptoms of a condition or help the digestive tract heal from a treatment. For example, one should not eat fiber before a colonoscopy or after digestive surgeries. It is important to follow healthcare professionals’ advice for one’s specific situation.
Sources
Dietary Fiber Intake and Gut Microbiota in Human Health. Microorganisms.(2022). https://www.mdpi.com/2076-2607/10/12/2507
Dietary guidelines for Americans 2020-2025.(2020). https://www.dietaryguidelines.gov/
https://www.ucihealth.org/blog/2024/06/studying-the-gut-microbiome
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