I concluded my presentation at the recent ILSI carbohydrate symposium by stating that sugar content is a poor measure of the nutritional quality of a carbohydrate-rich food. Here is a summary of the argument presented.
Discriminating between carbohydrate-rich foods
To illustrate the argument I used the model for discriminating between carbohydrate-rich foods developed by Professor Manny Noakes and myself. For more information on this model please refer to my previous post or the published paper.
In brief, the model is based on nutrient density and glycaemic index (GI). Nutrient density was chosen as it reflects the fundamental nutritional role of foods – the delivery of essential nutrients. And GI was chosen because it relates to the physiological effect of the carbohydrate itself. When carbohydrate-rich foods are run through the model they end up in one of four carbohydrate quality quadrants.
Dairy products – sweetened and unsweetened
Here is what happens when milks and yoghurts are run through the model.
All these products fall into the highest quality quadrant i.e. they are all nutrient dense foods and they all have low GIs. In Dr Alan Barclay’s presentation at ILSI he stated that nutrition dilution (not disease prevention) was the major nutritional negative associated with high sugar consumption and the model demonstrates this effect. Note the positions of reduced-fat milk and flavoured milk, which is essentially reduced-fat milk plus sugar. The flavoured milk is displaced to the left indicating that it has lower nutrient density – fewer nutrients for the same calories. This is the nutrient dilution effect of sugar. The same effect is apparent with natural low-fat yoghurt and sweetened low-fat yoghurt. So sugar is bad, right?
The other thing to note is that the sweetened dairy foods still fall in the highest quality quadrant – they are all nutrient-rich and all have low GIs, irrespective of their sugar content. Why then would nutritionists divide these foods into good and bad on the basis of their sugar content? Aren’t they all good? Including chocolate milk in a child’s diet does not have a nutrient diluting effect. It’s a nutrient-rich food – it has the opposite effect. A recent study showed that Australian children who drink plain or flavoured milk have higher micronutrient intakes but similar body mass index to those who do not drink milk. How can one argue that chocolate milk is an undesirable food?
Grain foods – sweetened and unsweetened
Here are the results when some refined cereal foods and breakfast cereals are run through the model.
Firstly, note that white rice, polenta, couscous, semolina and white pasta tend to cluster in the lowest quality quadrant – nutrient density is very low and GI varies from moderate to very high. Until recently these cereals were referred to as ‘core’ foods and their consumption was encouraged. I wonder why – look at white rice sitting deep in the lowest quality quadrant. Just because a food is a traditional food doesn’t necessarily mean it’s a healthy food. Although these grain foods contain no sugar their nutrient densities are so low that their inclusion in the diet has a nutrient dilution effect.
Compared to the unsweetened ‘core’ grain foods the nutrient densities of the breakfast cereals are consistently high, driven by their fortification. Some of these breakfast cereals have added sugar but in this context there is no nutrient dilution effect of sugar at all. In fact, including any of the breakfast cereals in a diet at the expense of any of the unsweetened ‘core’ cereals would enrich a diet with nutrients. Relying on the old starch-good/sugar-bad paradigm can produce perverse outcomes.
Sugar, energy density and GI
I recently surveyed Australian breakfast cereals to investigate whether their sugar content was associated with energy density or GI. Please take a look at the findings, which are now published. They show that sugar content of breakfast cereals has absolutely no association with either energy density or GI.
Think about this: In the context of breakfast cereals, sugar content has no association with nutrient density, energy density or GI. In other words, the sugar content is not related to any nutritional or physiological parameter that might actually affect health. This is why sugar content is a very poor measure of the nutritional quality of a carbohydrate-rich food.
Currently, health authorities are considering front-of-pack labelling systems to guide consumer choice. Using sugar, or added sugar, as a criterion for such a system would be a mistake. It would inevitably mislead. In developing front-of-pack food labelling and in nutrition education more generally two things are needed:
1. Meaningful measures of nutritional quality. If nutrient dilution is the concern with sugar, then why not make nutrient density a criterion?
2. Criteria that can be applied universally. If a criterion can’t be applied universally, then it is obviously flawed. If sugar is to be a criterion, it has to be applied to fruits. There is no place for subjectivity.
Nutrient density and GI are meaningful measures that can be applied to all carbohydrate-rich foods, which is why we used them in our model.