Carbohydrates and fibre
Tell sugars, starches and fibre apart, see why whole grains beat refined ones, and find easy ways to eat more fibre.
THREE KINDS
Sugars, starches and fibre
- Sugars are the small, fast ones: in fruit, milk, table sugar, honey and dates.
- Starches are long chains of sugar the body breaks down: in rice, bread, potatoes, pasta and legumes.
- Fibre is the part of plants we can't fully digest: the skins, husks and cell walls in whole grains, vegetables, fruit, legumes, nuts and seeds.
Many guidelines put carbohydrates at roughly half of daily energy (the US range is 45 to 65 %). WHO's 2023 guidance puts the weight on the source: whole grains, vegetables, fruit and legumes.
A plate of lentil rice holds all three: a little sugar, a lot of starch, and a good dose of fibre from the lentils.
Check yourself
Which kind of carbohydrate is each of these mainly?
- Honey
- Plain boiled rice
- Wheat bran
- The natural sugar in milk
- A boiled potato
- The skin of an apple
Show the answer
Sugars: Honey, The natural sugar in milk
Starch: Plain boiled rice, A boiled potato
Fibre: Wheat bran, The skin of an apple
INSIDE A GRAIN
Whole grain versus refined grain
A grain of wheat or rice has three parts: the bran (the outer skin, full of fibre), the germ (the small seed with vitamins, minerals and healthy fats) and the endosperm (the starchy middle). A whole grain keeps all three. Refining strips the bran and germ away, and with them most of the fibre and some vitamins and minerals, leaving mostly starch.
Brown rice, oats, and bread made from wholemeal flour, like a good sangak, are whole grain. White rice, white flour and most white bread are refined.
Check yourself
When wheat is refined into white flour, which parts of the grain are removed?
- Only the endosperm
- The bran and the germ
- Nothing, it's just ground finer
- Only the germ
Show the answer
The bran and the germ
Right. Refining removes the bran and germ, and with them most of the fibre and some vitamins and minerals. What's left is mostly the starchy endosperm.
What happens after you eat
Refined starches and sugars
White bread, white rice, sweets and sugary drinks are digested fast. Blood sugar rises quickly and falls again, and hunger often comes back sooner.
Whole grains, legumes and fibre
The fibre and intact structure slow digestion down. Blood sugar rises more gently, and you tend to stay full for longer on the same amount of energy.
Check yourself
Arash wants his breakfast to be a whole grain. Which should he choose?
- White rice
- Oats
- A pastry made with white flour
- Cornflour porridge
Show the answer
Oats
Yes. Oats are eaten as a whole grain, with the bran and germ still in them.
Dietary fibre
The parts of plant foods your gut can't fully break down. It keeps digestion regular and feeds the helpful bacteria in your gut, and higher intakes are linked to a lower risk of heart disease, type 2 diabetes and bowel cancer. WHO (2023) recommends adults get at least 25 g a day from food; UK advice is 30 g. Most adults eat well below this.
Fruit juice has almost none: the fibre stays in the pulp and skin that juicing removes.
Building a day to 25 g of fibre (all about):
breakfast 40 g oats 4 g
snack 1 medium apple, with skin 4 g
lunch lentil soup (100 g lentils) 8 g
2 slices wholemeal bread 5 g
dinner 2 handfuls of vegetables 4 g4 + 4 + 8 + 5 + 4 = about 25 g.No special foods, just whole versions of ordinary ones. Swap the soup for a bowl of chickpeas, or the apple for a pear, and the total barely changes.
Check yourself
What is WHO's minimum daily fibre recommendation for adults?
- At least 5 g
- At least 25 g
- At least 100 g
- There is no recommendation
Show the answer
At least 25 g
Right. WHO (2023) recommends at least 25 g of naturally occurring fibre a day; the UK suggests 30 g.
Three common mix-ups
- "Carbs are fattening." Extra energy from any source is stored over time; carbohydrate isn't special. Whole-grain and legume carbs tend to fill you up more.
- "Brown means whole grain." Colour can come from caramel or malt. Check the ingredients list says whole grain or wholemeal flour first.
- "Juice counts as fruit fibre." Juicing leaves the fibre behind. Eat the fruit; drink water.
Check yourself
A glass of apple juice gives you about as much fibre as eating an apple.
Show the answer
False
False. A medium apple with its skin has about 4 g of fibre; a glass of clear apple juice has almost none, because the pulp and skin are left behind. Juice also delivers its sugar faster.
Lesson recap
- Carbohydrates are the body's main everyday fuel, in three kinds: sugars, starches and fibre.
- A whole grain keeps its bran, germ and endosperm; refining strips the bran and germ, and most of the fibre with them.
- Refined carbs are digested fast; whole grains, legumes and fibre raise blood sugar more gently and keep you full longer.
- WHO recommends at least 25 g of fibre a day; oats, fruit, lentils, wholemeal bread and vegetables get you there.
- Check labels for "whole", eat fruit rather than juice, and add fibre slowly with water.