Fiber: how much you need per day and where to get it
Nutrition
Key points
- Aim for at least 25 to 29 g a day; the Dietary Guidelines suggest 14 g per 1,000 calories.
- High fiber intake is linked to a 15% to 30% lower risk of several chronic diseases.
- Increase gradually and drink enough water to avoid bloating.
- Get fiber from food rather than supplements whenever possible.
What fiber is
Dietary fiber is the part of plant foods that our bodies cannot digest on their own. It adds bulk, keeps you full longer, slows the absorption of sugar and feeds beneficial gut bacteria.
Fiber is found only in plant foods. Meat, fish, eggs and dairy contain none. The Dietary Guidelines for Americans call fiber a “nutrient of public health concern” because more than 90% of women and 97% of men fall short.
How much you need
The most complete analysis is a series of systematic reviews and meta-analyses commissioned by the WHO and published in The Lancet. Researchers pooled data from 185 prospective studies and 58 clinical trials. People with the highest fiber intake had a 15% to 30% lower risk of death from all causes and from cardiovascular disease, and lower rates of coronary heart disease, stroke, type 2 diabetes and colorectal cancer (Reynolds et al., 2019).
The greatest benefit was seen at 25 to 29 g a day, and the authors noted that higher intakes probably offer even more protection. The Global Burden of Disease study also identified a lack of whole grains as one of the leading dietary risks worldwide (Afshin et al., 2019).
Where to find it
Approximate fiber per typical serving:
| Food | Serving | Fiber (approx.) |
|---|---|---|
| Lentils, cooked | 1 cup | 15 g |
| Black beans, cooked | 1 cup | 15 g |
| Raspberries | 1 cup | 8 g |
| Pear with skin | 1 medium | 5–6 g |
| Broccoli, cooked | 1 cup | 5 g |
| Oatmeal, cooked | 1 cup | 4 g |
| Apple with skin | 1 medium | 4 g |
| Almonds | 1 oz (about 23) | 3.5 g |
| Ground flaxseed | 1 tablespoon | 2–3 g |
Beans and lentils are the clear champions: one bowl of lentil soup can cover half your daily need.
How to add more fiber in a week
- Breakfast: oatmeal with berries and a spoonful of ground flaxseed.
- Lunch: a soup, chili or salad with beans or lentils.
- Snack: an apple, a pear or a handful of nuts instead of cookies.
- Dinner: half a plate of vegetables and a whole-grain side.
- Bread: choose loaves where whole-wheat flour is the first ingredient and check the Nutrition Facts label for at least 3 g of fiber per slice.
Fruit and vegetables add substantial fiber, and eating enough of them is linked to lower disease risk on its own (Aune et al., 2017).
Go slowly and drink water
If you eat little fiber now, do not double it overnight. Add 3 to 5 g a week and drink enough water. Your gut will adapt gradually and discomfort such as bloating will be minimal.
Frequently asked questions
How much fiber do I need a day?
Meta-analyses in The Lancet found the greatest benefit at 25 to 29 g a day or more. For comparison, one cup of cooked lentils has about 15 g of fiber.
Can fiber supplements replace food?
Supplements such as psyllium can help with specific conditions on a doctor’s advice, but whole foods also provide vitamins, minerals and other beneficial compounds, and most of the research is about food.
Why do beans cause gas?
Gut bacteria ferment some of the carbohydrates in beans. If you increase portions gradually and rinse canned beans or soak and cook dried beans well, your gut usually adapts.
Sources
- Reynolds et al. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet 393(10170):434-445. doi:10.1016/S0140-6736(18)31809-9
- Afshin et al. (2019). Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The Lancet 393(10184):1958-1972. doi:10.1016/S0140-6736(19)30041-8
- Aune et al. (2017). Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology 46(3):1029-1056. doi:10.1093/ije/dyw319
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