Research guides better health

Sugar, carbohydrate, sodium: nutrition research at Otago is influencing and informing World Health Organization guidelines.

There has been much international debate about sugar and its impact on obesity and diabetes. However, this controversy is now being resolved with World Health Organization (WHO) guidelines on sugar that have been developed with vital input from University of Otago nutritionists.

Professor Jim Mann (Department of Human Nutrition) is one of an international team of researchers and clinicians who developed the WHO guidelines and produced a set of rather stark findings.

“The key message is that sugar is a major determinant of excess bodyweight and of dental caries worldwide. That excess bodyweight – or obesity – is one of the major causes of non-communicable disease and the importance of dental caries should not be underestimated.”

“With six per cent of health budgets around the world going towards treating dental caries, sugar should be restricted to an extent that has never been recommended before. No individual should have more than five per cent of their total calories coming from sugar – and that is actually very little sugar,” he says.

“What is interesting is that a lot of things in nutrition have been controversial, including sugar, but sugar has almost moved out of the realms of controversy now.”

However, new controversies are likely, with further WHO nutritional guidelines on the way. Mann's involvement is ongoing through his involvement in the wider Nutrition Guidance Advisory Group (NuGAG), which is responsible for developing, on behalf of WHO, guidelines relevant to nutrition.

“One of the things worth noting about that committee is that it has two members from New Zealand and both happen to come from Otago. Professor Murray Skeaff [also from the Department of Human Nutrition] is the other.”

Mann says NuGAG also draws on the expertise of resource people who are responsible for the background work behind the guidelines: including his Human Nutrition colleague Dr Lisa Te Morenga.

“These resource people are actively involved in research in the area in question and are commissioned to undertake the background work necessary to enable committee members like me to make recommendations.

“Lisa has been involved in a significant number of the areas. She is a key resource person and has led about half of the work which has led to the WHO sugar guidelines.”

Te Morenga says WHO has a very proscriptive approach for how to develop nutritional guidelines.

“They need to have the latest evidence summarised in a systematic review, including meta-analysis of the data to underpin all WHO recommendations – so I led the systemic review looking at the effects of dietary sugars on body weight.”

Mann has also been responsible for leading nutritional guidelines for people with diabetes, produced by the European Association for the Study of Diabetes (EASD).

“That was the first group to make evidence-based guidelines for the nutritional management of diabetes.”

Mann says their international guidelines work with WHO is now shifting towards carbohydrate.

“People have been obsessed with protein and fat, and carbohydrate has been the poor relation in terms of academic study. That has changed recently with much more discussion around the positives and negatives of carbohydrate. I think, to a certain extent, we have been influential in putting that point across internationally.”

“We are known as a group that does research in carbohydrate and there are not all that many groups around that have that particular interest," he says. "Certainly, some of the studies for which we are applying for funding could have profound effects on international recommendations in this area.”

Te Morenga says this work will be looking at starchy foods and fibre foods – basically everything that is not fat and protein. Initial work on an HRC-funded systematic review has already identified gaps in the literature that, she says, cannot be answered by the current evidence base.

“That has informed the development of some of the projects that we are hoping to do in the next couple of years – and that is around the importance of the type of carbohydrate that you're recommending if you are comparing a low-carbohydrate diet with a conventional diet.”

Te Morenga has also been involved in work on yet-to-be-released fat guidelines, leading a systemic review on the health effects of saturated and trans-fat reduction in children.

Sodium is the focus of research being undertaken by yet another department member, Dr Rachael McLean, who has been part of an evidence-based review of the Australasian Nutrient Reference Values for sodium intake. She has been working with the WHO Collaborating Centre on Salt Reduction in Sydney, Australia, identifying the best methods for estimating population salt intake in surveys such as the WHO Steps Survey, used around the world to collect nutritional and health information.

“The best way is probably a 24-hour urine test which many people find difficult and is logistically difficult in large population surveys,” she says.

She has also been working with an international team of researchers led from Canada to develop guidelines for best practice in research into sodium intakes and health outcomes, while also looking at how sodium intake might be reduced within the New Zealand population.

“This has focused on the potential benefits of changes in food-labelling help and food composition.” Processed food in a Western style diet is the major factor: breads, cakes and biscuits, breakfast cereals, sauces, pre-prepared meals and takeaways all tend to be high in sodium.

Mann says WHO has issued papers on sodium recommendations which underline the importance of a reduction in sodium intake.

"In terms of WHO headline policies it is one of the nine global targets for reduction of non-communicable disease. Salt was actually ahead of body fatness, so it shows you how important they regard salt to be."