Fiber is one of the nutrients people often know they need but rarely know how much to aim for. The established dietary reference target is about 14 grams of fiber per 1,000 calories, while NIDDK guidance gives a practical adult range of 22 to 34 grams per day, depending on age and sex.
A useful daily target
For many adults, 25 to 30 grams a day is a practical target. Someone eating 2,000 calories would reach the 14 grams per 1,000 calories benchmark at about 28 grams of fiber.
The exact number is not a pass or fail test. Energy needs, age, sex and overall diet all affect the appropriate intake.
Where the fiber should come from
The best approach is to build fiber into ordinary meals rather than relying heavily on supplements. High-fiber foods include beans and lentils, whole grains, vegetables, fruits, nuts and seeds.
For example, oats with fruit at breakfast, beans or lentils with lunch, vegetables with dinner and a handful of nuts or seeds can add up quickly.
The 2025 to 2030 Dietary Guidelines emphasize whole, nutrient-dense foods, including vegetables, fruits and whole grains. Fiber naturally comes along with many of these foods.
What research says about health
Fiber has a well-established role in digestive health. NIDDK notes that adequate fiber can help prevent and treat constipation, especially when people also drink enough fluids.
Research also points to broader associations. A major systematic review and meta-analysis published in The Lancet found that higher fiber intake was associated with lower risks of coronary heart disease, stroke, type 2 diabetes and colorectal cancer. The authors reported the strongest evidence for benefit at roughly 25 to 29 grams per day, with potential additional benefit at higher intakes.
That does not mean fiber alone prevents these diseases. Diet quality and other lifestyle factors matter, and much of the long-term evidence comes from observational research.
How to increase fiber without discomfort
If your current intake is low, increase it gradually. A sudden jump can cause gas, bloating or abdominal discomfort. Drinking enough fluid can also help fiber work effectively.
A simple goal is to add one high-fiber food at a time: swap refined grains for whole grains, add beans to a meal, eat fruit instead of juice, or add vegetables and seeds to familiar dishes.
The bottom line
For most adults, aiming for roughly 25 to 30 grams of fiber a day is a useful starting point, while the broader reference target is about 14 grams per 1,000 calories. Focus on varied whole foods and increase intake gradually.
Sources: Dietary Guidelines; NIDDK; National Academies dietary reference intake framework; Reynolds et al., The Lancet, 2019.
