EXPERT REACTION: Are sugary drinks giving you cancer?

The paper by Chazelas et al, which is published in BMJ, shows a disturbing increase in the risk of some cancers associated with the intake of sugar-sweetened beverages.

While the increased risk was relatively modest, the work comes from a large cohort study, including five years follow up.

In addition to sugar-sweetened beverages, 100% fruit juices were also found to increase the risk, but importantly, no such relationship was observed for artificially sweetened beverages.

This association between sugary drinks and the risk of cancer might be explained in part by their effect on overweight and obesity, which are known to be a risk factor for certain cancers, however the link held following adjustment for body mass index or weight change.

The authors conclude that the sugary drinks widely consumed as part of our so-called ‘western’ diet represent an opportunity for cancer prevention.

This work adds to the evidence for detrimental impacts of sugary drinks, and will provide impetus for other large scale studies, as well as work investigating the possible underlying mechanisms.

The Australian Dietary Guidelines recommend limiting sugar intake and focusing on drinking water and milk, and this paper adds to the body of evidence that recommends that consumption of sugar-sweetened drinks should be limited as they are not good for our health.

Research also suggests that soft drinks increase the risk of tooth decay, impact fertility and can contribute to excess calorie consumption. Sugar intakes in Australia have been falling over the past few decades, however around one in every two Australian adults consume soft drinks at least once per week, so there is definitely room for improvement.  
 
We do, however, need to remember that the risk of cancer is increased by many other factors too, so although it is worth reducing your consumption of sugar-sweetened beverages, it’s essential to look at your whole dietary intake and lifestyle.

While this paper shows an interesting possible association between sugary drinks consumption and cancer risk, there are so many caveats to this type of study design that the findings should be just viewed as interesting and hypothesis generating, rather than meaningful in terms of establishing any actual link, as the authors themselves concede.

To suggest that 'Findings suggest limiting sugary drinks might contribute to a reduction in cancer cases, say researchers' [from the BMJ press release] goes well beyond the ambit of this paper and is a gross over extrapolation of the results, even when tempered by the use of the word 'might' in the statement.

What is needed is a better understanding of what might be driving this apparent association, for example if the people drinking the extra sugar were not necessarily more overweight than the controls then this must mean they were consuming less calories in solid food, all things being equal. So it is just as plausible that this could be the true explanation for the effect, as less solid food might translate to less plant based antioxidants and other anticancer molecules. This is consistent with their data showing that, compared with lower consumers of sugary drinks, higher consumers tended to have higher energy, carbohydrate, lipid, and sodium intakes and lower alcohol intake, compared with lower consumers.  Hence a more plausible explanation might be that intake of sugary drinks is just a marker of someone with an overall poor diet and this poor diet is actually  what is driving cancer risk.

The article does highlight one important point which is commonly missed, high sugar natural fruit drinks which are flourishing worldwide and being marketed  as a 'healthier option' by juice and smoothie companies can be just as bad if not worse than the carbonated drinks they are attempting to replace as in many cases they can have an even higher total sugar content. The population continues to be conned into thinking that 'natural' automatically equates to 'healthier' which is simply not the case.

A new large study, published in the British Medical Journal, reports that sugary beverages, including soft drinks but also 100% fruit juice, increase overall cancer risk.

It involved over 100,000 French adults with an average age of 42 years who were followed for nine years. During this time they recorded consumption of over 3,000 different food and beverage items. During the follow-up period over 2,000 cancers were diagnosed for the first time, with age 59 years being the average age of diagnosis.

For each 100 ml increase per day in sugary drink consumption, there was an 18% increase in overall cancer. Women represented 79% of subjects and this amount of sugary drink consumption increased breast cancer by 22%. For higher consumption there was proportionately higher cancer risk.

100% fruit juice with no added sugar posed the same cancer risk as sugary soft drinks.

Diet beverages did not increase cancer risk. Like sugar, they do, however, increase the risk of diabetes and heart disease, as shown in numerous previous studies.

The workers took numerous other factors into account in their data analyses, so increasing the reliability of their findings.

They suggested that the mechanism involved a sugar-induced increase in fat surrounding vital organs in the body, particularly the liver and pancreas, as well as in insulin resistance, and inflammation inside the body. All of these are linked to cancer risk.

The link with cancer is probably worse than the study found. This is because the subjects studied were on average at the upper level of educational and socioeconomic level and thus had a relatively healthy diet and lifestyle than the rest of the population. Longer follow-up and studies with more men might be expected to detect a link with other cancers.

The researchers said that their findings add to calls for a tax on sugary drinks, bans on advertising, restrictions on marketing, to which I would add education starting with parents and children and the removal of vending machines that dispense unhealthy ‘food’,  i.e., a similar combination of approaches that have proven so effective in cutting the smoking rate.

While the association between the consumption of sugary drinks and an increasing number of cancers was known, this study is the first to convincingly link these drinks directly to cancer risk. Much of the cancer risk is likely to arise via obesity. This points once again to the need to reduce the consumption of sugary drinks for health.

Sugar should be treated much like alcohol and tobacco. While an information campaign would be helpful, it is unlikely to have a significant impact on its own. Taxation and advertising restrictions are probably also needed. Modelling studies have shown that both can lead to large improvements in health. They are likely to be good for the economy too: a healthy population is a more productive population.

As Adam Smith, often considered the founding father of economics, wrote in ‘The Wealth of Nations’ in 1776: 'Sugar, rum, and tobacco, are commodities which are nowhere necessaries of life, [but] which are ... objects of almost universal consumption, and which are therefore extremely proper subjects of taxation.

Our study demonstrated a clear link between sugary soft drink consumption and obesity-related cancers. The more sugary soft drinks participants drank, the higher their risk of cancer. This was not the case for diet soft drinks, suggesting the high levels of sugar in these drinks were a key contributor.

While there were differences in our cohort study and the French cohort, in terms of age and obesity status, the results clearly show the impact of sugary drink consumption on cancer risk.

Today's findings add weight to the growing evidence of the link between consuming sugary drinks and cancer risk. 

We hope that this new research will educate people about the health risks associated with these drinks, and encourage them to reduce their consumption.

The findings reflected those from a similar Australian study conducted by Cancer Council Victoria and the University of Melbourne, adding to the mounting evidence that the high levels of sugar in these drinks are contributing to cancer, and other chronic diseases.
 
Sugary drinks are the largest source of added sugar in Australians’ diets, and these drinks are already known to be a cause of obesity, which greatly increases the risk of 13 types of cancer.
  
Governments have a role to play in regulating the marketing and availability of these drinks. 
 
It’s virtually impossible to escape the enormous amount of marketing, price promotions and sponsorship by sugary drink companies. Young people drink more of these drinks than anyone else and corporations have created this demand and continue to bombard them with marketing on TV, social media and public transport. We need government controls around unhealthy marketing to protect children and young people from its pervasive influence. We also need to take sugary drinks out of schools, recreation facilities and hospitals to protect people and promote healthier options.
 
A 20 per cent health levy on sugary drinks would deter people from these cheap and very unhealthy drinks. Funds raised could be used to promote healthy eating in our community, in time reducing the cancer burden and associated health costs.