Emily Sonestedt, senior lecturer and associate professor in Nutritional Epidemiology and Suzanne Janzi, doctoral student in Nutritional Epidemiology at Lund University, answer questions about the study which has been published in Frontiers in Public Health.
Which sources of sugar did you analyse?
In this study, we examined sugar sources in three groups:
- Sweetened beverages (soft drinks and fruit drinks but not pure fruit juices)
- Sweet treats (pastries, ice cream, sweets and chocolate)
- Toppings (table sugar, honey, jam and marmalade)
What did you want to investigate?
We wanted to investigate the link between sugar consumption and the risk of various cardiovascular diseases. To do this, we used data from two large cohort studies: the Swedish Mammography Cohort* and the Cohort of Swedish Men**. These studies had used dietary questionnaires, which were collected in 1997 and 2009. We were particularly interested in investigating different sources of added sugar. Toppings are very low in fat and protein, while sweet treats tend to be higher in fat. We hypothesised that sweet treats were more likely to be over-consumed than toppings. Since it has been suggested that liquid sugar metabolises differently in the body than solid sugar and is easier to over-consume, we wanted to study sweetened beverages separately.
What did you find out?
We found that intake of sweetened beverages showed stronger links to cardiovascular disease than any other form of sugar. The group that drank the most sweetened beverages had a significantly increased risk of ischaemic stroke, heart failure, atrial fibrillation and abdominal aortic aneurysm. At the same time, our study shows that for those people who consumed large quantities of sweet treats, there was an inverse relationship. The group that consumed sweet treats occasionally, i.e. more than twice a week, had a lower risk of all the diseases we analysed than those who did not eat any sweet treats at all. For toppings, we saw no clear correlation.
Does this mean that soft drinks are more dangerous than other sources of sugar?
It seems to be easier to obtain large amounts of energy by drinking sugary drinks. Liquid sugar, found in soft drinks and juices, is likely to be less satiating than sugar that is eaten in solid form. This can potentially lead to over-consumption, increasing calorie intake and blood sugar levels. In addition, soft drinks are usually consumed more regularly, making it easier to report how much one drinks, while the consumption of sweet treats can be more difficult to remember.
How can eating occasional treats be beneficial to health?
We saw the highest risk of ill health in those who did not eat any sweet treats at all. This may seem a little odd, but it has been observed in other studies too. We have previously seen the same relationship in another cohort from Sweden, the Malmö Diet and Cancer Study. One reason may be that those who do not eat sugar at all avoid doing so because of health problems, for example. Eating sweet treats occasionally, on the other hand, may indicate a rich social life, which is already known to be a protective factor against disease.
Does your study apply to Swedes, or can the results be applied to other populations?
Our results are based on a Swedish population. Other countries may have different dietary and lifestyle habits than our population. We Swedes are a sweet-loving people and fika is part of Swedish culture. The link with sweetened beverages is fairly well established, but more research is needed to fully understand why different sources of sugar may have different effects on heart health, especially in other parts of the world.
What does it mean to say that you took other factors into account in your study? And what were they?
We know that those who eat a lot of sugar also have other risk factors. We adjusted for a range of factors, such as energy intake, education, BMI, alcohol and smoking. Nevertheless, there were clear links between sugar consumption and risk of ill health.
What does it mean to say that there is no causal link between sugar and cardiovascular disease?
The current study is what is known as an observational study and therefore we cannot really establish a causal relationship. However, previous research has also shown a link between a high consumption of soft drinks and an increased risk of various medical conditions. But it is possible that this is an indirect relationship. That people who consume a large quantity of soft drinks have a more unhealthy lifestyle in general, and that it is therefore not the soft drinks themselves that increase the risk.
