Dietary Fibre: Soluble and Insoluble Types, ICMR-NIN Intake and Indian Sources

Dietary fibre is the part of plant food that your small intestine cannot digest, so it travels on to the large intestine, where it adds bulk and is partly fermented by gut bacteria. ICMR-NIN's Nutrient Requirements for Indians, 2020, treats about 15 g for every 1,000 kcal eaten as a safe intake, which works out to 30 g a day for a sedentary man and 25 g for a sedentary woman. Whole pulses, millets, whole-wheat atta, vegetables and fruit eaten whole supply it. This entry sits in the carbohydrates section of the handbook.

What is dietary fibre?

It is the group of plant carbohydrates that human digestive enzymes cannot break down. ICMR-NIN's Dietary Guidelines for Indians, 2024, describes fibre as the indigestible part of vegetables, fruits, whole grains, pulses, nuts and seeds: cellulose in vegetables and whole grains, gums and pectin in vegetables, fruits and cereals. Because it is not absorbed, fibre works inside the gut. The same document credits it with slowing the absorption of carbohydrate and fat, adding to the feeling of fullness after a meal and increasing the bulk of the stool.

Fibre is a carbohydrate, but it behaves differently from starch and sugar: ICMR-NIN lists starch and fibre as the two forms of complex carbohydrate, and only the first is digested. The Indian Food Composition Tables 2017 measure total dietary fibre by an enzymatic gravimetric method, and report the soluble and insoluble fractions separately for each food.

Soluble and insoluble fibre compared

Soluble fibre dissolves in water and forms a gel. Pectin, gums and the beta-glucan of oats belong here. Insoluble fibre, mainly cellulose, does not dissolve and gives the stool its bulk. No Indian or WHO guideline sets a separate target for each kind, and almost every plant food carries both. In IFCT 2017, whole-wheat atta has 11.36 g of fibre per 100 g, of which 1.63 g is soluble, while barley has 15.64 g with 5.66 g soluble.

How much fibre do you need in India?

ICMR-NIN's 2020 report sets an adequate intake of 30 g a day for a sedentary man and 25 g for a sedentary woman, rising with activity to 50 g and 40 g for heavy work. The figures follow from one rule: about 15 g of fibre for every 1,000 kcal, or 30 g for 2,000 kcal. This was the first time the expert group set fibre against energy intake. The report labels the values adequate intakes and gives no estimated average requirement for fibre.

The WHO's 2023 carbohydrate guideline is set differently. It recommends that adults eat at least 25 g of naturally occurring dietary fibre a day, with at least 15 g for children aged 2 to 5, 21 g at 6 to 9 and 25 g from the age of 10. The Indian figure is higher for most adults because it scales with energy. The article on how much fibre you need in a day compares other national targets. To see what the Indian rule means for you, estimate your energy need with the calorie calculator and allow 15 g per 1,000 kcal.

Which Indian foods have the most fibre?

Whole pulses lead, followed by millets and whole-wheat atta, with fruit and vegetables adding smaller amounts per 100 g. Averaged across each food group, ICMR-NIN's 2024 guidelines give 12 g of fibre per 100 g raw for pulses, 9 g for nuts, 7 g for millets, 6 g for cereals and 2 g each for vegetables, green leafy vegetables and fruits. IFCT 2017 gives whole Bengal gram 25.22 g per 100 g against 15.15 g for chana dal, and raw milled rice only 2.81 g against 11.36 g for atta.

The pulse and cereal portions above are the raw amounts in the dinner and lunch of ICMR-NIN's sample menu for a sedentary man: 25 to 30 g of pulses, the dal for one person's katori, and 80 g of cereal, the atta or rice for one meal. NNWA's table of fibre in Indian foods ranks every food in the database, the pages for Bengal gram and guava as a fruit give the full panels, and a separate article covers millets in the Indian diet.

How does a full Indian plate add up?

ICMR-NIN's My Plate for the Day, built for 2,000 kcal, comes to roughly 38 g of fibre when the food-group averages are applied to it. The plate holds 250 g of cereals and millets, 85 g of pulses, 400 g of vegetables, 100 g of fruit and 35 g of nuts and seeds, all raw weights. At 6, 12, 2, 2 and 9 g of fibre per 100 g, those amounts give about 15, 10, 8, 2 and 3 g. This is NNWA's arithmetic on ICMR-NIN's own tables, not a figure the guidelines print, and it assumes cereals at the group average.

The same guidelines ask that at least half of the cereals and millets you eat be whole grain, that every cereal-based meal come with pulses or beans, and that fruit be eaten fresh instead of as juice. A plate that follows those lines clears the 30 g mark without a supplement or a special product.

Too little fibre, and who is at risk in India

Fibre has no named deficiency disease. ICMR-NIN's 2024 guidelines say it is important for proper bowel function and that it reduces constipation and the risk of developing piles. No national survey reports fibre intake directly. The nearest official signal is in the same guidelines: people in India eat only 100 g to 200 g of vegetables and fruit a day against a recommendation of 500 g. Diets built on polished rice, maida and packaged snacks, with fruit taken as juice, are the ones most likely to fall short.

Intake is not low everywhere. Among 929 adults with type 2 diabetes in the Chennai Urban Rural Epidemiology Study, the median fibre intake was 29 g a day, drawn mainly from vegetables and legumes. Those eating less than the median had more high total cholesterol (49.5 per cent against 40.1 per cent) and more high LDL cholesterol (46.2 per cent against 35.5 per cent). The study was cross-sectional, so it shows an association in one city and cannot prove that fibre was the cause.

What does the evidence say about fibre and health?

The evidence is consistent across large reviews, though much of it is observational. A meta-analysis of 22 cohort publications in the BMJ found that each additional 7 g of fibre a day went with a 9 per cent lower risk of both cardiovascular disease and coronary heart disease. Cohort studies follow what people choose to eat, so those who eat more fibre may differ in other ways as well.

In people who already have diabetes, a 2020 systematic review in PLoS Medicine pooled 42 trials with 1,789 adults. Higher fibre intakes lowered HbA1c by 2.00 mmol/mol and body weight by 0.56 kg compared with lower-fibre diets, and cohort data linked 35 g a day, against 19 g, with 14 fewer deaths per 1,000 people. The trial results varied widely and none ran for a year. These are modest shifts in risk markers alongside medical care, not a replacement for it, and the diabetes nutrition course teaches how fibre fits into a full plan.

One Indian trial is worth knowing. In mildly hypercholesterolaemic adults in India, 69 of whom completed the study, 3 g of soluble fibre a day from 70 g of oats lowered total cholesterol by 8.1 per cent over four weeks, against 3.1 per cent on the usual diet, and LDL cholesterol by 11.6 per cent against 4.1 per cent. It was small, short and open-label, and its authors asked for larger and longer studies.

A worked example: a day at 16 g and the same day at 32 g

This is an illustrative case, not a real person. Take a 34-year-old bank officer in Pune with a desk job, for whom ICMR-NIN's adequate intake is 25 g. Her usual day, in raw weights: 60 g of maida as bread at breakfast (1.7 g of fibre), 100 g of rice (2.8 g), 30 g of toor dal (2.7 g) and 100 g of cabbage (2.8 g) at lunch, then 80 g of rice (2.2 g) and 100 g of bhindi (4.1 g) at dinner. Using IFCT 2017 values, the day comes to about 16 g.

Now change three things. The breakfast becomes rotis from 60 g of atta (6.8 g in place of 1.7 g). The lunch dal becomes 30 g of whole moong (5.1 g in place of 2.7 g). The first two changes bring the day to about 24 g, just under her target. Adding one 100 g guava in the afternoon (8.6 g) takes it to about 32 g. Nothing was added to the day except a fruit, and her rice at both meals stayed.

Common mistakes and myths about fibre

The most frequent mistake is counting chapatis and forgetting the dal. Split and washed dals lose much of their fibre with the seed coat: red gram has 22.84 g per 100 g whole and 9.06 g as dal, and green gram falls from 17.04 g to 9.37 g. The second is raising fibre sharply in a single week and then giving up because of gas.

If you do use a husk, the page on how to take isabgol covers the amount of water and the cautions. A related myth is that fibre is only about constipation: the reviews above measured cholesterol, blood glucose, body weight and heart disease.

Is too much fibre a risk, and when should you see a doctor?

ICMR-NIN's 2020 table of tolerable upper limits has no entry for fibre. The usual cost of a quick increase is gas and bloating. In the OmniHeart feeding trial, 164 adults moved to diets with about 30 g of fibre per 2,100 kcal, and the share reporting bloating rose from 18 per cent on their own diets to between 24 and 33 per cent. Going up gradually, with enough fluid, is the practical answer.

Fibre does not replace a medicine for cholesterol, blood glucose or blood pressure, and you should not stop or change a prescription because your diet has improved. A change in bowel habit that lasts, at any age, deserves a medical opinion before a dietary one.

Learning this subject at NNWA

Fibre, whole grains and the reading of food tables are taught at NNWA, a private skill academy in Kolkata whose classes run online in English and Hindi. Its courses, starting with the Certification in Nutrition, prepare people to coach healthy clients on food and to refer medical cases to a doctor. None of them is a degree or a dietitian qualification.