Everywhere you turn, all you hear is that you should eat a high fiber diet, and especially if you’re constipated.

Big news out of the United Kingdom. Much of the media coverage of the British Dietetic Association’s guidelines has focused on advice to eat kiwifruit every day.

Meanwhile, other recommendations have not received so much attention. One, in particular, marks a shift in managing chronic constipation. The guidelines don’t advise a high-fiber diet. Read that again to make sure you read it correctly.

Here is what the guidelines say does and does not help with chronic constipation.

What did the guidelines study?

Researchers looked at 75 clinical trials to make recommendations about food, drinks, and supplements for adults with chronic constipation.

The quality of the trials was different, so they had to agree on how strong the evidence was.

Constipation means different things to different people, so the researchers used a broad definition. It included what patients said felt like constipation, as well as definitions used in studies. Chronic constipation is usually when someone passes a few hard stools for at least three months.

The researchers made 59 recommendations. But they said most were based on weak evidence.

Why kiwifruit? How many a day?

The researchers said to eat two to three kiwifruit a day for at least four weeks to help constipation. It doesn’t matter if they are green or gold—both help.

There are a few reasons why.

Fiber in kiwifruit swells a lot when mixed with water, even more than apple fiber. This makes stools bulkier and easier to move through the gut.

Eating the skin gives more fiber, but eating only the inside is fine too.

Green kiwifruit has an enzyme called actinidin that helps the body break down protein in the stomach and small intestine. This may help make food softer and easier to pass.

Kiwifruit also have crystals called raphides, which may help the gut make more mucus. This can help stools move more smoothly.

They may also lower the amount of methane-producing bacteria, which have been linked to constipation.

Mineral water and magnesium

The researchers said drinking mineral water can help. They suggested drinking 0.5–1.5 liters a day (about two to six cups) for two to six weeks.

Mineral water often has magnesium, which works like a laxative. Magnesium oxide is also used as a supplement for chronic constipation.

The guidelines say magnesium oxide can soften stools and help you go more often. They recommended 0.5–1.5g a day for at least four weeks.

But it’s not right for everyone. People with kidney disease need to be careful, and magnesium can interact with some medicines.

Rye bread

Studies showed rye bread helps constipation more than white bread or common laxatives.

The researchers suggested six to eight slices of rye bread a day for at least three weeks.

But this amount is not realistic for many people. And people with celiac disease cannot eat rye because it has gluten.

A high-fiber diet may not be needed after all

One surprise in the guidelines was the weak evidence supporting a general high-fiber diet (25g or more of fiber a day) for constipation.

Researchers found only one high-quality trial comparing a high-fiber diet (25–30g/day) to a low-fiber diet (15–20g/day).

The trial showed no benefit from the high-fiber diet. In fact, people on the low-fiber diet farted less and were less bloated.

This does not mean fiber never helps constipation. There is strong evidence that fiber supplements can help.

But instead of pushing a high-fiber diet, the guidelines recommend taking at least 10g a day of a fiber supplement like psyllium.

High-fiber diets are still important for general health. For example, the Dietary Guidelines for Americans suggest adults get at least 28g a day. Fiber can lower cholesterol and blood sugar.

But now we know a high-fiber diet is not needed to treat chronic constipation.

What can we learn from the guidelines?

These guidelines give more personalized, evidence-based advice based on a person’s symptoms.

Kiwifruit are considered safe and helpful for chronic constipation. Mineral water, magnesium supplements, and rye bread can help too.

But it’s important to talk to a health professional before taking magnesium supplements, especially if you have kidney disease or take other medicines.