GENERAL POPULATION DIETARY GUIDELINES ARE NOT DESIGNED FOR PEOPLE WITH EXISTING DIABETES

Food-based dietary guidelines – also known simply as “Dietary Guidelines” – are intended to establish a basis for public food and nutrition, health and agricultural policies and nutrition education programmes to foster healthy eating habits amongst the general population. They provide advice on foods, food groups and dietary patterns to provide the required nutrients to the general public to promote overall health and to help prevent certain diet-related chronic diseases. To-date, more than 100 countries worldwide have developed Dietary Guidelines that are adapted to their nutrition situation, food availability, culinary cultures and eating habits (1).

Dietary Guidelines have been in existence since the early 1980’s with the most recent Australian version published in 2013, based on systematic literature reviews conducted mostly in 2009, capturing scientific evidence published between 2002 and 2009 (2).

In the 2009 reviews, selection criteria specifically excluded people with existing diabetes and other serious medical conditions. Therefore, despite popular misconceptions here in Australia (and elsewhere), the current Dietary Guidelines were not intended to be used by people with existing diabetes for diabetes management.

However, the 2009 reviews did include studies investigating dietary factors that affect the risk of diabetes. Based on the reviews, it was concluded that overweight and obesity, saturated fat, and sugar sweetened beverages, increase the risk of developing type 2 diabetes, but not sugars (insufficient evidence). On the other hand, consuming plenty of vegetables, legumes/beans, and fruit decrease the risk, possibly due to their fibre content. Similarly, grain (cereal) foods, mostly wholegrain and/or high cereal fibre varieties were also seen to reduce the risk. Finally, dairy foods (milk, cheese and yoghurt) were associated with reduced risk of type 2 diabetes (2).

All available carbohydrates by definition affect blood glucose. These include maltodextrins, starches and sugars. However, while there are specific Dietary Guidelines to “Limit intake of foods containing … added sugars…” there are no equivalent guidelines that specifically mention either the amount or quality of maltodextrins or starches. This is an unfortunate oversight from a diabetes risk-reduction perspective.

While the systematic reviews didn’t technically exclude studies that investigated glycemic index or glycemic load and the risk of developing diabetes, for some reason very few studies were identified and subsequently included in the 2013 Australian Dietary Guidelines on this important topic. This is despite the publication in 2008 of Glycemic Index, Glycemic Load and Chronic Disease Risk: a meta-analysis (3) in the American Journal of Clinical Nutrition. This important analysis determined that a high GI diet increased the risk of developing type 2 diabetes by 40% and coronary heart disease, a common complication of diabetes, by 25%.

Since 2009, a number of new systematic reviews and meta-analyses have investigated the role of glycemic index and load in the development of type 2 diabetes. Like the original 2008 analysis, Dr Geoffrey Livesey and colleagues looked at all of the prospective cohort studies published up until December 2018 that included 11.6 million person-years of new data and found that for every 10 unit increase in dietary glycemic index, the risk of developing type 2 diabetes increased by 27% and for every 80 g/day increase in dietary glycemic load, the risk of developing type 2 diabetes increased by 26%.

These new GI and GL data should be incorporated into the latest updates of Dietary Guidelines in Australia and other nations, and appropriate wording to decrease all refined carbohydrates (i.e., added maltodextrins, starches and sugars) will hopefully be included to help reduce the risk of developing type 2 diabetes.

Similarly, updates from Diabetes Canada and DiabetesUK should continue to recommend people with existing diabetes consume low GI carbohydrates instead of higher GI varieties, based on the compelling evidence that this strategy decreases HbA1c by an additional 0.31% points and fasting glucose by -0.36 mmol/L (4).

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