It’s particularly hard to reduce sugar intake over the holiday season, when so many of our social interactions revolve around the consumption of sweet food, says University of Otago Research Fellow Dr Lisa Te Morenga. It’s also difficult when we don’t know, or won’t admit, how much sugar we’re eating. Dr Morenga provided expert advice for a Royal Society of New Zealand paper on sugar and health, which called for better labelling to allow consumers to assess how much added sugar products contain. She tells us about the links between sugar and ill health, how under reporting of sugar consumption makes it difficult to prove those effects, and how a new test can measure long-term sugar consumption by looking at hair.
Do you think people see one piece of research on sugar and feel like they’ve heard it all before?
It would seem that way to me. I can’t believe that anyone hasn’t heard that they should cut back on sugar. It is the nutritional issue of the decade and a lot of other popular dietary advice out there, such as high protein diets, feed into the debate about sugar.
Having said that there is still a lot of misinformation and there are still a lot of people who haven’t thought about it or don’t really care. We did some work with a group of teenagers last year. Some of the teenage girls didn’t even realise that products such as Coke Zero had no sugar in them at all. These teenagers all basically know that sugary drinks are full of sugar, and they know they shouldn’t drink them, but they do it anyway. It’s one thing to inform people, but it’s another challenge to get them to actually change their behaviour.
What makes it so hard for us to stop eating so much sugar?
I worked on one project where we got a group of volunteers to follow the World Health Organisation recommendations for four weeks. We wanted to know if it was easy or hard. We wanted to know why they were consuming a lot of sugar in the first place. They did it, but what was interesting was the number of barriers we have to healthy levels of consumption. There was a lack of awareness about how much sugar was too much. Take a food like jam – we’ve grown up on jam sandwiches and jam on toast. But actually, jam is very high in sugar. That’s also true of many things that you think of as normal breakfast foods.
Also, a lot of our interactions involve the social eating of sugar. In those situations it is very hard for people to say no, there’s a lot of social pressure. In the holiday season this can be especially hard: you are in situations where there are sweet treats and sweet drinks around, you don’t want to seem to be rude or ungrateful, and it can be difficult to have nothing at all.
The higher sugar consumption really occurs in the younger population. We did some work with students and found that when people are studying, when they have a lot of stress, they don’t have time to be organised about meals and it’s much easier to find sugary snacks and drinks. If they’re in the library and they haven’t had a decent dinner, it’s much easier to go find a vending machine than a decent meal. There’s also a tendency to reward ourselves for doing hard things, so you make yourself feel better by having a chocolate bar.
What needs to happen?
We need to stop throwing sugar in people’s faces all the time. The people who hear health messages and take them on board, they tend to be the worried well. I don’t think it’s worth spending a lot of time and effort on making individuals make healthier choices, because what we actually need to do is to get through to the people who don’t really care. The only way I know of to do that is through changes to the food environment, so that it supports their ability to make healthy choices.
We also need to keep researching the links between sugar and health because there are a lot of groups out there with vested interests. We do want to make sure that sugar is having the effect we think it’s having and that we shouldn’t instead be focusing on, say, alcohol instead.
How much is still unknown about the links between sugar and disease?
We’re pretty sure sugar contributes to weight gain, and we’re really sure it contributes to dental decay. All of the other harms, we don’t have strong evidence for those. Every health agency around the world these days would have very similar recommendations around sugar, saying that free sugars – the stuff we add to food – should be limited. But this is based on consistent rather than definitive evidence.
The people making strong claims about the detrimental effects of sugar are basing their opinions on very limited evidence: animal evidence or trials that fed people very high amounts of sugar. The evidence linking sugar to the risk of chronic disease is no stronger than that linking salt to cardiovascular disease. I personally don’t think there’s any magic about sugar. I just think it’s something that tastes really good, we like it, and we tend to overeat it. The problem with overstating the case against sugar is that it will be seen as the only problem in our diet, and focusing on one element can lead people to overcompensate. Also, the idea that health is a single nutrient issue makes it easier for the food industry to replace one unhealthy ingredient with another
One of the reasons it is difficult to definitively link disease with sugar intake is that people tend to under report consumption. This is either because they’ve forgotten, or they don’t notice they are eating these foods, or because it’s socially difficult to admit what you’ve eaten. So one of my main areas of research is around measuring how much sugar people are actually eating, and we’re developing a blood test to do that.
Wouldn’t a blood test only measure short-term sugar intake?
It’s actually a marker of long-term intake because we can measure it in red blood cells, which survive from 90-100 days. So we think it tells us how much sugar has been in someone’s diet over the last three months. This works because although most plants use photosynthesis some have a slightly different pathway, and you can detect the difference in carbon in those plants. It just so happens that cane and corn are two plants that have this different pathway. We pretty much only eat cane as sugar. And corn is often eaten as sugar in the form of high-fructose corn syrup. So by looking at the different carbon signatures within red blood cells we can see a correlation with how much sugar someone has eaten.
We already know from overseas there is a good correlation. In the United States probably a third of their sugar comes from beet, so you won’t be able to detect a high intake of that. And yet they still found a good correlation. We think it would work even better for our population because most of the sugar we eat comes in the form of corn and cane.
We also have some preliminary results looking at hair, because it is also possible to get the marker from there. Hair grows about a centimetre every three months, so longer hair can actually contain a record of sugar consumption over a number of years. This method was originally used by anthropologists to look at the sorts of diets that people might have had historically. But it would be quite a nice, minimally invasive way of testing which would be particularly useful in children.
You wouldn’t do the blood test on an individual level. But it would be useful in large population studies such as the Dunedin Study, which has followed the lives of 1037 babies for over 40 years. That study has never really been able to collect dietary data, because they ask their participants for so much already. But they do get a blood sample taken, so if we can measure this biomarker we can look at people with low intakes of sugar versus high intakes, and compare with things like dental caries as an adult, or the development of heart disease. We might be able to look at how mental health relates to sugar intake. It won’t prove anything, but it will give us lots of interesting information. And if we can be more confident about the links between sugar and disease then policies such as sugar taxation become even hard for the government to refuse.
These interviews are supported by the Royal Society of New Zealand, which promotes, invests in and celebrates excellence in people and ideas, for the benefit of all New Zealanders.
For more information on sugar and health see the Royal Society of New Zealand sugar report.
Feature photo by D Sharon Pruitt.