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A new observational study finds a link between the consumption of sugary drinks, including 100% fruit juices, and the risk of cancer.
Known health risks of sugary drinks
Obesity, type 2 diabetes, and cardiovascular disease are only some of the conditions that previous studies have associated with sweetened drinks. Some studies in rodents have suggested that the added sugar in soft drinks can drive the spread of cancer and fuel tumor growth.
Now, new research further explores the link between sugary drinks and cancer. The observational study, appearing in The BMJ, finds an association between high intake of sugary drinks and cancer. Eloi Chazelas, from the Sorbonne Paris Cité Epidemiology and Statistics Research Center in France, is the first author of the study.
Sugary food/drinks have negative side effects on your focus during tests. Consume healthy choices such tea, coffee, fruit & nuts for finals.
— LSU Center for Academic Success (@LSU_CAS) May 6, 2014
How much sugar is too much sugar?
According to the American Heart Association (AHA), the maximum amount of added sugars you should eat in a day are:
- Men: 150 calories per day (37.5 grams or 9 teaspoons)
- Women: 100 calories per day (25 grams or 6 teaspoons)
To put that into perspective, one 12-oz can of Coke contains 140 calories from sugar, while a regular-sized Snickers bar contains 120 calories from sugar.
In contrast, the US dietary guidelines advise people to limit their intake to less than 10% of their daily calorie intake. For a person eating 2,000 calories per day, this would equal 50 grams of sugar, or about 12.5 teaspoons.
Read more: Is sugar really addictive?
Studying sugary drinks and cancer risk
Chazelas and team examined the links between the intake of sugary drinks and various forms of cancer in 101,257 French adults aged 42 years, on average. The researchers obtained the data from the NutriNet-Santé study.
Among all these cases were 693 of breast cancer, 291 of prostate cancer, and 166 colorectal cancer.
The drinks they examined included “sugar-sweetened beverages” such as soft drinks, syrups, fruit drinks, 100% fruit juices without any added sugar, milk-based sugary drinks, sports drinks, and energy drinks. The researchers also considered artificially-sweetened drinks, that is, “all beverages containing nonnutritive sweeteners, such as diet soft drinks, sugar-free syrups, and diet milk-based beverages.”
Using 24-hour online food questionnaires, the researchers assessed the participants’ consumption of 3,300 different kinds of foods and drinks. Furthermore, clinical observation of the participants continued for up to 9 years.
During this time, the researchers looked at the risk of “overall, breast, prostate, and colorectal cancer.” Chazelas and colleagues accounted for potential confounders, including age, sex, education, hereditary risk of cancer, and lifestyle factors — such as smoking behaviour and exercise patterns.
A 22% higher risk of breast cancer
Over the follow-up period, 2,193 people developed cancer for the first time; they were 59 years old at the time of diagnosis, on average. Among all these cases were 693 of breast cancer, 291 of prostate cancer, and 166 colorectal cancer.
The analysis revealed that for a daily increase of 100 millilitres in the intake of sugary drinks, the risk of overall cancer rose by 18%, and the risk of breast cancer increased by 22%. When the researchers analyzed the risk for 100% fruit juices separately, these also elevated the risk of overall cancer and breast cancer.
The findings may not be widely generalizable, as the study cohort is not representative of the wider population, they continue.
However, the study found no links with colorectal cancer or prostate cancer. By contrast, diet drinks did not increase cancer risk. The scientists explain that people who consumed diet drinks did so in very small amounts, so they suggest interpreting this particular result with caution.
Chazelas and colleagues also lay out the strengths and weaknesses of their research. First, the “large sample size and its detailed and up-to-date assessment” of the drinks consumed to strengthen the results, write the researchers. However, the findings may not be widely generalizable, as the study cohort is not representative of the wider population, they continue.
“Since the participants of the NutriNet-Santé cohort were more often women,” they say, “with health-conscious behaviours and higher socio-professional and educational levels than the general French population, this might have resulted in a lower cancer incidence compared with national estimates.”
"The study found the highest quarter for sugary drink consumption had a 30% higher risk for cancer, and a 37% higher risk for breast cancer…"
Well, that's terrifying — "sugary drinks" includes 100% fruit juices. https://t.co/RIPqCQg2Wy
— klia (@klia00) July 12, 2019
Other limitations include the inability to determine causality and potential measurement biases. However, the authors speculate that sugary drinks may raise cancer risk because the sugar affects visceral fat, blood sugar, and inflammatory markers — all of which previous studies have correlated with higher cancer risk.
The researchers conclude
“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.”