We have now found that drinking at least one sugar-sweetened beverage every day is linked to a much higher risk of developing stomach cancer in a long-term study of more than 112,000 US adults.
The researchers at Mass General Brigham Cancer Institute examined dietary, lifestyle, and health information collected over several decades. Those who had at least one serving of a sugar-sweetened beverage every day had a 2.45 times higher risk of gastric cancer compared to those who consumed less than one serving a month.
The results are published in Gastro Hep Advances. While the results indicate a possible dietary association, this study does not show that sugary drinks cause stomach cancer directly.
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The study also tracked more than 112,000 people.
The researchers analyzed data from 112,284 participants enrolled in two long-running US health studies, the Nurses' Health Study and Health Professionals Follow-Up Study.
The studies collected detailed information on participants' diets, lifestyles, and health for many years. In the follow-up period, 278 participants developed gastric cancer.
The study found that people who had at least one sugar-sweetened beverage per day had 2.45 times the risk of gastric cancer compared to those who drank less than once a month.
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The association was observed in men and women too.
Further, the researchers analyzed total fructose consumption. Higher fructose consumption was associated with a higher incidence of gastric cancer. Fructose is a major source of sugar in many sweetened beverages.
Among women in the Nurses' Health Study, drinking more than one sugar-sweetened beverage per day was associated with a 3.04-fold higher risk than women who rarely consumed these drinks.
What counts as a Sugary Drink?
The study focused on sugar-sweetened beverages rather than all drinks containing artificial or naturally occurring sweeteners.
Researchers classified carbonated beverages, punch, lemonade and sports drinks as sugar-sweetened beverages. Artificially sweetened beverages, like low-calorie carbonated drinks, were studied separately.
Importantly, the study did not find a similar association between artificially sweetened beverage consumption and gastric cancer when the authors accounted for other factors.
That does not mean artificially sweetened drinks have been proven to be risk-free. It simply means that this study did not find an increased incidence of gastric cancer associated with their consumption.
Why could Sugary Drinks Lead to Stomach Cancer?
Researchers said that more work is needed to understand the biological mechanisms of the association.
One potential area of interest is fructose. Higher total fructose intake was also linked with higher gastric cancer incidence. There are also studies on the relationship between high sugar intake, metabolic changes and inflammation, but these factors do not show that sugary beverages directly cause stomach cancer.
The researchers also tested for Helicobacter pylori, also known as H. pylori. The bacterium is a risk factor for stomach cancer, and researchers assessed H. pylori in 940 participants.
Almost one-third of the participants had evidence of H. pylori infection. But researchers did not find an association between sugar-sweetened beverage consumption and H. pylori infection.
This means that the association between sugary drinks and gastric cancer cannot be explained simply by sugary beverages being linked to H. pylori infection in that subset.
Study Does Not Prove Sugary Drinks Cause Cancer
And yet even with that number of findings, the findings should also be taken very seriously.
The study was observational, which means that researchers were looking at trends in existing health and dietary data and not forcing people to consume or avoid sugary beverages. Such studies do suggest associations but are not a direct cause-and-effect relationship.
People who drink sugary beverages regularly can also differ in other ways from the infrequent consumers in diet, body weight, physical activity, and other lifestyle factors. The researchers adjusted for a number of possible confounders, but observational studies can’t exclude the potential for other factors.
The study also involved participants from two US health professional cohorts, so the results may not necessarily apply to every population or country in the same way.
Further study is needed to assess whether the association is replicated in other populations and what the mechanisms are that could explain it.
What Does That Mean For Your Diet?
The findings buttress concerns that people regularly consume large amounts of sugar-sweetened beverages.
Sugary drinks can add much more sugar to the diet than whole foods do without the same nutritional benefits. Frequent consumption has already been linked to weight gain and metabolic problems.
The new research doesn’t mean that one soft drink can cause stomach cancer. But it does suggest that continuous daily consumption may be associated with a higher risk in the long run.
Water and other unsweetened beverages can be simple alternatives to sugary soft drinks, sweetened juices, and similar beverages for people in need of a diet to cut back on their consumption.
Stomach cancer has many known and possible risk factors, and diet is only one part of the overall picture. Persistent digestive symptoms, unexplained weight loss, vomiting, difficulty swallowing, blood in the stool, or ongoing stomach discomfort should be discussed with a healthcare professional rather than attributed to diet alone.
The authors emphasized that further studies are needed to confirm the findings. As such, it is yet another reason to consider sugar-sweetened beverages in the daily diet and not expect one sugary drink a day to cause stomach cancer.
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