“Are sugary drinks causing 8,000 cases of diabetes every year?,” the Daily Mirror asks, as a new study estimates they could cause thousands of type 2 diabetes cases in the UK, and millions in the US.
Researchers pooled the results of previous studies to estimate the public health impact of type 2 diabetes associated with sugary drinks consumption, as well as artificially sweetened drinks and fruit juice.
Researchers found that consumption of sugar-sweetened drinks may be linked to 1.8 million cases of type 2 diabetes in the US and 79,000 in the UK over 10 years. They also adjusted their results to take account of body fat (adiposity) and their results suggest that people of a healthy weight may still be vulnerable.
Artificially sweetened drinks and fruit juice also showed a positive association; however, there is thought to be bias associated with this outcome.
As the researchers themselves make clear, this type of study is unable to prove cause and effect.
A government report from July 2015 has recommended that sugar should make up no more than 5% of a person’s calorie intake. Therefore, cutting out sugary drinks entirely could be a good way of doing this.
Where did the story come from?
The study was carried out by researchers from the University of Cambridge, University of Eastern Finland, Tenri Hospital and Kyoto University in Japan, and Harvard T H Chan School of Public Health in Boston. The study was funded by the Medical Research Council Epidemiology Unit Core Support and an American Heart Association postdoctoral fellowship grant.
This study has been widely reported in the UK media. The Guardian and BBC News highlight the fact that slim people may also be vulnerable to the potential harms of sugary drinks.
The Daily Telegraph, the Daily Mirror, Sky News and the Mail Online chose to focus on the potential public health impact estimated in the report: 79,000 new cases of type 2 diabetes in the UK over the course of 10 years and a whopping 1.8 million new cases in the US during the same period.
What kind of research was this?
This type of study is useful in combining the results of smaller trials to draw firmer conclusions; however, the strength of the findings depends on the quality of included trials.
The information gathered was used to produce an estimate of the population attributable fraction (PAF) of sugary drink consumption on the incidence of type 2 diabetes.
A PAF is a measure used by epidemiologists to estimate the effect of a risk factor (in this case, sugary drink consumption) on the incidence of disease (in this case, type 2 diabetes) in groups of people.
The assessment of PAFs is a standard way that public health professionals and policymakers estimate the impact of individual factors on an outcome. This information is used to identify how burden of disease can be reduced.
What did the research involve?
This study searched PubMed, Embase, Ovid and Web of Knowledge for prospective studies of adults without diabetes at the start of the study, published until February 2014. Data was synthesised using meta-analysis and survey analysis for the PAF associated with the consumption of sugar-sweetened drinks. Data was extracted from selected studies, including:
- baseline personal information (e.g. body mass index)
- duration of follow-up
- exclusion criteria
- sample size
- loss to follow-up
- assessments of beverage consumption
- incidence of type 2 diabetes
- types of beverage consumed
Main exposures assessed were:
- sugar-sweetened drinks, which were any sweetened drink, including sugar-sweetened fruit juice, that are not presented as diet or non-caloric
- artificially sweetened drinks, including low-caloric soft drinks
- fruit juice, either 100% fruit juice, or fruit juice assessed separately from fruit drinks
An estimation of PAF was then calculated. The confounding effect of body fat (adiposity) was adjusted for.
What were the basic results?
The study included 17 cohorts, comprising 38,253 cases of type 2 diabetes.
National surveys in the US from 2009-10 and the UK from 2008-12 were used to determine the PAFs. This consisted of a sample of 4,729 US adults and 1,932 UK adults over 20 years without prevalent diabetes, representing 189.1 million US adults and 44.7 million UK adults.
Meta-analysis found a link between higher consumption of sugar-sweetened drinks and a greater incidence of type 2 diabetes. One drink per day was associated with an 18% greater incidence in type 2 diabetes before adjusting for body fat, and 13% after adjustment. Similarly, artificially sweetened drinks showed an association with a 25% increase in incidence per one drink per day before adjustment and 8% after; for fruit juice, it was 5% and 7% after adjustment.
The consumption of sugar-sweetened drinks occurred in 54.4% of people in the US and 49.4% in the UK.
If the assumption is made that sugar-sweetened drinks are the cause of type 2 diabetes, independent of obesity status, this would result in 1.8 million cases of type 2 diabetes in 10 years in the US and 79,000 cases in the UK. The findings also showed that young adults and men have greater numbers of type 2 diabetes due to sugar-sweetened drinks than older adults and women.
How did the researchers interpret the results?
The researchers conclude that, “Habitual consumption of sugar sweetened drinks was associated with a greater incidence of type 2 diabetes, independently of adiposity. Although artificially sweetened drinks and fruit juice also showed positive associations with incidence of type 2 diabetes, the findings were likely to involve bias. None the less, both artificially sweetened drinks and fruit juice were unlikely to be healthy alternatives to sugar sweetened drinks for the prevention of type 2 diabetes.”
This study is a systematic review and meta-analysis that aimed to investigate the associations between consumption of sugar-sweetened drinks, artificially sweetened drinks, and fruit juice with type 2 diabetes, and to estimate the PAF for type 2 diabetes in the UK and US.
Regular consumption of sugar-sweetened drinks was associated with increased incidence of type 2 diabetes.
Artificially sweetened drinks and fruit juice also showed a positive association; however, there is thought to be confounding and publication bias associated with these outcomes.
Consumption of sugar-sweetened drinks may be linked to 1.8 million cases of type 2 diabetes in the US and 79,000 in the UK over 10 years, if we assume causality. However, this study did not prove cause and effect.
Diabetes is a growing problem, with around 3.2 million people aged 16 or over diagnosed with diabetes in England in 2013, and 630,000 people who have not been diagnosed. This is expected to increase. The rise in type 2 diabetes is mostly down to:
- increasing levels of obesity
- lack of exercise
- increase in unhealthy diets
- an ageing population
Preventative measures against type 2 diabetes can be taken, such as being more active, losing weight and eating more healthily.
Recent recommendations from the Scientific Advisory Committee on Nutrition (SACN) state that free sugars should not exceed 5% of our total dietary energy intake. This applies to all age groups from 2 years upwards. This means
- no more than 19g a day of free sugars for children aged 4 to 6
- no more than 24g a day for children aged 7 to 10
- no more than 30g a day for children aged 11 or more and adults
No specific recommendations are made for children under the age of 2, because of an absence of information. However, from about 6 months of age, a gradual change to a more diverse diet that includes more wholegrains, pulses, fruit and vegetables is encouraged.
Sugary drinks can make up a large proportion of sugar intake and these should be consumed in moderation or, ideally, not at all. As always, maintaining a healthy weight, eating a balanced diet, moderating your alcohol consumption and taking regular exercise will reduce the risk of a range of chronic diseases.