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Does sugar cause diabetes?

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The idea that eating sugar causes diabetes persists despite an increased understanding of the complex and multi-factorial aetiology of type 2 diabetes. We asked one of the nutrition community’s wise elders, Professor Paul Nestel for his words of wisdom on the topic.

Professor Paul Nestel AO MD FRACP FCSANZ FTSE
Professor Nestel is on the Senior Faculty at the Baker Heart and Diabetes Institute, Melbourne, and was previously Chief of CSIRO Division of Human Nutrition.

When did the notion that eating sugar causes diabetes come about?

On an academic level, possible associations between diabetes and the consumption of sugar have been around for decades. The fascination is cyclical having had a strong press in mid last century and resurfacing again in the last couple of decades. We certainly have better information now so that some conclusions can be made, although cautiously because associations do not establish causality.

What are the links between sugar and diabetes?

Obesity and type 2 diabetes (the usual form of diabetes) are closely linked. Whether sugar consumption plays an independent role in developing diabetes, or becoming fat, is less certain. From a dietary intake perspective excess energy intake from discretionary foods is far greater than energy intake from added sugar, including that from sugar sweetened beverages (SSBs).

Is there evidence that eating sugar increases the risk of type 2 diabetes?

The Harvard School of Public Health has published extensively from their huge database of tens of thousands of nurses and health professionals followed now for nearly 30 years. They have found significant associations-independent of body weight- between consumption of refined grains, SSBs (sugar sweetened beverages) and type 2 diabetes.  However, not all the evidence supports the US studies above. There have been robust studies showing no association between added sugar including SSBs and diabetes or cardiovascular disease.

Why are sugar sweetened beverages singled out?

Sugar in SSBs including fruit juices have been singled out largely because their consumption is easily remembered and counted. That is not to say that SSBs are not an important source of added sugar, or that the nutritional literature has not linked such beverages with type 2 diabetes. Excess SSB consumption has also been shown to lead to pre-diabetes, an earlier manifestation of diabetes in which blood fats and blood sugar become abnormally raised. Australian dietary surveys show alcohol, cakes, pastries, chocolates, confectionary and sweet biscuits account for much more energy- including energy from sugar - than SSBs.

What about Australia?

Sugar consumption in Australia has been declining. Consumption of SSBs is declining and the sugar content of SSBs has reduced yet obesity and diabetes show no signs of diminishing. Energy output is obviously not keeping pace with the consumption of discretionary foods that are meant to be eaten occasionally.

Which dietary components increase diabetes risk?

Higher dietary glucose load (from both sugars and refined carbohydrates), red meats and processed meats and fried foods, individually and especially collectively, raise the risk of diabetes and cardiovascular disease.

Are there any dietary components that reduce diabetes risk?

Losing weight and healthier eating patterns result in less diabetes. The Harvard group found higher consumption of coffee, wholegrains, fruits and nuts as well as fish is associated with lower risk of diabetes. Healthier dietary patterns such as the Mediterranean diet, the DASH diet (devised to lower high blood pressure) and similar, all have in common more plant food (vegetables, fruits, nuts, whole grains), fish and poultry, limited saturated fats and more unsaturated fats from healthier oils such as olive, canola and sunflower oils.

Is there anything else you’d like to add?

The news is not all bad. Healthier patterns of eating have been reported consistently and from very large populations. The food industry is adapting to provide healthier products, albeit somewhat slowly, to improve the food supply. Personally I do not support over the top suggestions such as a ‘sugar tax’; but there is a strong case for individual choices that are relatively simple, such as reducing SSBs and swapping discretionary foods for core foods.

NOTE: ‘Discretionary foods’ is the term used to describe foods high in saturated fats, sugars, salt and/or alcohol that can be included occasionally in small amounts, but are not a necessary part of the diet. Read more here

NEXT: Unnecessary avoidance of natural sugars  

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