Riddet Institute: Beyond the sugar debate
Beyond the sugar debate - Riddet scholars move focus to carbohydrates
Fundamental research, carried out by the Riddet Institute's Centre of Research Excellence (CoRE) members Professor Jim Mann and Dr Lisa Te Morenga, has given rise to new knowledge allowing food producers the opportunity to create scientifically-backed, high-value, nutritional products.
Their University of Otago team's work on sugar has helped create a world-wide conversation that will continue to have repercussions for food producers and the public for many years to come. Their work, which has been published in world leading medical and scientific journals including The Lancet, BMJ and American Journal of Clinical Nutrition, has been recognised by the World Health Organisation and helped to inform the development of WHO nutrition recommendations.
"There is now a public debate about sugar. Food companies and governments need to start making decisions based on the science in order to help reduce the epidemic of obesity and associated diseases," says Professor Mann.
Next year, through funding from the Riddet Institute CoRE, Dr Te Morenga plans to focus in on a different group of carbohydrates. How whole do whole grains need to be for the body to achieve maximum health benefits?
"Scientists are having to challenge a great deal of ill-informed public opinion," she says, "take for example Australian Master Chef Peter Evans' foray into dietary advice. He's advocating the paelo diet – a diet which is high in meat from which sugars are virtually eliminated and even grains, legumes and dairy food are radically reduced."
Dr Te Morenga says while our research shows that a high protein diet, which includes a moderate amount of minimally processed carbohydrate foods, may help overweight people to lose weight and reduce their risk of chronic diseases, these diets can be difficult to follow over the long-term because you can’t easily buy ready-to-eat high protein meals. We have also shown that diets high in dietary fibre from whole grains and legumes have important benefits such as controlling blood sugar and blood cholesterol levels. However, once again it can be hard to eat a whole grain rich diet because the whole grain foods available to consumers are either difficult to prepare or have been processed in ways which may minimise their benefits.
"Limited availability of appropriate food choices can be a problem for people wishing to follow the dietary recommendations. Many processed foods are easily accessible and strongly marketed. We all know the refrains, 'buy two for the price of one', 'upsize', 'you're worth it' - this marketing spin goes completely against the grain of dietary advice."
Dr Te Morenga and the Riddet Institute will investigate whether processing diminishes the known benefits of whole grains. They will also examine how diets rich in protein and whole grains influence the microbiota that live in our large intestine. "These bugs may have positive or harmful health effects but little is currently understood about how such foods affect long-term health. We will then be better able to refine dietary recommendations and provide guidance to the food industry about how to produce foods that provide the greatest health benefits for consumers."
"Our most immediate interest relates to the definition of whole grains: do finely ground grains have the same benefits as whole grain foods that retain more of the grain structure? The current definition allows grainy foods to be described as whole grain even if finely ground. This makes them easier to incorporate into processed foods but we need to find out whether this is appropriate."
Meanwhile, sugar has recaptured the public interest. Professor Mann says it is now well recognised that too much saturated fat increases the risk of heart disease and that diets high in fat can lead to weight gain. Food companies responded by producing a wide range of fat reduced products to meet an increasing consumer demand. Unfortunately, fat is often replaced with sugar with the result that the public is now consuming very high amounts of sugar. Professor Mann began investigating the health effects of sugars 40 years ago as part of his PhD research but he says many questions still remain.
Professor Mann’s team has demonstrated that high intakes of sugar can contribute to obesity and associated illnesses; diabetes; heart disease; and, cancer. “We have shown that diets higher in added sugars results in greater body weight gain than diets lower in added sugars”. However, he says the team has also shown that there is nothing special about sugar calories, as is sometimes claimed. It seems that people gain weight on high sugars diets because they consume more calories than they need. One theory suggests that our bodies are less sensitive to recognising when we have consumed enough calories when they are consumed in liquid form. And, these days sugary drinks are a major contributor to sugar intakes. It’s also easy to pack a lot of sugar into a small volume of food so people may not realise just how many calories they are consuming even when eating small quantities of food. It’s a similar story with fat."
The team also investigated whether there are specific effects of sugar on blood pressure and blood fats. “We found that higher sugars intakes has a small but meaningful effect in comparison with lower intakes.”
Professor Mann and Dr Te Morenga’s sugar research has contributed to the development of World Health Organisation recommendations on sugar intakes and has contributed to the public debate on the potential harms of too much sugar.
In 2015 they will continue to investigate the role of sugar in human health; aiming to better understand what is needed to help consumers to reduce their sugar intake while not compromising other aspects of a healthy diet. They will also continue to study the health effects of sugar from different sources. For example is sugar in fruit drinks the same as in whole fruit? This research will hopefully be published in 2015.
"Alongside other scientists from around the world, we've influenced international and European nutritional guidelines for people with diabetes. Our work in the field of diabetes has been particularly widely recognised." he says.
"New Zealand scientists are world leaders in the field of nutrition. Much of the work has been made possible as a result of funding from the NZ Government to the Riddet Institute Centre of Research Excellence," says Dr Mann. "The Riddet Institute provides us with the freedom to explore nutrition, to research and offer scientific backed advice to the public. As a result, the Riddet Institute is having a positive effect on food nutrition and New Zealand's scientific reputation."