February 3, 2014

expert reaction to new research into added sugar and cardiovascular disease

A study in JAMA Internal Medicine reported consumption of added sugar, found in processed and prepared foods, was associated with increased risk for death from cardiovascular disease.

Victoria Taylor, Senior Heart Health Dietitian at the British Heart Foundation, said:

“Sugar is a hot topic in the press at the moment and this study is another reminder to keep an eye on the amount of added sugar in our diet.

“Added sugar can mean extra calories, which can lead to weight gain. So try to keep sweet snacks and fizzy drinks as occasional treats rather than everyday staples.

“However, this research highlights an association, which is not the same as saying sugar causes cardiovascular disease. It’s also important to remember that UK sugar intakes and dietary guidelines are different to those in America.

“Although we’re hearing a lot about sugar at the moment, it’s important not to lose sight of your diet as a whole.  Rather than focusing on single nutrients, aim for a balanced diet and pair it with plenty of exercise.”

Dr Nita Forouhi, Programme Leader, Medical Research Council Epidemiology Unit, University of Cambridge:

“The issue is more complicated than a binary “all sugar is bad” or “sugar is not the culprit”. But Yang and colleagues’ work on the link between added sugar consumption and cardiovascular risk using nationally representative data in the US is both comprehensive and credible.

“Dwelling on the current limitations of dietary medical research, one could wait a long time for the near-unobtainable goal of a perfect research study with irrefutable findings, but what is sure here and now is that Yang and colleagues’ work adds to the mounting evidence for the many health risks of the high consumption of added sugars.

“Given the information Yang and colleagues provide that the source of nearly 50% of total added sugars in the US is from sugar sweetened beverages and fruit drinks, their study provides support that these represent the “low hanging fruit” for first wave of public and policy action. Clear front of pack labelling of sugar content for informed choice by consumers is a logical step. While policy makers deliberate on the pros and cons of a sugary drinks tax, there is a public health action less talked about: a health warning on soft drinks with high sugar content, recommending to limit consumption as part of a healthy diet.

“There are three key strands of findings in Yang et al’s work. First, consumption of added sugar is higher than recommended among most Americans, and there is ethnic disparity, with highest consumption among black Americans. Second, they provide confirmatory evidence of increased cardiovascular risk with regular consumption of sugar sweetened beverages. Third they provide novel evidence for the cardiovascular harms of total added sugars over and above the past research focus on sugary drinks.”

Additional information from Dr Nita Forouhi:

“There are three things we need to understand:

1. The findings cannot be used to consider individual level risk, and the findings cannot be applied to all individuals equally, because the study did not find the risk of cardiovascular deaths to be uniform across different strata of the population. For instance, they did not observe this increased risk to be significant among men, or among black Americans (while this group had the largest consumption of added sugar).

2. The study did not prove a causal association between sugar consumption and risk of cardiovascular death – i.e. no cause and effect is shown; an association is shown.

3. We have to place the findings in context that the study results tell us about “relative risks” that compare the death rate in people who consume more than 25% versus less than 10% of total calories in the form of added sugar. In terms of “absolute risk” of cardiovascular deaths, this will vary according to an individual’s risk due to other factors. For a person whose risk of CVD death is, say, 5% over 10 years, consuming more than 25% versus less than 10% of calories as added sugar, would increase their absolute risk of cardiovascular death to around 13%, i.e. an increase in absolute risk of about 8%, if nothing else changes. Among very important risk factors for cardiovascular disease are smoking, cholesterol level, blood pressure level, family history of the condition, obesity and other factors.

“What we can say is that this study lends support to a growing body of evidence that higher sugar consumption is potentially harmful for health, this study focusing on risk for cardiovascular death. The study has some limitations, and the effects may be more modest in reality than those reported, due to confounding factors (alternative explanations for the findings), but even after that overall there is a positive association between higher total added sugar consumption and risk of CVD death. Further research will help to answer the issues more specifically.”

Prof Patrick Wolfe, Professor of Statistics, University College London (UCL), said:

“This study reports an inferred association, based on estimated dietary intakes of added sugar, between an increased percentage of calories from added sugar, and an increased risk of CVD mortality. In a qualitative sense the results are perhaps not that surprising. However, it is worth noting that these findings are not the same as a causal if/then claim, and rightfully the authors note this in the last line of their discussion section. It is also worth noting that this study is a population-level comparison of different groups based on the categories of added sugar estimated to be in the respective groups’ diets – it is not equivalent to saying that a given individual’s risk goes up by the inferred population-level amount. Thus, standard caveats for this kind of statistical analysis apply. One way to think about it is to imagine two idealised “average” representatives of these populations, identical in all aspects save for their “extremely low/high” added sugar numbers; the study is reporting the best estimate, given the data, of the increased risk of CVD mortality of one extreme relative to the other.”

Prof David Spiegelhalter, Winton Professor of the Public Understanding of Risk, University of Cambridge, said:

“I echo the points made by Prof Wolfe, but also add that the comparison of the group getting “<10%” of their calories from added sugar with the group getting “>25%” of calories from added sugar, is more accurately a comparison between “5%” and “30%” since these are the median values within these bands.  Figure 1 in the paper shows that 5% and 30% are at the very ends of the population distribution, so the hazard ratio of 2.75 (Table 3) is comparing the extreme ends of the population. Figure 1 shows that the increased hazard for moderately different groups is not that great.

“My conclusions are:

(a) people at the extreme high end of added-sugar consumption (around 30%) appear to have around 3 times the annual risk of dying from a heart attack than those at the extreme bottom end (around 5%), even allowing for other differences between these groups.

(b) this does not necessarily mean that if you suddenly change from consuming hardly any added sugar to shovelling down huge amounts, your will increase your risk by this much. But it probably won’t do you any good.

(c) Getting the population to cut down added sugar will have a substantial benefit to public health, but each individual may not benefit much.”

Prof Naveed Sattar, Professor of Metabolic Medicine, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, said:

“We have known for years about the dangers of excess saturated fat intake, an observation which led the food industry to replace unhealthy fats with presumed ‘healthier’ sugars in many food products. However, the present study, perhaps more strongly than previous ones, suggests that those whose diet is high in added sugars may also have an increased risk of heart attack.  Of course, sugar per se is not harmful – we need it for the body’s energy needs – but when consumed in excess it will contribute to weight gain and, in turn, may accelerate heart disease. Some will argue that the evidence is not sufficiently strong to warrant policies to limit sugar intake. However, the potential to reduce sugar intake by targeting sugar sweetened beverage consumption is readily achievable and would be an excellent first step in the battle to reduce the excessive intake of sugar.

“This new study is interesting but such an observational study can never prove excess sugar per se causes heart attacks – it may have also been something else an individual’s diet or lifestyle that explains this excess risk, which is hard to say for certain. However, to ignore the mounting evidence for the adverse health effects of excess sugar intake would seem unwise. Helping individuals cut not only their excessive fat intake, but also refined sugar intake, could have major health benefits including lessening obesity and heart attacks. The first target, now taken up by an increasing number of countries, is to tax sugar rich drinks. Whilst this may seem a blunt instrument, the food and drink industry are able to make positive changes in their food formulations and still remain very profitable. Ultimately, there needs to be a refocus to develop foods which not only limit saturated fat intake but simultaneously limit refined sugar content.”

‘Added Sugar Intake and Cardiovascular Diseases Mortality Among US Adults’ by Yang et al. published in JAMA Internal Medicine on Monday 3 February.