Fibre is something most of us associate with two things: whole grain cereals and going to the bathroom regularly. However, fibre is found in a whole array of delicious food and its many virtues extend to improved heart health, feeling full and satisfied after meals, and keeping your blood sugar stable.
But how much should you actually be eating?
What is fibre?
Dietary fibre is a kind of carb found in plant foods, including whole grains (like oats, barley, and whole wheat pasta), legumes (lentils, beans), nuts, seeds, fruits, and vegetables.
There are two types of fibre. The soluble kind dissolves in water to create a gel like substance; insoluble fibre, however, doesn’t break down at all. Certain foods might be higher in one or the other, but most plant foods usually contain some of both.
We need fibre in our diets for a few reasons. “Fibre is the main source of fuel for the beneficial bacteria in our microbiome,” says Rhian Stephenson, nutritionist, naturopath and founder of Artah Health. “Because we lack the enzymes to break down most dietary fibre, it will pass through the GI tract into the colon relatively unchanged where it is then ‘eaten up’, or fermented. This fermentation process produces compounds that are beneficial to our health, called ‘postbiotics.’”
Probiotics help with everything from reducing inflammation to improving the health of our bodies' cells. “Fibre is also important for blood sugar control, bowel health and our gut barrier function,” Rhian adds.
Insoluble fibre is especially critical in this regard. It helps add bulk to your stool, and accelerates the movement of food through the digestive system to prevent you from getting backed up, according to the FDA.
Soluble fibre actually has the opposite effect: It slows down digestion, which prevents all of the food you eat from being broken down and excreted too rapidly. That’s why you generally want both, so they can sort of balance each other out and keep things regular.
How much fibre do you need?
“Adults want to aim for a minimum of 30g of fibre per day,” says Rhian. “The average adult intake in the UK is 18g, so there's a way to go. The best way to do this is to include a variety of plant-based foods at every meal; this can include vegetables, fruits, nuts, seeds, lentils, beans and whole grains.”
There are also certain foods that pack in a large amount of fibre, adds Rhian. “One cup of cooked beans or lentils can have up to 16g of fibre. In fact, beans are thought to be one of the best 'superfoods' because they have been shown to encourage microbial diversity and improve glucose control.”
There are also lifestyle factors that can affect your fibre requirements in the short or long term. One is your activity level, because exercise can help move digestion along. Another is stress, which can either cause constipation or diarrhoea. And if you eat a lot of ultra-processed food, you'll also have an inadequate intake of fibre. “Ultra-processed foods are naturally quite devoid of fibre,” Rhian notes. “A healthy, exclusively plant-based diet is also reported to have on average twice the fibre as healthy omnivore diets.”
And there are some medical factors to consider, too, such as Crohn’s disease, celiac disease and irritable bowel syndrome (IBS). For instance, people with irritable bowel syndrome (IBS) may find that fibre helps decrease symptoms like bloating, pain, and diarrhoea, according to the Cleveland Clinic, while certain fibrous foods like fruit and broccoli can actually cause bloating and gas. If you are suffering from one of these conditions it's important to talk to your doctor about your fibre needs.
What happens when you get too little fibre?
As you may have unpleasantly experienced at some point in your life, too little fibre can cause digestive issues like constipation. “Adequate fibre intake is very important for regular bowel movements and digestive health,” says Dr Christine Lee, a gastroenterologist at the Cleveland Clinic.
Because the microbiome is implicated in virtually every aspect of our health, Rhian notes that "over time, a diet lacking in fibre can lead to mood disruptions, poor blood sugar regulation and a higher risk of autoimmunity and chronic illnesses.
“If we don't eat enough fibre, we essentially starve our microbes, and when this happens, they turn to the mucosal layer of our gut for fuel,” she continues, “Essentially, they start to 'eat' away at this lining, which is an essential part of our immune system. Studies have shown that the less fibre we eat, the thinner our mucous membrane and higher our levels of inflammation."
Is there such a thing as too much fibre?
While we know that too little fibre is problematic, is there such a thing as too much fibre? Possibly. Some people might experience abdominal discomfort, bloating and gas from eating extremely high levels of fibre, Dr. Lee says. “There are certain individuals who need to go slowly when it comes to increased fibre, like those with IBS and small intestinal bacterial overgrowth (SIBO),” adds Rhian.
And it’s possible that eating too much fibre could interfere with the absorption of minerals like magnesium, zinc, iron and calcium. But because many high-fibre foods are supplying good amounts of these minerals anyway, this isn’t generally an issue, according to the U.S National Library of Medicine.
Answers about vitamins A to Z(inc).
How do you get enough fibre?
You shouldn’t really have to go out of your way to get enough fibre, because a well-rounded and generally healthful diet is also a fibre-full diet.
“Fibre is exclusively found in plants,” says Rhian. “A diet with plenty of beans, lentils, vegetables, nuts, seeds and fruit will naturally be high in fibre. Easy ways to increase fibre are adding seeds (flaxseed, sunflower, pumpkin) to salads, soups, and stir fries. Include beans and lentils often, and ensure you’re having a good serving of vegetables at every meal."
To give you a rough sense of what that variety can actually look like, the NHS has a handy list of the fibre content per serving for a number of different foods. For instance, a lunch made up of a baked jacket potato with the skin on (4.7g) with around half a can (about a 200g portion) of reduced-sugar and reduced-salt baked beans in tomato sauce (9.8g), followed by an apple (1.2g) will give you around 15.7g of fibre. So it can add up pretty fast.
By the way, you generally don’t need to worry about how much of each type of fibre you’re getting either. Like we mentioned, most plant foods have both insoluble and soluble fibre, and most nutrition labels don’t break the fibre content down that way anyhow.
A word on fibre supplements
There isn't any evidence that taking daily fibre supplements is harmful, according to the Mayo Clinic. They're also great if you’re experiencing constipation, Dr. Lee says.
However, overloading on fibre too quickly is easier to do with supplements than whole foods, so the advice is to start slow and drink enough water, Dr. Lee says, because fibre works optimally with water. You also want to make sure you stay hydrated if you want to keep your poop soft and bulky and avoid uncomfortable symptoms like gas, cramping, and bloating.
Plus, some fibre supplements can interfere with the absorption of medications if you take them at a similar time—so take them at a different time of day from each other, and talk to your prescribing doctor before adding functional fibre to your diet. And definitely consult your doctor first if you have a GI condition.
Something else to consider: Relying purely on supplements means you miss out on a rainbow of other nutrients. “While fibre is important, phytochemicals - compounds found in plants - like polyphenols are also important prebiotic substrates for our bacteria,” Rhian says. “These are in green tea, herbs like ginger and turmeric, and dark-coloured fruit and vegetables like pomegranate, cranberry, blueberries, spinach, red chicory and more.” Plus, the real stuff just tastes so much better.
A version of this article originally appeared on Self.
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