DFN Board member Dr Luke Wilson separates the myths from the facts about diet and diabetes for the Australasian Society of Lifestyle Medicine blog.
The relationship between diabetes and nutrition is often oversimplified and equated with an excess of ‘sugar’ or glucose in the diet, by clinicians and laypeople alike. Unfortunately, this widely held belief and the resulting dietary choices are contributing to the current epidemic of type 2 diabetes and poor outcomes for patients with diabetes.
Certainly, both types of diabetes are defined by an excess of glucose in the blood. However, the amount of glucose in our blood depends mostly on our body’s ability to use the glucose we consume, with availability and sensitivity to insulin being the critical factor. Excitingly, by revising our own and our patients’ nutritional approach to diabetes, we can ‘reverse’ most cases of type 2 diabetes, and help those with type 1 diabetes dramatically reduce their insulin use and risk of complications and chronic disease.
It is clear that the Western diet plays a key role in our current epidemic of type 2 diabetes.
This diet is characterised by high fat consumption, high protein consumption (both largely from animal sources), and a moderate intake of carbohydrate (largely from refined sources, especially sugar and flour). For example, the average diet in Australia and New Zealand is approximately 32% energy from fat, 17% protein, and 46% carbohydrate. As we see populations that have traditionally consumed a diet considerably higher in carbohydrate, but lower in fat and protein move towards the Western dietary pattern, a dramatic corresponding increase in type 2 diabetes occurs.
In China in 1980 less than 1% of the population had type 2 diabetes. At this stage, the Chinese diet had just begun to shift towards Westernisation. In 1970 for example, the Chinese diet was approximately 8% energy from fat, 10% protein, and 83% carbohydrate. By 2011, this had ‘Westernised’ to 32% fat, 13% protein, and 54% carbohydrate. It has been estimated that 11.6% of the Chinese population now have diabetes and 50.1% have prediabetes.
Across the Pacific in the United States, the Native American Pima people of Arizona are thought to have perhaps the highest prevalence of type 2 diabetes in the world: about 50% of all Pima over the age of 35 are affected. Their diet is similar in both total energy and macronutrient composition to that of the general population in the US, with approximately 35% energy from fat, 15% protein, and 47% carbohydrate. Intriguingly, the Pima of Mexico, who are very closely related genetically, have a substantially lower prevalence of type 2 diabetes at 13.4%. Their diet is more traditional and ‘…remarkable for the low percentage of calories derived from fat…’ at approximately 26% fat, 11% protein, and 62% carbohydrate.
While Westernisation of diet is also accompanied by increased food availability and substantially reduced physical activity, increases in rates of type 2 diabetes trend with increased fat intake, not an increased carbohydrate intake.
While Westernisation of diet is also accompanied by increased food availability and substantially reduced physical activity, increases in rates of type 2 diabetes trend with increased fat intake, not an increased carbohydrate intake. Even refined sugar, often blamed for the diabetes epidemic, seems to have little role in its aetiology besides as a source of additional energy. Furthermore, the idea that refined sugar is hazardous for glycemic control in people with type 2 diabetes is not supported by research. In one study, glucose control actually improved on a higher sugar diet, where participants were supplemented with 60g of fructose per day in place of complex carbohydrates, despite no changes in body weight10! Of course, there are plenty of other reasons why we should all minimise or avoid refined sugar, but at the very least from the above examples we can conclude it is possible to eat a diet that is very high in carbohydrate, perhaps even refined carbohydrate, compared to current diets in Australia and New Zealand without developing type 2 diabetes. If the high fat intake of the Western diet is instead implicated, why might this be the case?
It is now well known that body mass index and type 2 diabetes are closely related.
The risk essentially increases linearly as BMI increases, and weight gain after age 18 is a major determinant of risk. While it is often assumed that refined sugar and carbohydrate are the major contributors to excess energy intake in Western society, again this idea is not supported by research. A recent UK study found that compared to those with normal BMI, obese participants had a 14.6%, 13.8%, 9.5% and 4.7% higher intake from fat, protein, starch and sugar, respectively. In fact, it was concluded that because the proportion of fat in the diet, rather than sugar, was higher among overweight and obese individuals, focusing public health messages on sugar may mislead on the need to reduce fat and overall energy consumption.
Unsurprisingly then, type 2 diabetes can be effectively treated by weight loss.
A recent and exciting finding was that intensive weight management in a primary care setting resulted in remission of diabetes in 46% of participants. Remission varied with the weight loss achieved, increasing from 7% of participants who maintained 0-5kg of weight loss to 86% of those who lost 15kg or more. Unfortunately, the intervention was indeed ‘intensive’, replacing all food with a mere 825-853kcal a day of a high carbohydrate, low fat formula for between 3-5 months...
Read the full referenced article at lifestylemedicine.org.au/content/type-2-diabetes-and-nutrition.
More about the author
Dr Luke Wilson is a Doctors For Nutrition Board member and 'Ambassadoc' for New Zealand.
Read his full bio here.