An average adult within the healthy weight range has a total energy intake of about 8700 kilojoules a day.
For this person, 10 per cent of energy intake equates to approximately 50g (around 12 teaspoons) of sugar a day, while 5 per cent is about 25g of sugar.
The suggested limits apply to sugars added to food by manufacturers, cooks or the consumer of the food, as well as sugars naturally present in honey, syrups, fruit juices and fruit concentrates.
The problem is that sugars in these latter (and many other) foods are "hidden" in the sense that people don't always account for them when considering their sugar intake. And there's increasing concern that these kinds of sugar sources may displace more nutritious foods in the diet, thereby increasing the risk of ill health through conditions such as diabetes and heart disease.
Sugars also play a major role in the development of dental caries or cavities (tooth decay), which continues to cause pain and loss of function in many people.
There are masses of hidden sugars in other common foods too. Most of the processed foods available in supermarkets today, for instance, contain added sugar - often in surprising quantities. This includes even those that don't taste particularly sweet.
Tomato sauce, for instance, is considered a savoury food, but one tablespoon contains approximately 4g of sugar.
High-sugar foods and drinks that provide little nutritional value are the ones to watch out for - these are mostly discretionary or junk foods (also known as "extras" or "sometimes foods"), such as sugary drinks, lollies, chocolate, biscuits and cakes.
The Australian Dietary Guidelines point out that discretionary foods are not a necessary part of the diet - and there are good reasons why.
It's clear that adding just one serve of some of these foods (and others like them not described above) to an otherwise sugar-free diet means exceeding the WHO draft suggested limit of 5 per cent. In some cases, it would even mean approaching the recommended upper limit of 10 per cent! What's more, these serving sizes may not accurately reflect what most people eat. People don't tend to use standard serving sizes and may eat even more than the quantity of sugar shown above.
Sugar is also commonly added to grain foods, especially breakfast cereals and bread. A standard 30g serve (two-thirds of a cup) of typical sugar-sweetened breakfast cereal, for instance, contains approximately 8g of sugar. And a 40g slice of commercial white bread contains approximately 1.5g.
But unlike most discretionary foods, bread and breakfast cereal usually also provide valuable nutrients. Still, because they provide more essential nutrients, it's better to choose mostly wholegrain or high-fibre (or both) cereals and bread, without added sugar.
Sugar has a place in a healthy diet, especially for encouraging consumption of nutritious foods by fussy eaters. Adding a teaspoon of honey to rolled oats to make breakfast more palatable, for instance, is better than not eating oats at all. Neither the Australian Dietary Guidelines nor the draft WHO guidelines recommend avoiding sugar entirely.
Although it may be difficult to meet such guidelines, they help raise awareness about the importance of a balanced diet, including the need to limit sugar intake. Don't beat yourself up for exceeding the daily limit occasionally, just remember that it's definitely worth the struggle to try to match the recommendations.
Kate Flinders is a defence scientist (nutrition) at Australia's Defence Science and Technology Organisation.
