Sugar in focus

How much sugar is OK to include in our diet?
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  • Updated:13 Sep 2005

02.Effects of sugar

Tooth decay

Sugar is one of several things that can contribute to tooth decay (dental caries). Although sugar (sucrose) is at the top of the list for its decay potential, it’s by no means the only suspect. How you eat it and how well you care for your teeth are also important parts of the equation.

All sugars can be used as food by bacteria in the plaque on your teeth. The bacteria produce acids that can eat into tooth enamel, so all types of sugar can be a problem under the right conditions, as can starches and starchy foods. How much of a problem depends on how often you eat them through the day and how long they stay in your mouth.

Frequent snacking on sugary or starchy foods, and in particular ones that hang around in your mouth, like sticky, clingy biscuits, cakes and sweets, or foods you sip or suck for some time, can easily result in problems your dentist won’t be happy about. Eating these foods as part of a meal is better than having them between meals.

Good oral hygiene is also a critical factor — regular teeth cleaning with a fluoride toothpaste, flossing and check-ups are essential to healthy teeth, no matter how much sugar you do or don’t eat.


The physiology of getting fat is pretty straightforward. Despite what fad diets might have you believe, if you eat more energy (kilojoules/calories) than you use, the extra is stored as fat and you’ll become fatter over time. We all know this, we’d just like a simple eating ‘trick’ or easy ‘diet’ to make it otherwise. And it doesn’t matter where those extra kilojoules come from — fat, protein or carbohydrates (including sugar) — eat more than you need and you’ll get fatter.

But a healthy diet isn’t just eating the right amount of energy for your needs, it’s also about getting all the vitamins, minerals, fibre and phytochemicals you need to be healthy. The one thing that refined sugar does is to add energy (kilojoules/calories) without adding any other nutrition.

This can make it difficult for heavy consumers of sugar, who may eat sugary products instead of more nutritious foods and end up missing out on what they need for a healthy diet. Many sugary foods, such as pastries, biscuits, cakes, confectionery and soft drinks, are low in nutrition but high in kilojoules.

Of course, a little sugar can also make more nutritious foods more likely to be eaten: porridge with brown sugar or wholemeal toast with jam, for example. That’s why, on balance, we’re advised to eat only a moderate amount of sugars and foods containing added sugars. But just how much sugar is that?

Blood sugar and GI

Eating sugary foods used to be blamed for sending people’s blood sugar levels soaring and then plunging — surges which some nutritionists think could have long-term effects on health.

But while some foods can send blood sugar levels bouncing, it seems the answer to which foods do this isn’t as simple as just those with the most sugar.

The glycaemic index (GI) of foods is a way of measuring how they affect levels of sugar in the blood, giving each food a comparative score out of 100. It compares the effect of eating an amount of each food that contains 50 grams of carbohydrate with eating the same amount of pure glucose (GI = 100).

Foods with a low GI (55 or less) make blood glucose levels rise and fall more gently, while high-GI foods (70 or more) are broken down more quickly and cause blood sugars to surge and crash. Perhaps surprisingly, table sugar scores a moderate 61.

Syndrome X

It sounds like a pilot for a sci-fi series, but in fact it’s a name coined to describe a cluster of abnormalities associated with insulin resistance, high blood pressure, obesity (centred around the stomach), low HDL-cholesterol (that’s the good kind) and high blood triglycerides — all of which increase the risk of diabetes and heart disease.

A link has been suggested between syndrome X and large quantities of fructose — a type of sugar used much more extensively in processed foods in the US than here, but which also makes up one half of a molecule of ordinary sugar (sucrose). The science is far from clear. There are animal studies that support the idea, but a very limited number of human studies. Some experts say there’s not enough fructose in Australian diets to have any noticeable effect, but it’s early days and more research is needed. There’s no suggestion that eating fruit (which provides fructose in association with dietary fibre) is a risk.



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