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Not all sugars are created equal

Sugar-sweetened beverages don't necessarily lead to type-2 diabetes

Andrew
Wheatley

Thursday, October 11, 2018

Tim Lobstein, director of policy, World Obesity Federation, London, UK, in September 2014, reported, inter alia: The consumption of sugar-sweetened beverages, has been suggested as a contributory factor to the rising levels of childhood obesity in many countries worldwide. Recent systematic reviews of the literature confirm the link between increased intake of free sugars, particularly in the form of sugar-sweetened beverages and unhealthy weight gain in both children and adults; while reducing consumption of sugar-sweetened beverages has been shown to reduce weight gain in children, particularly in those who are already overweight.

This report focuses on sugary drinks and obesity.

The World Health Organization (WHO) guidelines of 2015 states: “We have solid evidence that keeping intake of free sugars to less than 10 per cent of total energy intake reduces the risk of overweight, obesity and tooth decay. Making policy changes to support this will be key if countries are to live up to their commitments to reduce the burden of non-communicable diseases.”

The WHO guideline, however, does not refer to the sugars in fresh fruit and vegetables and sugars naturally present in milk, because there is no reported evidence of adverse effects of consuming these sugars. The explanation herein is that the sugars presented to the body in these foods are mixed with soluble fibre which slows the sugar release into the blood; hence, the body is better able to use this sugar without it achieving high levels, which would result in fat deposits.

The age-old question as to the role of sugar in developing obesity is still not settled, and the issues being grappled with as recently as over the past decade are: Do sugar and sugar-sweetened beverages predispose one to excessive weight gain?

What is the role of sugar as a component of energy-dense food in the aetiology of obesity?

Does sugar have a special role in people with high blood pressure, high blood sugar, high blood fats and cholesterol, overweight and an increased tendency to heart and blood vessel disease, and even sudden death? (NB: This latter group of conditions is referred to as the metabolic syndrome in scholarly writings.)

Various studies (Malik & Hu 2012; Morenga, Mallard & Mann 2013; Imamura et al 2015) all reviewed multiple studies and, whilst supporting an association between obesity and type 2 diabetes (T2D), the results have not been able to demonstrate a causal relation. What seems to be emerging is the effect of fructose (fruit sugar), which is not influenced by insulin. It is taken up directly by the liver and converted into glucose storage, glycogen, and fat. This fat leads to deposits in the liver and other abdominal organs, resulting in resistance to insulin which in turn can lead to T2D.

Thus, the strong evidence supports sugar linked to obesity and that's where the evidence stops. Over more than a century the question as to whether sugars cause diabetes has been studied and these studies extensively reviewed… And there is no evidence that sugar intake causes diabetes mellitus. We believe that excessive sugar intake will aggravate diabetes by way of increasing the blood levels, but it does not cause it. In fact, the American Diabetes Association and Diabetes UK have labelled the notion that sugars and sugary drinks cause T2D a “myth”. Hence, the current debate is apparently confusing the public discourse.

The Ministry of Health wants to encourage reduction in sugar intake in its quest to reduce obesity, and that is in keeping with the WHO's recommendation. But the public discourse is whether sugar causes diabetes and much heat is being generated with little or no light. The assertion of our local guru, Professor Errol Morrison, that there is no known causal relationship between sugar intake and diabetes is supported by worldwide studies and leading opinions, and I leave it at that as the scientific truth shall prevail.

I want to return, however, to the matter of sugar intake and obesity and to highlight the delivery of sugary foods and drinks of sugar into the body. The best way to ascertain the real propensity of a drink or food to increase blood sugar levels is by way of measuring its glycemic index (GI). This is a measure of sugar released compared to the reference of 100 grams of glucose.

My studies at The University of the West Indies (UWI) Department of Basic Sciences on Caribbean foods have shown such values and pointed to recommendations for one food type as opposed to another. The GI of foods are not solely dependent on the sugar content. In fact, one must take into consideration the very form in which the sugar is present. Processing method, fat and protein content, fibre and acid content are some of the factors that influences the GI of a food. You might be surprised, therefore, to learn that yams release sugar more readily than sweet potatoes, and even alarmed to know that white rice has a higher GI than the common table sugar.

It has become fashionable in recent years to blame sugar for many health problems. However, per capita sugar consumption has been falling in the United States since 1999, when bottled water and sugar-free beverages began to edge sodas off the shelf. At the same time, consumption of cheese and oily foods has steadily increased, as has diabetes prevalence. This suggests that something other than sugar is driving the diabetes epidemic.

Research has shown that the transition from traditional carbohydrate-rich (eg rice-based) diets in Asia to lower-carbohydrate Westernised eating habits emphasising meats, dairy products, and fried foods has been accompanied by a major increase in diabetes prevalence.

The roots of type 2 diabetes remain in insulin resistance and pancreatic failure.

The move to reduce sugar content in sugar-sweetened beverages is a positive move to reduce obesity, but it must not be construed to imply that it prevents T2D. In fact, not all sugars are created equal.

 

Dr Andrew O Wheatley is a Member of Parliament and research scientist/senior lecturer in basic medicine and biotechnology. He has done extensive work on diabetes management and the glycemic index. The holder of two international and two local patents and has published extensively in peer-reviewed international journals.