Sugar-sweetened sodas and other drinks — including 100 percent fruit juice — may raise the risk of developing some cancers, according to the findings from a large French study published this week in The BMJ.
Specifically, the study found that drinking as little as three-and-a-half ounces of sugary beverages a day — about a third of a typical can of soda — was associated with an 18 percent increase in the overall risk of cancer.
For women, drinking that amount of soda was linked to a 22 percent increased risk of breast cancer. Those increased risks correspond to about an extra four cases of cancer among every 1,000 people over a five-year period.
This was an observational study, so it can’t prove cause and effect. It’s also difficult to isolate the impact that a single element of a person’s diet has on his or her health. But this is not the first time that researchers have linked the consumption of sugar-sweetened drinks with serious health risks. Other research has found strong associations between the regular consumption of sugary drinks and an increased risk of high blood pressure, heart disease and type 2 diabetes.
Health officials, including those at the American Cancer Society (ACS), have long advised people to cut down on sugary beverages — including fruit juice — because of the evidence linking them to excess weight, which is a major risk factor for cancer.
But, as Colleen Doyle, managing director of nutrition and physical activity at the ACS, told Consumer Reports, “what makes this new study unique is it’s the first one of its kind to suggest a direct link — that it’s sugar itself, whether it’s added or from natural sources like fruit juice, that is the problem.”
For the current study, researchers analyzed dietary and health data collected from 101,257 French adults, who were participants in an ongoing nutrition survey called NutriNet-Sante. The participants for this particular study were followed for up to nine years (2009-2018), and during that time they provided an average of five reports of the foods they ate — and drank.
Almost 80 percent of the participants were women, and they had an average age of 42 when the study began. None had been diagnosed with cancer when they were enrolled in the study.
Using the participants’ dietary reports, the researchers calculated the participants’ daily consumption of both sugar-sweetened and artificially sweetened (“diet”) beverages. The sugary drinks included sodas (carbonated and not), sports drinks, energy drinks, 100 percent fruit juices, fruit drinks, syrups, sugar-sweetened hot beverages and milk-based sugar-sweetened beverages.
The amount of sugary drinks consumed by the people in the study ranged from an average of 3.1 ounces to 6.2 ounces per day. Men tended to drink more of the beverages than women.
After taking into account a variety of factors that can affect cancer risk (such as age, body mass index, physical activity, chronic health conditions and family history of cancer), the researchers found that the participants who drank more sugary drinks were more likely to have developed cancer.
For every 3.4 ounces of sugary drinks the participants consumed daily, their risk of developing any kind of cancer increased by 18 percent — and the women’s risk of developing breast cancer climbed by 22 percent — compared to participants who drank less than 3.4 ounces per day.
The researchers found no increased risk, however, for two other specific cancers that they focused on in the study — prostate and colorectal.
They also found no link between artificially sweetened drinks and an increased risk of cancer, although the researchers caution that the amount of these beverages consumed in the study was low, which makes that finding less reliable.
Limitations and implications
Again, this study can’t prove a direct connection between the consumption of sugary drinks and an increased risk of cancer. Also, the study was conducted in France and involved mostly women. The results might be different in a more diverse population.
Still, the study’s design is robust enough to make its findings troubling.
As the study’s authors point out in their paper, there are several possible biological mechanisms that may explain why sugary drinks increase the risk of cancer. Those include the effects that sugar has on insulin resistance and on the buildup of visceral fat (the fat that enwraps vital organs in the abdomen) — factors that have been linked to the formation of malignant tumors.
“As usual with nutrition, the idea is not to avoid foods, just to balance the intake,” said Mathilde Touvier, the study’s senior author and research director of Inserm, the French public health research center that oversees the NutriNet-Sante database, in an interview with Guardian reporter Sarah Boseley.
“The recommendation from several public health agencies is to consume less than one drink per day,” she added. “If you consume from time to time a sugary drink it won’t be a problem, but if you drink at least one glass a day it can raise the risk of several diseases — here, maybe cancer, but also with a high level of evidence, cardiometabolic diseases.”
For more information: You can read the study in full on the BMJ’s website.