By AP

Walk down any supermarket aisle in London and you will see packets shouting "no added sugar", "keto friendly" or "low carb" on the front. Turn the packet over, however, and the nutrition table and ingredients list often tell a very different story.

You do not need a nutrition degree to know what you are buying. Once you know two simple rules for UK food labels, you can turn over any packet in your cupboard or the supermarket aisle and read it in about 30 seconds.

1. How to work out net carbs on a UK food label

If you follow a low-carb or keto diet, or you simply keep an eye on how food affects your energy and blood sugar, you have probably come across the phrase net carbs. It means the carbohydrates your body actually digests and absorbs as glucose.

Here is the rule for UK and EU nutrition labels:

Net carbs on a UK label = Total Carbohydrate minus Polyols

For example, if a nutrition table says Carbohydrate 20 g, and underneath says of which polyols 12 g, you are looking at roughly 8 g of carbohydrates that count.

Do not subtract fibre on a UK label

This is one of the most common mistakes people make when reading American nutrition advice online. On US labels, dietary fibre is bundled inside the total carbohydrate number, so Americans have to subtract fibre to find their net carbs.

On UK and EU food labels, fibre gets its own separate line in the nutrition table. It has already been taken out of the carbohydrate figure for you. If you subtract fibre again on a UK packet, you will undercount your carbohydrates - sometimes to a negative number.

The big catch: not all polyols are equal

When a label lists polyols (also called sugar alcohols), the next step is to glance at the ingredients list to see which polyol the maker actually used. Two products with the exact same polyol numbers on the back can behave very differently in your body:

• Non-GMO erythritol (from corn): Erythritol passes through the body largely unabsorbed, has a glycaemic index of zero, and counts as zero calories under UK food labelling rules. At Yummzy, we sweeten our bakes with non-GMO erythritol from corn alongside organic stevia.
• Maltitol: Maltitol is cheap and behaves like sugar in factory machinery, so it is widely used in supermarket "no added sugar" chocolate bars and sweets. However, maltitol is partly absorbed by the body, has a glycaemic index around 35 to 52 (for comparison, table sugar is around 65), and can still raise blood sugar as well as cause digestive discomfort.

So when you subtract polyols on a UK label, always check the ingredients list: if the sweetener is erythritol, you can subtract it with confidence; if it is maltitol, treat a significant portion of it as a carbohydrate that still counts.

2. Sugar has many names (and the order matters)

A product can claim "no refined sugar" on the front while still packing several forms of sugar into the recipe. You do not need to memorise fifty different ingredient names. Instead, look for two simple patterns:

1. Words ending in "-ose": Sucrose, glucose, dextrose, fructose and maltose are all sugars.
2. Anything called a syrup, nectar or concentrated juice: Rice syrup, corn syrup, maple syrup, agave syrup, date syrup, honey and coconut blossom nectar all act as sugar in the body, regardless of how natural they sound on the front of the box.

Just as important is where they appear. By law, UK food labels list ingredients in descending order by weight. Whatever comes first makes up the biggest share of the product.

Another trick to watch for is sugar splitting. A manufacturer might use a little brown rice syrup, a little coconut sugar, a little dextrose and a little concentrated fruit juice so that no single sugar sits right at the top of the list - even though, combined, sugar is the main ingredient.

Why we put full numbers on everything we bake

At our cafe at 18-19 Cabot Square in Canary Wharf, we believe you should never have to guess what is in your food. We do not use cane sugar, honey, maple syrup, agave, dates or maltitol. Instead, we bake with almond flour, coconut flour, non-GMO erythritol from corn and organic stevia, so every single item on our counter is vegan, gluten-free, refined-sugar-free, keto and low carb at the same time.

That is why you can check the ingredients and approximate macros per slice right on our website before you visit or order - whether you are choosing a Triple Choco Cake or Gluten-Free Birthday Cake in London for a celebration, ordering Office Catering in Canary Wharf for your team, or popping into Cabot Square for a Gluten-Free Breakfast in Canary Wharf with a fresh Focanini sandwich or a slice of our Earl Grey Loaf.

Try the 30-second cupboard test

Pick one item from your kitchen cupboard or desk drawer today - especially something marketed as "healthy", "protein" or "no added sugar" - and turn it over:

1. Check Carbohydrate and polyols (and see which polyol is in the ingredients).
2. Scan the first five ingredients for "-ose" words and syrups.

If you enjoy quick, practical tips like this - plus first dibs on our monthly Latte Art Workshops, Thursday Salsa and Chess Coffee Mornings at Yummzy Events - sign up to our monthly Yumm A Month newsletter at the bottom of yummzy.co.uk.