How to Read Food Labels: Serving Sizes, Sugars, and Ingredients

A food label is built to be read quickly in a supermarket aisle, but the numbers only make sense if you know what they refer to. The same product can look low in sugar on one label and high on another, simply because one reports per serving and the other per 100 grams. Once you know what to check first, a label takes about 20 seconds to read.

This guide is for anyone who wants to compare packaged foods fairly, whatever country they shop in. You will learn the main label formats, how to use serving sizes and per-100 g figures, how to spot added sugars, what ingredient order tells you and how to flag allergens. A worked example shows how a "healthy-looking" product can change when you compare it fairly.

The three main label styles

Regulations vary by country, so check what applies where you shop. These are the three styles you are most likely to see.

Other countries use variations: some have warning labels for high sugar, salt or fat, others use star ratings or simple front-of-pack symbols. The ideas below carry across all of them.

Serving size versus per 100 g

The European Commission states that the mandatory nutrition declaration in the EU must be expressed per 100 g or per 100 ml, and may also be given per portion. The NHS in the UK warns that the manufacturer's idea of a portion may not be yours.

This is where most mistakes happen. A small serving size makes numbers look smaller. The US Food and Drug Administration (FDA) reminds shoppers that all calories and nutrients on a Nutrition Facts label refer to one serving, so eating two servings doubles them. It also says the serving size is not a recommendation of how much to eat.

Use this rule:

1. Check the serving size and the number of servings in the pack.
2. Ask how much you will actually eat, and multiply.
3. Compare products using per 100 g where available. If a label only gives per serving, convert it yourself (see the worked example below).

Traffic lights and % Daily Value

Traffic-light labels, used in the UK on a voluntary basis, show red for high, amber for medium and green for low. The NHS lists per-100 g thresholds for food:

Drinks use different thresholds. Amber is not bad. It means eat in moderation, and it is common for many ordinary foods.

In the US, the Nutrition Facts panel uses percent daily value. The FDA explains that 5 percent DV or less per serving is low, and 20 percent or more is high. These percentages are based on a 2,000-calorie diet, which is a general guide rather than a personal target. Choose products with lower %DV for saturated fat, sodium and added sugars, and higher %DV for fiber, calcium, iron and potassium.

Salt and sodium are not the same. Labels in some countries list sodium, others list salt. The NHS page gives 1.5 g of salt as equal to 0.6 g of sodium, so salt is about 2.5 times the sodium figure.

Total sugars versus added sugars

Total sugars include sugars that occur naturally in milk and fruit as well as sugars added during processing. The FDA explains that added sugars include sugars put into a food during processing, sweeteners, syrups, honey, and sugars from concentrated fruit or vegetable juices.

Only some regions show an added-sugars line. In the US, it appears under total sugars and has a %DV. In the EU and UK, labels list total sugars, so check the ingredients to see whether sugar comes from fruit or milk or has been added.

Sugar goes by many names. Look in the ingredients for:

• Sucrose, glucose, fructose, dextrose, maltose
• Syrups (glucose syrup, corn syrup, golden syrup, maple syrup, rice syrup)
• Honey, agave, molasses
• Fruit juice concentrate

A product with three different sugars listed separately may have more sugar overall than the order suggests, because each one appears lower in the list.

Reading the ingredient list

In most regions, ingredients must be listed in descending order by weight at the time of manufacture. The first three ingredients usually make up most of the product. If sugar or a syrup is near the top, the food is sweet by design. If the first ingredient of a "whole grain" bread is refined flour, the claim may be more about marketing than substance.

Other points:

• Shorter is not always better. A long list can include vitamins, spices or preservatives that are harmless.
• Look for specifics. "Vegetable oil" tells you less than "sunflower oil".
• Check percentages. Some labels state the percentage of key ingredients, such as the fruit in a jam or the meat in a sausage.
• Be careful with front-of-pack claims. "Natural," "light," "multigrain" and "made with real fruit" often have little regulation. The FDA suggests comparing %DVs instead of memorizing claims such as "light" or "reduced".

Allergens

If you or someone you cook for has a food allergy, read the ingredients every time, even for products you buy often, because manufacturers change recipes. Many regions require major allergens to be highlighted in the ingredients list, for example in bold, or declared in a separate "contains" statement. The list of required allergens differs by country. Warnings such as "may contain traces of" are often voluntary and unregulated in some places, so contact the manufacturer if you need certainty.

Worked example: comparing two cereals

Say you are comparing two hypothetical granolas. Neither product is real.

• Granola A: serving size 30 g, with 7.5 g of sugars per serving.
• Granola B: serving size 50 g, with 9 g of sugars per serving.

On the front of the pack, A looks better, with less sugar per serving. Convert both to per 100 g.

1. Granola A: 7.5 g divided by 30 g, times 100, equals 25 g per 100 g.
2. Granola B: 9 g divided by 50 g, times 100, equals 18 g per 100 g.

Granola B is lower in sugars per 100 g, even though its serving contains more. Using the NHS thresholds, A is above 22.5 g and would be red, and B is amber. If you eat a 50 g bowl of A, you get 12.5 g of sugars, more than B.

The point is not that one is good and the other bad. It is that the comparison only works on an equal basis.

Common mistakes

• Comparing per-serving figures between products with different serving sizes.
• Assuming the pack is one serving. Check how many servings it holds.
• Trusting front-of-pack claims instead of the nutrition table and ingredients.
• Ignoring fiber and protein. A food with moderate sugar and plenty of fiber can be a better choice than one with less sugar and none.
• Treating all sugars the same. Whole fruit and milk differ from added sugars in drinks, though labels do not always make this clear.
• Fixating on calories alone. Look at the whole panel, including salt and saturated fat.

Frequently asked questions

Are traffic-light labels required?

In the UK they are a voluntary scheme, so you will not see them on every product. Other countries use different systems, so learn the one where you live.

What does "no added sugar" mean?

It means no sugars were added during processing, but the food may still contain natural sugars, for example from fruit. Check total sugars in the nutrition table.

Which matters more, the nutrition table or the ingredient list?

Use both. The table tells you how much, and the list tells you what and in what order. Together they answer most questions in the aisle. This is also useful when you plan meals, as in meal prep for beginners.

What about drinks?

Use per 100 ml to compare, then multiply by the amount you drink. Many bottles contain more than one serving. See how much water you really need for ways to meet your fluid needs without relying on sweetened drinks.

Next steps

1. Pick three products you buy often and convert their sugar and salt to per 100 g.
2. Check the first three ingredients on each.
3. Use the thresholds in this guide as a rough guide, and compare alternatives in the same category.
4. If you have allergies, create a habit of reading the ingredients list every time you shop.