Fibre and whole grains: what do they really deliver?

This is general information, not medical advice. Always discuss your blood values with your doctor.

1. 1

   More fibre goes with less disease and death

   A series of systematic reviews in The Lancet (Reynolds et al., 2019) pooled 185 prospective studies, nearly 135 million person-years, and 58 clinical trials with 4,635 adults. Compared with the lowest consumers, the highest fibre consumers had 15 to 30% lower all-cause and cardiovascular mortality, and less coronary heart disease, stroke, type 2 diabetes and colorectal cancer. In the trials, people on more fibre had lower body weight, lower systolic blood pressure and lower total cholesterol. The benefit was greatest at 25 to 29 g of fibre a day. The certainty of the evidence was rated moderate.

2. 2

   Whole grains instead of refined grains

   A dose-response meta-analysis of 45 prospective studies (Aune et al., BMJ 2016) found, per 90 g of whole grains a day, meaning three servings of 30 g, about 19% less coronary heart disease, 22% less cardiovascular disease and 17% lower all-cause mortality. Mortality from stroke (14%), cancer (15%), respiratory disease (22%), infections (26%) and diabetes (51%) was also lower. The link was seen for whole grain bread, whole grain breakfast cereals and added bran. For refined grains, white rice or grains in general, there was little evidence of a link. In the Lancet series, the certainty of the evidence for whole grains was low to moderate. These are observational associations, not proof of cause.

3. 3

   Randomised trials: less clear

   A Cochrane review (Kelly et al., 2017) looked for randomised trials of at least 12 weeks. It found nine with 1,414 participants and concluded that there is insufficient evidence of an effect of whole grain diets on cardiovascular outcomes or on risk factors such as blood fats and blood pressure. No study reported heart attacks, strokes or deaths. The review calls for larger and longer trials. In the trials of the Lancet series, whole grains did go with lower body weight.

4. 4

   How much fibre, and where do you stand?

   EFSA (2010) considers 25 g of fibre a day adequate for normal bowel function in adults, and sees extra health benefits at higher intakes. In the 2022-2023 Belgian national food consumption survey, mean intake was 16 g a day (17 g in Flanders), so on average well below that 25 g. Most fibre comes from cereal products, vegetables and fruit. The Lancet authors suggest building meals and snacks around whole grains, vegetables, pulses and fresh fruit.

Updated in October 2026