Food Labels Decoded

A supermarket shelf is a wall of competing claims, and the least glamorous part of the pack is almost always the most honest. Behind the front-of-pack graphics sit a legally defined nutrition table and an ingredients list ordered by weight, and once you can read those two things fluently you can assess any product in about fifteen seconds. This guide walks through what each element means, which numbers per 100g are genuinely worth memorising, and how marketing language is engineered to steer you away from the small print.

Where to look first on a pack.

Front-of-pack design exists to sell; back-of-pack information exists because the law requires it. Start at the back. In the UK, prepacked foods must carry a nutrition declaration giving energy in kilojoules and kilocalories plus fat, saturates, carbohydrate, sugars, protein and salt, always expressed per 100g or per 100ml. That per-100g basis is the single most valuable feature of the whole system, because it lets you compare two products directly regardless of pack size or how the manufacturer has chosen to define a serving.

Manufacturers may additionally give values per portion, and this is where interpretation gets slippery. A pizza described as two servings, a 500ml bottle labelled as two portions, or a bag of crisps split into three notional handfuls all make the numbers look reassuring. Ask yourself honestly how much you will eat, then do the multiplication.

Directly beneath or beside the table sits the ingredients list, in descending order of weight, with allergens emphasised in bold. Any ingredient named or shown in the product name must also have its percentage declared, which is why a chicken and mushroom pie will tell you it contains, say, 22 per cent chicken. Together, the table and the list answer nearly every question worth asking. The colourful claims on the front answer none of them, and are designed to make you feel you have already assessed the product.

Reading the nutrition table per 100g.

A small set of thresholds turns the table from data into judgement. Broadly, per 100g of solid food: fat is high above 17.5g and low at or below 3g; saturates are high above 5g and low at or below 1.5g; total sugars are high above 22.5g and low at or below 5g; and salt is high above 1.5g and low at or below 0.3g. For drinks the thresholds are roughly halved. Fibre is not colour-coded but is worth seeking out, and anything above about 6g per 100g counts as a high-fibre food.

Put those to work on a worked example. Compare two tomato pasta sauces. Sauce A gives, per 100g, 3.1g sugars and 0.5g salt. Sauce B gives 9.6g sugars and 1.4g salt. Both look similar in the jar, but across a family portion of 250g each, Sauce B contributes roughly 3.5g of salt against Sauce A’s 1.25g, against a daily maximum of 6g for adults. That single swap is more consequential than most supplement decisions.

A second example: two breakfast cereals. One gives 4.2g sugars, 10.6g fibre and 0.1g salt per 100g; the other gives 24g sugars, 3.5g fibre and 0.9g salt. Both are fortified, both marketed as part of a balanced breakfast. The fibre and sugar columns tell you everything the packaging works hard to obscure.

Traffic lights, reference intakes and portion arithmetic.

Front-of-pack colour coding in the UK is voluntary but widely adopted, and it applies exactly the thresholds above to fat, saturates, sugars and salt, usually per portion. Red means high, amber medium, green low. The design intent is not that red foods are forbidden but that a basket dominated by reds warrants a rethink. Used quickly, the colours are a decent triage tool; used carelessly, they mislead, because a tiny declared portion can turn a red into an amber without changing the food at all.

Alongside the colours you will see reference intakes, previously called guideline daily amounts. These are based on a notional average adult consuming 2,000 kcal a day, with 70g fat, 20g saturates, 90g total sugars, 260g carbohydrate, 50g protein and 6g salt. They are a labelling convention, not a personal target. Your own energy needs may be considerably higher or lower depending on body size, age and activity, and the free-sugars recommendation is stricter than the 90g figure suggests.

On sugars specifically, the table gives total sugars, which lumps together the naturally occurring lactose in milk and fructose in fruit with added sugars. WHO and UK guidance both focus on free sugars, recommending no more than around 5 per cent of energy, roughly 30g a day for adults. To estimate free sugars, cross-check the total against the ingredients list: if sugar, syrup, honey or fruit juice concentrate appear, most of that total is free sugar.

The ingredients list tells the real story.

Descending order by weight makes the list quietly revealing. If sugar appears in the first three ingredients of a savoury sauce, or if flour arrives after palm oil in a biscuit, you know the product’s true composition regardless of the marketing. A wholemeal loaf should begin with wholemeal flour; a bread that begins with ‘wheat flour’ and lists wholemeal further down is predominantly white with some wholemeal added, whatever the brown packaging implies.

Sugar has an unusually large vocabulary, and splitting it across several names pushes each one further down the list. Watch for sucrose, glucose, glucose-fructose syrup, invert sugar syrup, dextrose, maltose, maltodextrin, molasses, treacle, honey, agave, rice syrup, fruit juice concentrate and evaporated cane juice. Combined, they can dwarf ingredients listed above them. Similar logic applies to fats appearing as palm oil, palm fat, shea and hydrogenated or partially hydrogenated oils, the last of which is a good reason to choose something else.

Additives are less alarming than their reputation. E numbers are simply approved additives with an identifying code, covering things as ordinary as vitamin C, or ascorbic acid, and beetroot red. A long additive list is nonetheless a reasonable proxy for a heavily formulated product, and diets dominated by such products are consistently associated with poorer outcomes. Look also for the meat content percentage in pies, sausages and ready meals, and for ‘mechanically separated meat’, which indicates a lower-grade input.

Salt, sugar and the numbers worth remembering

Adults should have no more than 6g of salt a day, equivalent to about 2.4g of sodium, and children less: around 2g for one to three-year-olds rising to 6g by age eleven. Most UK salt intake comes not from the cellar but from bread, processed meats, cheese, sauces, soups, ready meals and eating out. Salt reduction lowers blood pressure across populations, with the largest gains in those whose pressure is already raised, and it works through fluid volume and vascular effects that respond within weeks.

If a label declares sodium rather than salt, multiply by 2.5 to convert. So 0.4g sodium per 100g is 1g salt per 100g, which is on the high side. Where the salt content of a favourite product is stubbornly high, reformulating your own use helps: half the stock cube, rinse tinned pulses, and lean on lemon, vinegar, garlic, chilli, black pepper and herbs, which genuinely reduce perceived need for salt within a few weeks as taste receptors adapt.

For free sugars, the practical benchmarks are worth committing to memory. A 330ml can of standard cola contains around 35g, already above the adult daily maximum. A 150ml glass of orange juice contains around 13g of free sugars, which is why juice is capped at one portion a day. A standard chocolate bar sits around 25g. None of these is forbidden; the point is knowing what a 30g allowance actually buys, so the decision is deliberate rather than accidental.

Claims, health halos and marketing language.

Nutrition and health claims in the UK are regulated, with defined conditions attached to specific wordings. ‘Low fat’ requires no more than 3g per 100g. ‘Reduced sugar’ requires at least 30 per cent less than a comparable product, which can still leave a great deal of sugar. ‘Source of fibre’ requires 3g per 100g, ‘high fibre’ 6g. ‘No added sugar’ means none has been added but says nothing about naturally occurring sugars, and ‘unsweetened’ means no sweeteners either. ‘Light’ or ‘lite’ must state what has been reduced and by how much.

Unregulated language is where most of the persuasion happens. Natural, artisan, farmhouse, wholesome, clean, superfood, plant-based, gluten-free on foods that never contained gluten, and pictures of fields, grandmothers and hand-drawn typefaces all carry no nutritional meaning.

The predictable consequence is the health halo: people consistently underestimate the energy content of foods carrying virtuous cues and serve themselves more. Plant-based does not mean low in saturated fat, and organic does not mean low in sugar.

A workable routine takes seconds. Turn the pack over, glance at the per-100g column for saturates, sugars, salt and fibre, then read the first three ingredients.

Compare against the product beside it. Buy the better one. Do this consistently for the fifteen or twenty products that make up most of your weekly shop and the aggregate improvement is substantial.

If you are managing a diagnosed condition, a food allergy, coeliac disease or take medication with dietary interactions such as warfarin, check labels alongside advice from your GP, pharmacist or dietitian.