A study published by The BMJ shows a significant association between higher consumption of sugary drinks – including fruit juices – and an increased risk of cancer. Just 100ml per day was linked to an 18% increased risk of overall cancer.

The French team behind the study say that the findings add to a growing body of evidence indicating that limiting sugary drink consumption, together with taxation and marketing restrictions, might contribute to a reduction in cancer cases.

Despite this growing evidence base, direct research on sugary drinks and the risk of cancer remains limited.

So a team of researchers based at the Sorbonne University in Paris set out to assess the associations between the consumption of sugary drinks (sugar sweetened beverages and 100% fruit juices), artificially sweetened (diet) beverages, and risk of overall cancer, as well as breast, prostate, and bowel (colorectal) cancers.

Their findings are based on 101,257 healthy French adults.

Participants completed multiple dietary questionnaires, designed to measure usual intake of 3,300 different food and beverage items, and were followed up over a nine year period, 

Daily consumption of sugary drinks (sugar sweetened beverages and 100% fruit juices) and artificially sweetened (diet) beverages were calculated and first cases of cancer reported by participants were validated by medical records and linked with health insurance national databases.

Several well known risk factors for cancer, such as age, sex, educational level, family history of cancer, smoking status and physical activity levels, were taken into account.

During follow-up ,193 first cases of cancer were diagnosed and validated (693 breast cancers, 291 prostate cancers, and 166 colorectal cancers).

“The results show that a 100 mL per day increase in the consumption of sugary drinks was associated with an 18% increased risk of overall cancer”

The results show that a 100 mL per day increase in the consumption of sugary drinks was associated with an 18% increased risk of overall cancer and a 22% increased risk of breast cancer.

When the group of sugary drinks was split into fruit juices and other sugary drinks, the consumption of both beverage types was associated with a higher risk of overall cancer. No association was found for prostate and colorectal cancers.

In contrast, the consumption of artificially sweetened (diet) beverages was not associated with a risk of cancer, but the authors warn that caution is needed in interpreting this finding owing to a relatively low consumption level in this sample.

The researchers have urged caution on the way their findings are interpreted, pointing out that their study is an observational one, so can’t establish cause. 

Possible explanations for these results include the effect of the sugar contained in sugary drinks on visceral fat (stored around vital organs such as the liver and pancreas), blood sugar levels, and inflammatory markers, all of which are linked to increased cancer risk. Other chemical compounds, such as additives in some sodas might also play a role, they add.

Nevertheless, the study sample was large and the French team was able to adjust for a wide range of potentially influential factors. What’s more, the results were largely unchanged after further testing, suggesting that the findings withstand scrutiny.

These results need replication in other large scale studies, say the authors.

“These data support the relevance of existing nutritional recommendations to limit sugary drink consumption, including 100% fruit juice, as well as policy actions, such as taxation and marketing restrictions targeting sugary drinks, which might potentially contribute to the reduction of cancer incidence,” they conclude.

“we can speculate that the mechanism may be related to an increased risk of obesity….or perhaps to the frequent spikes in blood sugar levels that may be associated with habitual consumption of such drinks”

UK-based scientist Ian Johnson, of the Quadram Institute Bioscience, told The Times that consumption of sugary drinks might be “acting as a marker for some other unidentified aspect of a dietary pattern linked to higher risk of cancer.”

He added: “But if we assume that a real causal link between consumption of sugary drinks and cancer does exist, then we can speculate that the mechanism may be related to an increased risk of obesity, which is a well established risk-factor for various types of cancer, or perhaps to the frequent spikes in blood sugar levels that may be associated with habitual consumption of such drinks.”

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