By Bill Shrapnel
Professor Jennie Brand-Miller from Sydney University refers to carbohydrate as the ‘default nutrient’ – nutritionists assumed it was beneficial for health because they were concerned about everything else. Saturated fat raised LDL-cholesterol; unsaturated fats were still fats and therefore were treated with suspicion; protein was assumed to be a constant; and alcohol was out of the question.

As nutritionists also recommended lower intakes of sugar the default nutrient was actually starch. Starchy foods were healthy foods and the public was encouraged to eat plenty of them.

Recent scientific findings demand that nutritionists reconsider their advice about carbohydrate-rich foods.

Rather than carbohydrate being the ideal substitute for saturated fat in the diet it has now been confirmed that these macronutrients confer the same risk for coronary heart disease (1). This has had two major consequences.

Firstly, it is now recommended that saturated fat be replaced by unsaturated fats, especially polyunsaturated fats, as the evidence for benefit from this exchange is consistent and strong. It follows that the recommended total fat intake is now moderate, not low.

The second consequence is an increased focus on the poorly defined concept of carbohydrate quality. No-one imagines that all carbohydrate-rich foods are equally beneficial or harmful in relation to heart disease but which parameters should we assess them on? Western diets include all sorts of carbohydrate-rich foods – some high in starch, others high in sugars, some high or low in fibre, some are nutrient-rich while others are nutrient-poor, some are high or low in GI, and some are wholegrain. The potential combinations are endless.

Carbohydrate conundrums

Historically, nutritionists have judged carbohydrate-rich foods on just a few criteria – foods with appreciable added sugar were perceived negatively and foods rich in fibre were seen as healthy choices. More recently whole foods, such as wholegrains, have been encouraged though there is a philosophical dimension to this.

It assumes whole foods are nutrient-rich and lack adverse consequences but neither turns out to be the case. Unfortunately, carbohydrate conundrums abound:

• Some wholegrain foods, such as brown rice, are nutrient-poor
• Many foods rich in starch, the default nutrient, have high GIs
• Wholemeal bread has a high GI
• White bread is more nutrient-rich than some wholegrain foods
• White rice is nutrient-poor and has a high GI
• Flavoured yoghurts and milks have added sugar but are still nutrient-rich and have low GIs
• Breakfast cereals with high or low sugar content have similar energy densities, nutrient densities and GIs (2). Sugar versus starch

Relatively few carbohydrate-rich foods are unequivocally healthy choices – legumes, a few vegetables, a few breads, many fruits and some dairy products.

At the other end of the spectrum there are some foods that tick none of the boxes, including the usual suspects such as biscuits, cakes, pastries, confectionery and soft drinks. However, some starchy foods previously considered healthy choices, such as white rice and semolina, are nutrient-poor, with little fibre and high GIs – they really belong with the biscuits and cakes.

Assessed using objective criteria, the best and the worst choices among carbohydrate-rich foods have one thing in common – both contain varying amounts of sugars and starch. Some high sugar foods fall in the most desirable category while some starchy foods fall in the least desirable category. It follows that whether carbohydrate-rich foods are high in sugar or starch is irrelevant when assessing the healthiness of these foods.

The starch-good, sugar-bad paradigm is part of dietetic folklore and gets passed on from one generation of nutritionists to the next, but it’s not a scientifically valid distinction. Recommendations about carbohydrate-rich foods need to be objectively based, universally applied and meaningful.

REFERENCES

1. Jakobsen MU, O'Reilly EJ, Heitmann BL, et al. Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. Am J Clin Nutr 2009;89:1425-32.
2. Shrapnel B. Amount of sugar in Australian breakfast cereals is not associated with energy density or glycaemic index: Results of a systematic survey. Nutr Diet 2013;70:236-240.

Bill Shrapnel is one of Australia’s most experienced dietitians. He has a strong interest in carbohydrates and has developed a model for assessing the nutritional quality of carbohydrate-rich foods. He is an independent advisor to the SRAS.