Fiber, once synonymous with 1970s diets and bran cereal, is staging a comeback. Yesterday, the online supermarket Ocado reported that sales of prunes have increased by 60 percent in the past year and spelt by 59 percent.
The increase is being driven by younger consumers, with the online supermarket finding 62 percent of Gen Z shoppers were trying to up their fiber intake, compared with 36 percent of over-65s. On TikTok videos about #fibermaxxing—meeting or exceeding fiber consumption guidelines—have gone viral, with high-fiber recipes notching up millions of views.
Given the average adult is fiber-deficient, and fiber is essential for everything from heart to gut health, this is largely a welcome development. However, an increasing and lucrative array of fiber-added shakes, snacks, and cereals on the market are not always as virtuous as they would have us believe.
“Fiber is critical, but food manufacturers are jumping on the bandwagon by sticking a ‘high fiber label’ on ultra-processed foods [UPF] which aren’t necessarily supportive to our health,” says the nutritionist Laura Southern, founder of London Food Therapy. So what should we eat to increase our fiber intake? And what should we avoid?
Is there such a thing as too much fiber?
According to the British Dietetic Association, the average adult’s fiber intake is 18g a day—just 60 percent of the 30g government guideline. Yet some proponents of “fibermaxxing” suggest we exceed the official recommendations. This is unlikely to be dangerous but a sudden increase in consumption will probably lead to bloating, excess gas and sluggishness, while extreme amounts such as 100g consumed without adequate water “could lead to obstruction in the bowel,” says Southern, who believes 25g to 30g a day, an amount linked to a reduced risk of bowel cancer, heart disease and Type 2 diabetes, is “a good number to aim for.”
Make sure you get your fiber from multiple sources
Fiber is either “insoluble”—in foods such as brown rice and nuts, passing straight through the body to support the digestive process; or “soluble”—in fruits and chia seeds, meaning it dissolves in water in the stomach and can delay the stomach emptying to increase satiety.
If you’re just eating wheat bran—the most commonly added fiber in processed foods, and mostly insoluble—“you risk crowding out more nutritious sources of fiber such as vegetables,” Southern says, adding that there is some evidence that phytates (naturally occurring compounds found in most fiber) can bind to minerals, interfering with their absorption into the bloodstream. “So if you’re on a very high fiber diet and, say, taking iron supplements for anemia, there’s a slight risk you won’t absorb the extra iron adequately.”
Swap “high-fiber” breakfast cereals for simple oats
Cereals are not necessarily the best way to boost fiber due to their typically high sugar content. Even Kellogg’s All-Bran, which is high in fiber (27g fiber per 100g) has 18g per 100g of sugar. Kellogg’s Special K High Fiber Golden Clusters contain 13g fiber per 100g—or 5.9g per 45g bowl—“which for me isn’t enough to warrant the 18g sugar per 100g and additives it also contains,” Southern says. Kellogg’s Fruit ‘n Fiber—sales of which have increased at Ocado by 52 percent in the past year—contain less fiber (9g per 100g) and more sugar (24g per 100g) than even the Special K cereal because of its high dried fruit content. Far better, Southern says, is to make porridge with oats, “a soluble form of fiber shown to help lower cholesterol and regulate blood sugar balance.”
Steer clear of high-fiber sweet snacks—browse on fresh fruit instead
When you’re short on time, a high-fiber snack might seem a sensible option, and, with the global high-fiber food market expected to grow from $15 billion in 2023 to $25 billion in 2032, according to the market research firm Data Intelo, there’s plenty of choice. But products such as Fiber One 90 Calorie Chocolate Fudge Brownies (6.1g fiber per 24g brownie) have “very little good to say about them,” Southern says. “The brownie doesn’t have a single healthy ingredient in it, with a high sugar content and emulsifiers known to be bad for gut health. You’d be far better off eating a pear, which has the same amount of fiber and no added chemicals.” Dried prunes (9.4g fiber per 100g), figs (12.1g fiber per 100g), and dates (8.7g fiber per 100g) are high in fiber and natural, so not a bad snack choice, she adds, but easy to binge on and high in sugar. “Try to stick to three fruits per serving.”
Choose a multi-grain seeded loaf over white bread with “added fiber”
For parents with fussy kids, sliced white bread with added fiber can seem a good solution. Hovis White ‘n Fiber contains 1.7g fiber per slice; Kingsmill Mighty White Thick Bread with Wheat Fiber is 1.6g per slice. “This is obviously better than an ordinary sliced white loaf, but is still UPF and contains emulsifiers shown to damage the gut microbiome,” Southern says. And, she says, the added fiber in white loaves is usually wheat bran, while a multigrain loaf will also contain fiber from whole wheat, rye, oats, and barley, a variety “which is better for our gut microbiome, which feed on fiber and give off waste products called short-chain fatty acids, that support our digestive system and reduce inflammation.”
Don’t bother with fiber drinks; choose kombucha if you want a change from water
Yes, a high-fiber drink is better than downing a can of champagne. A 250ml can of The Gut Stuff fiber pop contains an impressive 10g of fiber, for example. “But it also contains 8g sugar,” Southern says. “Does the harm from the sugar outweigh the benefit of the fiber? I think it probably does.”
A better option would be Get More Vits Peach & Apricot Fiber Drink (6g fiber and no sugar per 500ml serving), which, Southern says, could be “a gentle way of increasing fiber intake for someone who is constipated and finding high-fiber foods are causing more bloat. But there shouldn’t be any need for expensive fiber drinks.” Hydration is key to a high-fiber diet (according to the NHS, men should aim for about 2.5 liters of water a day; women 2 liters) and if you find water boring, Southern suggests, try kombucha—a probiotic that supports gut microbes.
Make canned beans a cupboard staple and swap white rice for quinoa
As well as being high in soluble and insoluble fiber, legumes are a great source of protein, and in their canned form, the height of convenience when you’re pushed for time. Stock up on kidney beans (6.1g fiber per 100g), cannellini beans (5.8g fiber per 100g) and chickpeas (5.2g per 100g.) “They’re cheap and versatile,” Southern says. “Blend chickpeas with olive oil and lemon juice to make hummus and throw a can of kidney beans into ratatouille.”
She does warn, though, that legumes contain sugars that can cause bloating. “If you’re not used to eating them, start slowly and build up your consumption.” Replace white rice with quinoa in curries or opt for buckwheat noodles (4g per 100g) over white pasta. “Quinoa has more fiber than even brown rice and is a good source of protein.”
A supplement might be worth the cost
Studies have shown a fiber supplement can not only improve gut health but lower cholesterol and support weight loss. A 2022 systematic review in the journal Nutrients found overweight and obese participants in 27 randomized controlled trials showed “a significantly higher reduction in body weight compared to control groups.”
Most supplements contain psyllium, made from the husks of psyllium seeds. Thanks to comparisons with GLP-1 weight loss drugs, they’ve notched up hundreds of thousands of views on TikTok—when gut bacteria feed on such supplements they produce short-chain fatty acids that can stimulate the release of the GLP-1 hormone, prompting feelings of satiety.
Guar gum is another supplement ingredient, containing prebiotic fiber, that feeds bacteria in the large intestine, and has been shown to reduce cholesterol in the British Journal of Nutrition. “Take a supplement in powder or capsule form, and avoid overly processed supplements such as gummies,” Southern says.
Antonia Hoyle is a London-based freelance journalist whose work has appeared in the Daily Mail, The Mailon Sunday, The Telegraph, the Daily Mirror, Grazia, and Marie Claire, among other publications
