How much fibre do you need a day? What a major Lancet review found

Protein gets most of the attention in nutrition, but fibre may be the nutrient most people are missing. A major review commissioned by the World Health Organization and published in The Lancet shows how much it matters and gives a clear daily target.

What is fibre?

Dietary fibre is the part of plant foods that your body cannot digest in the small intestine. Instead, it passes on to the large intestine, where some types are fermented by gut bacteria. It is found in vegetables, fruit, legumes, whole grains, nuts and seeds. Animal foods such as meat, eggs and dairy contain essentially none.

What the Lancet review found

The researchers analysed 185 prospective studies (almost 135 million person-years of data) and 58 clinical trials with 4,635 adults ^[1]. Comparing people who ate the most fibre with those who ate the least, they found ^[1]:

• a 15 to 30% lower risk of death from any cause and from cardiovascular disease;
• a lower incidence of coronary heart disease, stroke, type 2 diabetes and colorectal cancer.

In the clinical trials, higher fibre intakes led to lower body weight, systolic blood pressure and total cholesterol compared with lower intakes ^[1].

How much do you need?

The reduction in risk was greatest at 25 to 29 g of fibre a day ^[1]. The dose-response curves also suggested that higher intakes could bring even more protection against cardiovascular disease, type 2 diabetes, and colorectal and breast cancer ^[1].

This fits the European Food Safety Authority's reference value: EFSA considers 25 g of fibre a day adequate for normal bowel function in adults, and notes that higher intakes are linked to a lower risk of heart disease and type 2 diabetes and to better weight maintenance ^[2].

How certain is this?

The authors rated the certainty of the evidence for fibre as moderate ^[1]. Most of the data on disease and mortality comes from observational studies: people who eat more fibre often have other healthy habits too, so these results show an association rather than proof of cause. The clinical trials, which do test cause and effect, looked at risk factors such as weight, blood pressure and cholesterol rather than at disease itself ^[1].

How to eat more fibre

• Add legumes. Lentils, chickpeas and beans in soups, salads or as a side dish are among the richest sources.
• Choose whole grains. Oats, wholegrain bread, brown rice or buckwheat instead of refined versions.
• Vegetables at every main meal. Aim for half the plate.
• Eat fruit whole. Whole fruit keeps its fibre, while juice loses most of it.
• Nuts and seeds as snacks. A handful of nuts, or chia or flax seeds in yoghurt or oats.

Increase it gradually

A sudden jump in fibre can cause bloating and gas. Increase it over a few weeks and drink enough water. If you have a digestive condition such as irritable bowel syndrome or inflammatory bowel disease, or a doctor has told you to follow a low-fibre diet, talk to your doctor or a dietitian before changing your fibre intake.

The personalised meal plan builds enough fibre into meals you actually enjoy, without counting grams.