November 2, 2015

expert reaction to study investigating sweetened drink consumption and risk of heart failure in Swedish men

A possible link between sweetened drinks and heart failure in men is the subject of a study published in the journal Heart, with the authors reporting that men who consumed two or more sweetened beverages per day were more likely to develop heart failure than those who were “non-consumers”.

Ms Catherine Collins, Principal Dietitian, St George’s Hospital NHS Trust, said:

“Heart failure is a debilitating and life-restricting condition of increasing incidence in the UK. We know that poorly managed blood cholesterol and blood sugar levels, poorly managed high blood pressure, liver problems from a high alcohol intake, and obesity are the most common factors that increase your risk of developing heart failure. Other causes of heart failure that you personally can do little about include genetic predisposition and exposure to certain infections. So if it’s possible to change your diet to reduce your risk of heart failure, this would be a good thing. Yet the authors of this study generate more questions than they answer – starting with the question asked about sweet tasting drinks in the diet.

““How many soft drinks or sweetened juice drinks do you drink per day or per week”? More to the point – how would you answer this question? This was the 1997 question asked to Swedish men in their 60s, which forms the basis for this claim of sweet-tasting drinks being associated with heart failure. This question included ‘sweet tasting drinks’ – which counted sweetened coffee and sugary drinks – but also sugar-free, low calorie drinks, which are nutritionally very different.

“This study also didn’t report alcohol intake – which is an important dietary factor in heart failure. Nor did it include fruit juices, which provide both calories and fructose – a sugar that may in some circumstances affect metabolism. This is a strange oversight, but probably reflects a ‘state of the art’ approach of some 18 years ago.

“Very little statistical analysis, which ensures that the findings are true and not just a research fluke, appear in this paper – which is of concern. It seems that ‘sweet drinks’ were not particularly related to obesity, to diabetes, or to high blood pressure.

“Usually, if a food or drink is implicated in a health condition, the more you take of it the higher your risk. Yet this study shows that the risk of heart failure was unchanged across most of the usual intake of sweet tasting drinks, with the exception of the highest consumers – those taking more than 400ml of the drinks that ‘counted’ in the study. This is also unusual, as a dietary link often shows an increasing risk with increasing intake.

“Bottom line? This study is hard to interpret as the dietary survey took place nearly 20 years ago, and drinks consumed were different then. They also didn’t include any assessment of alcohol associated liver problems, which is a contributor to risk.

“The study also adds confusion as it includes higher calorie sweetened drinks with their low calorie sweet tasting beverages. It’s possible that these drinks were associated with other, less healthy, dietary choices – but the information isn’t presented. In all, this is a detailed study that lacks important dietary detail – so it’s impossible to suggest any dietary recommendations from this.”

Prof. Francesco Cappuccio, Cephalon Professor of Cardiovascular Medicine & Epidemiology, University of Warwick, said:

“The results of this study are not surprising for those who work in the areas of global burden of disease and action plans to prevent cardiovascular disease globally, but the study does have some limitations as well as strengths. Firstly, a limitation is that the study is an observational study (although prospective) and is unable to ‘prove’ cause-effect relationships. However, a strength is that the sample size is very large, so even small to moderate effects could be detected. Other important limitations are the restriction to men only (no data on women) and the assessment of diet through a Food Frequency Questionnaire rather than direct measurements. This method is unable to measure some important components of the diet (like salt intake) that could be relevant to explain the findings.

“An important observation in this study is that sweetened drink consumption was inversely related to socio-economic status, i.e. more consumption in less educated participants.

“The study reports that those participants who reported >2 servings per day had a 23% increased risk of developing heart failure. So, high sugary drinks can contribute to heart failure by increasing weight gain and diabetes. But an alternative explanation (not discussed in the paper) is that high salt intake (salt intake is higher in low socio-economic groups) increases thirst, hence increased drinking including sweetened drinks. The increase in heart failure could therefore be a consequence of higher salt intake, higher blood pressure and higher heart failure risk (high consumption of sugary drinks would then be a proxy for high salt intake).

“Are there any policy implications? Recent suggestions to include a 20% Sugar Tax on sweetened drinks should be considered seriously, not only to reduce the incidence of obesity but to reduce the overall burden of cardiovascular disease by other mechanisms. In parallel, target-driven food reformulation of salt content should be intensified to further reduce population salt consumption – the main driver of fluid consumption in a population – including sweetened drinks.”

Dr Gavin Sandercock, Reader in Clinical Physiology, University of Essex, said:

“There is currently a lot of discussion around the supposed ill-effects of sugar in science and in the media. The results of this study are very interesting because they show there is no difference in the effects of drinks which do or do not contain any sugar (sweetened vs. artificially sweetened) on the risk of men developing heart failure. The 23% higher risk of developing heart failure is clearly not, therefore, anything to do with sugar per se. The authors quite rightly suggest that drinking more sweetened beverages is simply an indicator of a poor diet overall. The adults who drank two sweetened drinks a day also drank the most coffee, ate the most processed meat, ate the least vegetables and they had more family history of heart disease. Trying to decide if sweetened drinks are the single cause of heart failure is impossible when diet and heart failure are both such complicated issues.

“The difference in drinking habits between the two groups is very small – it’s not two extra cans of fizzy drinks a day, it’s two 200 ml servings, which is less than one bottle. The actual difference in risk of developing heart failure was also very small. Overall, 12 of every 1,000 people who drank no sweetened drinks developed heart failure compared with 15 per 1,000 of those who drank two a day. So sweetened drinks ‘caused’ an extra three cases of heart failure per 1,000 people; compared with the risk associated with genetics, smoking or not exercising, that’s almost nothing.

“It’s important to note that this wasn’t the main aim of the study, and that the study doesn’t include any women; just Swedish men who have very different diets and very different lifestyles to adults in the UK.

“More importantly, the study doesn’t take into account fruit juice, which contains much more sugar than artificially sweetened drinks. Nor does the study include tea or coffee (with or without sugar). In the UK, adults drink much more tea and coffee than they do sweetened beverages so it’s very had to generalise these results to the British population.

“What’s more interesting is that the healthiest group are not those who had no sweetened beverages but those who consumed a small amount – the same patterns as we see in alcohol consumption.”

‘The relationship between sweetened beverage consumption and risk of heart failure in men’ by Iffat Rahman et al. published in Heart on Monday 2 November 2015. 

Declared interests

Ms Catherine Collins: “No COI.”

Prof. Francesco Cappuccio: All unpaid – Head of WHO Collaborating Centre for Nutrition; Member of CASH, WASH, UK National Forum, NACDG of the Faculty of Public Health; Trustee of Student Heart Health Charity; Vice-President of the British Hypertension Society.

Dr Gavin Sandercock declares that he has no relevant interests.