Eat 30 grams of fiber every day

Why fiber deserves a place on your plate

Many adults in wealthy countries eat well under 20 grams of fiber a day. Most health guidelines suggest about 25 to 30 grams, so the gap is real. Refining grains strips away the bran and germ, which is where much of their fiber sits. That is why a day of white bread, white rice and packaged snacks can feel filling and still fall short.

The gap is fairly easy to close. A bowl of oats, a few spoonfuls of beans or an apple with its skin each adds several grams. You don't need special products or supplements, and a fiber food at every meal gets you most of the way.

How fiber works in your body

Fiber comes in two main kinds. Soluble fiber, found in oats, beans and many fruits, dissolves in water and forms a soft gel in your gut. This gel slows how quickly sugar from a meal reaches your blood. It also carries away some bile acids, which your liver then remakes using cholesterol.

Insoluble fiber, found in whole grains, nuts and vegetable skins, adds bulk and helps food move through your bowel. Some fiber also feeds the bacteria in your large intestine, which turn it into small compounds that nourish the cells lining your colon. These are the reasons researchers expect fiber to matter, while the studies below measured health results directly.

What the research found

In 2019, a team led by Andrew Reynolds pooled about 185 long-term studies and 58 trials for the World Health Organization. People who ate the most fiber had 15 to 30% lower rates of death, heart disease, stroke, type 2 diabetes and bowel cancer than those who ate the least. The largest risk reductions appeared at about 25 to 29 grams a day, and the trend hinted that a little more might help further. In the trials, eating more fiber led to slightly lower body weight, blood pressure and total cholesterol.

An earlier review in the BMJ linked each extra 7 grams a day to a 9% lower risk of cardiovascular disease. A meta-analysis of trials found that soluble fiber from foods like oats and beans lowered LDL cholesterol by a small amount. One limit is worth knowing: most of the big numbers come from studies that followed people over time, so they show links rather than proof. People who eat more fiber may also smoke less or move more.

Making it stick

Spread fiber across your day instead of loading it all onto dinner. If your breakfast, lunch and dinner each start with a fiber food at every meal in mind, plus one fiber-rich snack, you cover most of the target without much counting. Oats at breakfast (about 4 g), lentil soup at lunch (8 g), an apple (4 g), broccoli with brown rice at dinner (about 8 g) and popcorn later (3.5 g) come to roughly 28 grams. Keep a tin of beans in the cupboard, where it will wait patiently for the night you swear there is nothing to eat.

If you eat little fiber now, build up over two or three weeks and drink plenty of water, since a sudden jump can cause bloating. More is not always better on day one, and supplements aren't needed when food does the job. If you have a bowel condition, or pain, bloating or changes in your bowel habits that don't settle, see a doctor or dietitian. On a busy day, a piece of fruit with the skin on still counts, and soon you become someone who reaches for the whole grain loaf without thinking. Which meal tomorrow already has room for a handful of beans or a slice of whole grain bread?

References

• Reynolds, A., et al. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, 393(10170), 434-445. doi.org/10.1016/S0140-6736(18)31809-9
• Threapleton, D. E., et al. (2013). Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ, 347, f6879. doi.org/10.1136/bmj.f6879
• Brown, L., et al. (1999). Cholesterol-lowering effects of dietary fiber: a meta-analysis. The American Journal of Clinical Nutrition, 69(1), 30-42. doi.org/10.1093/ajcn/69.1.30