How much fibre do I need and why?
Aiming for 25 to 29 grams of fibre per day is well supported and delivers the greatest health benefit. Most people in Western countries fall well short of that, so eating more vegetables, legumes and wholegrain products is a smart step for almost everyone.
Eating 25 to 29 grams of fibre per day is well supported by evidence: people who reach that amount have a 15 to 30% lower risk of early death, cardiovascular disease, stroke, type 2 diabetes and colorectal cancer than people who eat the least. This is shown by large population studies. There are also indications that eating somewhat more provides additional benefit.
The official guideline is 14 grams per 1,000 kilocalories, which for most adults works out to 25 to just over 30 grams per day. On average, people in Western countries eat less than half of that, mainly because heavily processed products contain almost no fibre. The easiest way to reach 25 to 29 grams is through a varied intake of wholegrain products, legumes, vegetables and fruit: for nearly all goals, this is better than a supplement containing a single type of fibre. Supplement labels use terms such as 'voedingsvezel' or 'dietary fibre', sometimes followed by the specific type.
The type you choose does matter. If you want to improve bowel regularity, you can try psyllium or polydextrose: 10 to 15 grams per day for at least 4 weeks. Look on the label for 'psyllium husk' or 'polydextrose'. Make sure to drink plenty of water alongside them. Fermentable fibres such as inulin also appear on many labels, but they do not help with constipation and can sometimes even make it worse. The 'sticky' soluble fibres are responsible for improving cholesterol and stabilising blood sugar: beta-glucan (found in oats) and psyllium. Fibres such as inulin feed beneficial gut bacteria like Bifidobacterium, but whether that alone produces measurable health gains has not yet been sufficiently proven.
For weight management, depression or as a standalone treatment for type 2 diabetes, fibre supplements have been too little studied to recommend: the evidence simply is not there. Whether a supplement is labelled 'prebiotic' or happens to be trending is beside the point. Which specific type of fibre offers the most protection against cancer or cardiovascular disease is also something that current research cannot yet answer. What does count is the total amount over a longer period of time, obtained through real food.
Evidence based on population studies, an umbrella review (>17 million people) and controlled clinical trials. No experimental studies in humans that definitively prove causality for all outcomes, but the association is robust and widely supported.
How many fruits and vegetables do I actually need per day?
Five portions of fruit and vegetables per day (two pieces of fruit, three serving-spoon scoops of vegetables) is the number with the strongest evidence base; eating more does not provide additional benefit, but most people do not even reach this minimum.
How much iron do you need per day?
For healthy adults without a deficiency, 1 to 2 mg of iron per day through food is sufficient. When a deficiency or anaemia is confirmed, requirements are much higher; discuss that with your doctor.
How many vegetables do you really need per day?
Five servings of vegetables and fruit per day offers the best protection, with non-starchy vegetables counting and juice and potatoes not. More than five servings adds nothing.
How much water do I really need to drink per day?
There is no magic number: for a healthy adult who is not very active, thirst is a reliable guide, with a total fluid intake of roughly 2 to 3 litres per day from all sources as a reference point. Drink more as soon as you exercise, when it is warm, or as you get older.
Can you strengthen your immune system by eating more fibre?
Eating more fibre has a clear biological mechanism, but in healthy people it does not automatically lead to a measurably stronger immune system. Fermented foods appear to work more reliably for your gut flora; probiotic supplements are even risky in the context of immunotherapy.
Does eating more fibre help against high blood sugar?
Water-soluble fibre from legumes, vegetables and fruit probably helps lower high blood sugar, but the overall composition of the meal also plays a role. For type 2 diabetes and gestational diabetes, consulting a doctor is always necessary.