Are carbs bad for you? Good carbs vs refined carbs explained
Few foods have been argued about as much as carbohydrates. In South Africa we lived through the banting years, when bread and pap became the enemy. Before that, we were told to make starch the base of every meal. So which is it?
The short answer: it depends which carbs. This is the first article in our carbs series, and it sets out what the biggest studies and the official guidelines actually say.
A note from Candy
I started Health Nut in 2016, right in the middle of the banting years. Our first product, Restore, found a home with a lot of low-carb eaters, and many of our recipes are keto. We still think low-carb can be a useful tool for some people. But the more research I read, the clearer it became that the question isn't "carbs or no carbs". It's which carbs, and how much. That's what this series is about.
What carbs actually are
Carbohydrates come in 3 main forms:
- Sugars: in fruit, milk, honey, and added sugar in sweets, cold drinks and sauces.
- Starches: in grains (maize, wheat, rice, oats), potatoes, sweet potatoes and legumes.
- Fibre: the part of plant foods your body can't fully digest. It feeds your gut bacteria, slows down how fast sugar reaches your blood and keeps you full.
Your body breaks sugars and starches down into glucose for energy. Fibre is the odd one out, and as you'll see, it's the part that matters most.
Good carbs vs refined carbs
The difference comes down to how much of the original food is left.
| Whole or minimally processed | Refined |
|---|---|
| Oats, brown rice, whole-wheat bread and pasta, coarse or unsifted maize meal, samp | White bread, white rice, white pasta, super maize meal, most breakfast cereals |
| Beans, lentils, chickpeas, split peas | Biscuits, pastries, cakes |
| Whole fruit, vegetables, potatoes and sweet potatoes with skin | Cold drinks, fruit juice, sweets, added sugar |
Refining strips out most of the fibre and many of the vitamins and minerals. What's left is digested fast, so blood sugar rises quickly and you get hungry again sooner. (South Africa adds some vitamins and minerals back into bread flour and maize meal by law, but not the fibre.)
What the biggest studies found
Fibre and whole grains protect. A 2019 series of reviews in The Lancet, commissioned by the World Health Organization, pooled 185 long-term studies and 58 clinical trials. People who ate the most fibre had a 15 to 30% lower risk of dying early, and of heart disease, stroke, type 2 diabetes and bowel cancer, than those who ate the least. The biggest benefit came at 25 to 29 g of fibre a day. Whole grains showed similar results. Most people worldwide eat less than 20 g.
Large amounts of refined grains are linked with harm. The PURE study followed nearly 150,000 people in 21 countries, including South Africa, for about 9.5 years. Those eating the most refined grains (about 7 servings or more a day) had a 27% higher risk of dying and a 33% higher risk of a major heart event than those eating the least. Whole grains showed no such link.
Very low and very high carb intakes both look worse than moderate. A 2018 study in The Lancet Public Health combined data on over 430,000 people. The lowest risk of death was at about 50 to 55% of energy from carbs. Below 40% and above 70% both carried higher risk. Crucially, low-carb diets that replaced carbs with mostly animal fat and protein were linked with higher risk, while those built on plant fats and proteins (nuts, seeds, vegetables, whole grains) were linked with lower risk.
The honest caveat: the PURE and 2018 studies are observational. They show strong, repeated patterns, not proof that carbs alone caused the results, because people who eat differently also live differently in other ways. The fibre evidence is stronger, because the trials and the long-term studies point the same way.
What the official guidelines say
World Health Organization (2023): carbohydrates should come mainly from whole grains, vegetables, fruit and pulses. Adults should aim for at least 400 g of fruit and vegetables and at least 25 g of naturally occurring fibre a day. WHO has long said that a wide range of carb intake can be part of a healthy diet; what matters most is quality.
South Africa's food-based dietary guidelines: "make starchy foods part of most meals", choosing unrefined or whole-grain options such as brown bread, brown rice, oats and coarse maize meal over refined ones.
Notice what neither says: eat as much starch as you like, or cut carbs out completely.
So where does low-carb fit?
Low-carb eating isn't wrong. For people with type 2 diabetes, cutting carbs is 1 of the 2 things shown to lower blood sugar in trials. We explain the evidence in Supplements and type 2 diabetes: what lowers blood sugar. Many people also find low-carb helps them lose weight in the short term.
But for most people, the carbs most worth cutting are the refined ones: sugary drinks, sweets, white bread and pastries. That's where the evidence of harm is strongest. Our guide How much sugar is too much? shows where sugar hides on South African labels. Cutting out beans, oats, fruit and vegetables along with them means losing the fibre that does you good.
What this means on your plate
- Swap, don't just cut. Brown or seeded bread for white, oats for sugary cereal, brown rice or samp and beans for white rice.
- Aim for 25 g of fibre a day. A bowl of oats, a portion of beans or lentils, and 5 portions of fruit and vegetables gets most people there.
- Cut sugary drinks first. It's the single biggest change for most people.
- Pair carbs with protein and vegetables. It slows the rise in blood sugar and keeps you full longer.
- Watch the portion, not just the type. Even good carbs add up if the plate is mostly starch.
Protein with your carbs
Adding protein to a carb-heavy breakfast keeps you fuller for longer. A scoop of our collagen peptides stirs into oats, coffee or yoghurt and adds about 9 g of protein with 0 g of carbs. See the collagen range → Free delivery on orders over R800.
Frequently asked questions
Do carbs make you gain weight?
Weight gain comes from eating more energy than you use, from any source. Refined carbs make that easier because they're quick to eat and don't fill you up for long. In trials, whole grains were linked with slightly lower body weight.
Is bread bad for you?
It depends on the bread and how much. A slice of whole-wheat or seeded bread is a very different food from white bread with added sugar. See What's really in supermarket bread and pasta?
Is fruit too sugary?
No. Whole fruit comes with fibre, and eating it is linked with better health. Juice and smoothies are different, because the fibre is broken down or gone.
Should I go keto?
It can help some people, particularly with type 2 diabetes, but it isn't necessary for good health, and it's hard to get enough fibre on it. If you have a medical condition or take medicine, talk to your doctor first.
More in this series
- How refined carbs affect your blood sugar, energy and cravings
- What's really in supermarket bread and pasta?
- How many carbs do you need, and does it change with age?
- Simple carb swaps that work in a South African kitchen
Got a carb question you'd like answered in this series? Email us at info@healthnutrition.co.za. Your questions help us choose what to write about next.
The sources
- Reynolds A et al. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet 393:434–445. View →
- Swaminathan S et al. (2021). Associations of cereal grains intake with cardiovascular disease and mortality across 21 countries in the PURE study. BMJ 372:m4948. View →
- Seidelmann SB et al. (2018). Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. Lancet Public Health 3:e419–e428. View →
- World Health Organization (2023). Carbohydrate intake for adults and children: WHO guideline. View →
- Vorster HH (2013). "Make starchy foods part of most meals": a food-based dietary guideline for South Africa. South African Journal of Clinical Nutrition 26(3 Suppl):S28–S35. View →
Find out more
- How much sugar is too much? Daily limits, hidden sugars and how to cut back
- Supplements and type 2 diabetes: what lowers blood sugar, what doesn't
- Collagen on a keto diet: what it adds, and what it doesn't
- Food additives: what the evidence says about 5 you'll see on labels
This article is general information, not medical advice. If you have diabetes or another condition affected by diet, or you take medicine that affects blood sugar, speak to your doctor or a registered dietitian before changing how you eat.
About the author
Candy Hamilton is the owner of Health Nut, which has supplied collagen to South African homes and health shops since 2016. She holds a Certificate in Human Nutrition from Health Academy Australia (2020) and writes the research summaries on this site. Every study cited is linked so you can read it yourself. More about Health Nut →
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