How to Read UK Food Labels: A 5-Minute Guide to Sugar, Salt and Saturated Fat
Traffic light labels can tell you a lot about a packet in seconds. Here's how to read sugar, salt and saturated fat at a glance and compare products fairly.
Stand in front of a shelf of pasta sauces and every jar makes the same promise: rich, authentic, made with sun-ripened tomatoes. What the labels don't shout about is that one of those jars holds three times the salt of the one next to it. That information is there, printed in small coloured squares on the front of the pack. Learning to read it takes about five minutes, and it will change what ends up in your trolley far more than the marketing copy ever does.
What the traffic lights are actually telling you
Front-of-pack nutrition labelling is voluntary in the UK, but most supermarkets and the larger food brands use it. You'll see four nutrients listed — fat, saturates, sugars and salt — each with a colour beside it. Green means the product is low in that nutrient, amber means medium, red means high.
The colour refers to 100g or 100ml of the product, not to the portion you're about to eat. That single detail trips up more shoppers than anything else, and it's worth coming back to. Energy is usually listed too, but without a colour, because the traffic light system only covers fat, saturates, sugars and salt.
The numbers behind the colours
If a pack has no traffic lights, or you're looking at a back-of-pack panel, you can apply the same thresholds yourself. These are the standard figures, per 100g:
- Sugars: green at 5g or less, amber above 5g up to 22.5g, red above 22.5g
- Fat: green at 3g or less, amber above 3g up to 17.5g, red above 17.5g
- Saturates: green at 1.5g or less, amber above 1.5g up to 5g, red above 5g
- Salt: green at 0.3g or less, amber above 0.3g up to 1.5g, red above 1.5g
Drinks are measured per 100ml using the same thresholds. Notice how wide the amber band is. A cereal with 6g of sugar per 100g and a cereal with 21g per 100g both show amber, yet they are completely different products. When two items share a colour, read the grams and compare those instead.
Per 100g versus per portion
Per 100g is the only fair way to compare two similar products, because it ignores how much of each one you happen to eat. But per portion is what actually lands on your plate, and the two can tell very different stories.
Olive oil is a good example. It's almost entirely fat, so it will often show red for saturates on a per-100g basis — but you drizzle a tablespoon, not 100g, so the amount you consume is modest. Cheddar behaves similarly: high in saturates per 100g, but a 30g slice is a reasonable portion. Now consider a ready meal showing amber for salt at 1.2g per 100g. That looks moderate until you realise you're eating the whole 400g tray, which adds up to nearly 5g of salt — close to the 6g daily maximum for an adult.
So use the per-portion column, but check that the portion is realistic. If a label calls 30g of cereal a serving and you fill the bowl twice, double every number. The percentage Reference Intake figures are handy here: they show how much of a day's benchmark a portion provides. The adult benchmarks are 20g saturates, 90g total sugars and 6g salt.
Reading the ingredients list
Ingredients are listed by weight, heaviest first, so if sugar or salt appears in the first three, take note. Sugar is often split across several names — glucose syrup, invert sugar, honey, malt extract, fruit juice concentrate — so no single one climbs to the top of the list.
Health claims are regulated, but they only describe one nutrient. "Low fat" means no more than 3g fat per 100g; "reduced fat" means at least 30% less fat than the standard version, which isn't the same as being low in fat. A fat-free yoghurt can still be sweetened heavily, and a "no added sugar" smoothie can carry plenty of naturally occurring sugar.
A quick way to compare two products in the aisle
- Pick up both packs and look at the front-of-pack panel.
- Decide which two nutrients matter most for that type of food. For most savoury products it's salt and saturates; for breakfast cereals, yoghurts and sauces it's sugars.
- Compare per 100g, like for like. This is the only comparison that isn't skewed by portion size.
- Check the per-portion column and the % Reference Intake to see what a realistic serving gives you.
- Glance at the first three ingredients. If sugar or salt is among them, that tells you something the colours can't.
When a red light isn't the whole story
A red light means high in that nutrient per 100g. It doesn't mean the food is off-limits. Cheese, olives, cured fish and many traditional foods are naturally salty or high in saturated fat, and they've been eaten in small amounts for generations. The traffic lights work best as a tool for comparing similar products and for spotting the everyday items where a red light appears without you expecting it — a pasta sauce, a soup, a slice of bread.
Green lights have their own blind spots. A product can be green for fat and still be high in sugar, and low-fat versions of foods often contain more thickeners and sweeteners than the original. Meanwhile, plenty of genuinely good food carries no label at all: fresh vegetables, fruit, plain fish, pulses and unprocessed meat. No coloured squares doesn't mean no nutrition.
One packet rarely decides anything. The pattern of what you buy most weeks matters far more than a single red light, so use the labels to nudge your regular basket rather than to police every individual item.
The five-minute habit worth keeping
You don't need to study every label on every shop. Choose two or three products you buy every week — your bread, your cereal, your pasta sauce, your yoghurt — and compare the brands on the shelf once. Do it properly, per 100g, and you'll usually find a clear winner. Then switch and stop thinking about it.
A simple rule for the rest of the shop: aim for mostly green and amber, treat reds as occasional rather than everyday, and don't let a green light on one nutrient distract you from a red on another. If you're managing a condition such as diabetes, high blood pressure or high cholesterol, or you're shopping for young children, it's worth speaking to your GP or a registered dietitian before making significant changes to your diet.
Photo: reenablack / Pixabay
