Heavy consumption of sugary drinks may raise the risk of developing bowel cancer before the age of 50, according to a major study into diet and disease in US nurses.
Researchers analysed dietary and medical records of more than 95,000 women tracked from 1991 to 2015 as part of the US Nurses’ Health II study and looked for evidence linking sugary drinks to early diagnosis of bowel cancer.
The scientists reported that women who consumed more than a pint of sugary drinks a day were twice as likely over the course of the study to be diagnosed with early onset bowel cancer than those who drank less than half a pint a day.
Given that sugary drinks are already known to be bad for health – by driving up rates of obesity and type 2 diabetes – the researchers at Washington University in St Louis said their results provided another reason not to consume too much. “Our findings reinforce the public health importance of limiting sugar-sweetened beverage intake for better health outcomes,” they wrote in the journal Gut.
But some scientists not involved in the work said the findings were tentative because only 109 women who enrolled in the study were diagnosed with early onset bowel cancer, and among them only 16 reported drinking more than a pint of sugary drinks a day. Eating red and processed meat, a diet low in fibre, smoking, drinking alcohol and being overweight have all been found to raise the risk of the disease, and these can be hard to fully account for, they said.
“We just can’t be sure whether the observed association between sugary drinks and bowel cancer under the age of 50 is one of cause and effect,” said Kevin McConway, an emeritus professor of applied statistics at the Open University.
Bowel cancer is one of the most common cancers in the UK and, while only 5% of cases in men and 7% in women are in the under 50s, rates in these younger people have been increasing steadily for the past two decades. In 2019, a major French study found evidence that sugary drinks may raise the risk of various cancers.
To look at whether the consumption of sugary drinks in adolescence could play a role in rising rates of bowel cancer, the researchers analysed questionnaires that 41,000 of the women completed on their drinking habits when they were 13 to 18 years old. According to the study, for every daily sugary drink, measuring 350ml, the risk of developing bowel cancer before 50 years of age rose by 32%.
But again, some scientists believe more studies are needed to confirm the effect. “The analysis is based on only six cases of cancer found in this group. This is too small to draw any strong conclusions,” said Dr Carmen Piernas, a nutrition scientist at the University of Oxford.
Duane Mellor, a dietitian at Aston University, said that while reducing sugary drink intake might lower the risk of bowel cancer, it may have little effect without also improving lifestyle and overall diet.