It's the forgotten 'fourth macro' and most of us are only getting around half what we need. Here's why you need it for more than just digestion

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Fibre - are you getting your fill? Chances are, you’re not. The NHS sets a target of 30g a day for fibre intake, but most UK adults clock up only 15 to 18g. Our overly-refined diet is commonly blamed for our poor intake, but supposedly healthy carb-dodging diets such as keto and even the rise in  gluten-free foods  which tend to be more processed and less fibre-rich, have all contributed to our 'roughage deficit.'

“Low carbohydrate diets are ‘trendy’ but not necessarily healthy," says nutritionist   Lily Soutter  By omitting starchy carbohydrates from the diet, a huge proportion of fibre is also omitted which is often why those on low carb diets suffer from constipation.”

It might sound obvious but fibre is a plant-based phenomenon. Meat, fish, eggs and dairy products are all devoid of fibre.

You might think your diet is healthy, but how does it really rate on fibre? Fibre doesn't just keep everything moving, but it's an essential food for your good gut microbes, which play a role not just in gut health but mental health, mood and clear skin.

Low carbohydrate diets have been associated with a change in gut bacteria,says Lily. "This is because fibre is fermented in the large intestine and our gut bacteria use this fibre as fuel to flourish and grow.”

And given that we have more bacteria cells in our body than human cells - yes, we're 50 per cent microbes - it's essential that we give the good guys what they need - otherwise the baddies move in.

You might be surprised to learn that women consume less fibre than men; a recent National Diet and Nutrition Survey revealed that 90 per cent of us of women were consuming 18g of fibre or less per day, compared with 70 per cent of men.

Before you pour yourself a bowl of (surprisingly sugary, FYI) bran flakes, here’s what fibre can do for you, and how to make sure it’s abundant in your diet without resigning yourself to living on Weetabix et al alone.

Fibre helps prevent major diseases

Research suggests that getting your daily quota of fibre can play a part in preventing diseases such as type one and type two diabetes, reduces the risk of heart disease by 40 per cent, decreases your risk of suffering a stroke by seven per cent, reduces the likelihood of bowel cancer in particular, reduces joint pain in arthritis patients, improves sleep quality and helps to prevent obesity while maintaining general digestive health. High five for fibre.

3 types of fibre - and why you need them all

1. Soluble fibre - softens your stool

It's so-called owing to the fact that it dissolves in water, this is the key kind to consider if you’re constipated. Lily explains the process:

“Soluble fibre dissolves in the water within the gut and forms a gel-like substance. This helps to soften stools in order pass smoothly through the bowel. Soluble fibre may also reduce the amount of cholesterol within the blood.”

Sources of soluble fibre: Oats, barley, rye, fruit and root vegetables, beans and pulses with top marks going to flaxseeds.

2. Insoluble fibre - bulks out your stool

This type of fibre doesn’t dissolve in water. “Insoluble fibre passes through the gut without being broken down," explains Lily. "It gives substance to your stool and helps other foods move through the digestive system more easily.”

Sources of soluble fibre: Lily advocates eating wholemeal bread, bran, cereals, nuts and seeds, and stresses that “for optimal health we need a combination of both soluble and insoluble fibre, and many fibre-rich foods contain a mix of soluble and insoluble fibre, but in varying proportions.”

3. Resistant starch - food for your gut microbes

In The Clever Guts Diet , Dr Michael Mosley  gets rather excited about this one, to the extent of setting up his own study. It's low in calories, helps prevent blood sugar spikes and acts s a prebiotic AKA food for your good bacteria helping it thrive.

“Resistant starch is a type of starch that, as its name implies, resists digestion in your stomach and small intestine and reaches your colon largely intact. You are unlikely to get big blood sugar spikes after eating resistant starch, and you won’t hold onto many calories from it either," He says

“Once it reaches the large intestine, it feeds the 'good' bacteria which digest it and release butyrate, a chemical that reduces inflammation and strengthens the gut wall.”

Sources of resistant starch: "You’ll find lots of resistant starch in grains, seeds and legumes," says Dr Mosley. "You also get it in unripe bananas and green peas." You'll also find it in tiger nuts , a superfood popular in Spain (where it's mostly consumed as nut milk) but also sold globally as a chewy snack and as flour.

Eating cooked and cooled pasta and rice is good for you!

One of the more surprising places you’ll find resistant starch is in pasta or rice that have been cooked and cooled. The process "changes the structure of the starch within it, making it more resistant to digestion," says Dr Mosley.

He conducted an experiment with pasta in partnership with the University of Surrey, where volunteers ate pasta hot, cold and reheated. The results were music to the ears of pasta fans. “Volunteers’ blood sugar levels were measured after each meal and we discovered, as expected, that eating cold pasta led to a smaller spike in blood glucose and insulin than eating freshly boiled pasta.”

“But then we found something we didn’t expect - cooling, cooking and reheating the pasta had an even more dramatic effect. Or, to be precise, eating reheated past resulted in an even smaller effect on blood sugar levels than eating cooled pasta. In volunteers, it reduced the rise in blood sugar levels by 50 per cent.”

In short, after a long day, reheating that pasta bake may pay off health-wise as well as time-wise.

Increase your fibre intake gradually

Hitting your system with a whack of fibre could do more harm than good where bloating, cramping and wind are concerned – no one wants that. It’s also important to stay hydrated to help fibre to pass through your system.

Getting your five a day and swapping white, refined carbohydrates for wholegrain and wholemeal options will naturally boost the fibre in your diet too.

1. Swap your bread

Simply changing your bread  can help, says Lily.“White refined carbohydrates have been stripped of their fibrous outer layer. Wholemeal bread for example contains 2.2g fibre per slice, whereas white bread may only contain 0.8g fibre per slice.”

2. Fill half your plate with vegetables at each meal

3. Get fibre at breakfast A daily bowl of porridge or two slices of wholegrain toast can instantly give your breakfast a fibre boost. Bircher muesli (grate the apple, skin on into oats and milk, add almonds, chia, flax etc) or overnight oats work well too.

4. Keep the skin on your  potatoes .

5. Sprinkle fibre-rich seeds over your porridge, salads or avocado on toast.

6. Keep beans, chickpeas and lentils in your cupboard - tinned or dried. They are full of fibre and cheap and easy to cook.

7. Eat high fibre snacks: popcorn, fruit, fruit dipped in nut butter, nuts, seeds, wholegrain crackers with hummus or bean dips.

8. Sprinkle flaxseeds (linseeds) everywhere. Nutritional therapist  Eve Kalinik  advises buying whole golden linseed and grinding up a small put to keep in the fridge to preserve their nutrients. Sprinkle on slags, smoothies, soups. If you're a chia seed fan, these are great for smoothies too.

9. Add baobab powder to your smoothie. “Baobab is nearly 50 per cent fibre, half soluble and half insoluble, so adding a couple of teaspoons of sweet and citrussy baobab powder to a fresh smoothie or stirring through porridge is an easy way to support a healthy gut,” says Eve. it has a sweet citrussy taste most people love. You can even bake with it.

Try Aduna Baobab , from £9.75 for 80g, if that sounds up your alley, and if you’re looking to identify whether a food you’re buying is fibrous, bear in mind that 6g or more of fibre per 100g is considered high fibre.

10. Have leftovers for your lunch - potato salad or even last night's Indian. Rice and lentil dhal work perfectly for your resistant starch quota.

When you actually might not need extra fibre

Going fibre-nuts isn’t for everyone, as Dr Mosley highlights: “If you have a diseases gut, adding more fibre to your diet may actually make you feel worse.”

Similarly, the NHS warns against a willy-nilly approach to fibre if you’re suffering with digestive problems:

“If you have a digestive disorder such as irritable bowel syndrome (IBS) , you may need to modify the type and amount of fibre in your diet in accordance with your symptoms. Your GP or a dietitian can advise you further about this.”

Just on a closing note, if you’re suffering from diarrhoea, the NHS advises limiting the amount of insoluble fibre you consume until you’re better to prevent further gut irritation. Otherwise, go forth and be fibrous.

How healthy is your breakfast cereal, really?

Follow Lily  @LilySoutter , Dr Michael Mosley  @DrMichaelMosley  Eve  @EveKalinik