Most people have heard 25 grams. Fewer know there is a second figure sitting behind it, and the gap between the two is where the interesting part lives.
The two numbers
25g is the Adequate Intake for adult women. That is the amount that keeps your bowel working comfortably. Men need 30g.
28g is the Suggested Dietary Target. That is a different kind of figure altogether. It is not about regularity, it is the intake associated with lower risk of heart disease, type 2 diabetes and bowel cancer. For men it is 38g.
So one number is about function and the other is about long term risk. They answer different questions, which is why you will see both quoted and why the advice can feel inconsistent.
Where most of us actually sit
Australian adults have a median fibre intake of about 20.7g a day. Women average around 21g.
Only 28.2% of Australian adults meet the Adequate Intake. Fewer than 20% meet the Suggested Dietary Target.
So the average woman is around four grams short of the first number and seven short of the second. That is a real gap, but it is not a chasm, and the size of it matters for what you do about it.
Four to seven grams is one or two additions to what you already eat. It is not a new way of eating.
Soluble and insoluble, without the homework
Fibre gets split into two types, and the distinction is useful up to a point.
Soluble fibre dissolves in water and forms a gel. Oats, barley, legumes, apples, citrus, psyllium. That gel slows digestion, which is part of why a bowl of porridge holds you longer than white toast. It is also the fibre your gut bacteria ferment.
Insoluble fibre does not dissolve. Wheat bran, wholegrains, nuts, seeds, and the skins of fruit and vegetables. It adds bulk and speeds transit.
Here is the part most articles bury: almost every plant food contains both, in varying proportions. An apple has soluble fibre in the flesh and insoluble in the skin. Oats are mostly soluble but not entirely. Legumes carry a good amount of each.
Which means you do not need to track the split. Eating a range of plant foods across a week gets you both without any accounting.
The fibres you do not get much of from food
There is a third grouping worth mentioning, because it cuts across the soluble and insoluble split.
Some fibres are particularly fermentable, meaning your gut bacteria break them down readily. Resistant starch is the best known. It is starch that resists digestion in the small intestine and reaches the large intestine intact, where it is fermented. You get it from cooked and cooled potato and rice, slightly green bananas, and legumes.
Acacia fibre, sometimes called acacia gum, is another. It is a soluble fermentable fibre that is unusually well tolerated, producing less gas than inulin or chicory root at the same dose.
These are the fibre types that are hardest to get a meaningful amount of from ordinary eating, which is why you see them in formulated products. Greenher Daily contains both, for that reason.
When the distinction does matter
There is one situation where it helps to know the difference.
If things are moving too slowly, insoluble fibre and water is the combination that helps, so wholegrains, vegetable skins and adequate fluid.
If things are moving too quickly, soluble fibre can help by forming that gel and slowing transit. Oats, banana, psyllium.
Beyond that, the split is more interesting than useful for most people most of the time.
Why fibre matters beyond digestion
Fibre does a great deal more than keep you regular. It feeds the bacteria in your large intestine, which produce short chain fatty acids that support the gut lining. It slows glucose absorption, which is why what you eat alongside a carbohydrate changes how it behaves. It binds cholesterol. And it adds bulk and slows gastric emptying, which is a large part of why fibre rich meals hold you longer.
There is also a specific reason it matters for women, which we covered in our very first issue. A group of gut bacteria known as the oestrobolome is involved in how oestrogen is metabolised and recirculated, and fibre influences that population. That piece is here if you want it.
The takeaway: 25g is the Adequate Intake for women and 28g is the Suggested Dietary Target for reducing chronic disease risk. Australian women average around 21g, and fewer than one in five adults reach the higher figure. Soluble and insoluble fibre do different jobs, but almost every plant food contains both, so eating a range across a week is enough without tracking the split.
The science behind this post:
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Dietary Fibre. Adequate Intake 25g per day for women aged 19 to 70 and 30g for men. Suggested Dietary Target for chronic disease risk reduction 28g for women and 38g for men. nrv.gov.au
- Fayet-Moore F, Cassettari T, Tuck K, McConnell A, Petocz P (2018). Dietary Fibre Intake in Australia. Nutrients, 10(5), 599. Median adult intake 20.7g per day; 28.2% of adults met the Adequate Intake and fewer than 20% met the Suggested Dietary Target.
- Australian Bureau of Statistics. Australian Health Survey: Usual Nutrient Intakes. Average dietary fibre intake for Australian women aged 19 and over. abs.gov.au
- Food Standards Australia New Zealand. Australian Food Composition Database. Soluble and insoluble fibre content of common plant foods. foodstandards.gov.au