ST. PAUL, Minn., March 13 (UPI) -- A study released Thursday found that women who consumed at least one sugar-sweetened beverage daily had a nearly five times greater chance of developing oral cancer than those who largely avoided sugary soft drinks.
The University of Washington study comes as cases of oral cavity cancer are increasing at an "alarming" rate among mainly younger, non-smoking, non-drinking patients without any other identifiable risk factors.
Some have theorized that diet may play a role in the rising numbers.
Oral cavity cancer, for many decades, was primarily associated with older men exposed to well-known cancer risks, including tobacco, alcohol and betel nut chewing. With the advent of anti-smoking health campaigns, the overall number of smoking-related oral cavity cancer cases in Western nations has been steadily declining.
Still, more than 355,000 new cases of oral cavity cancer were diagnosed globally in 2020, with nearly 177,000 deaths.
Most concerning, however, has been an increase in cases among non-smokers globally, especially among younger White women. The cause of this rise remains unknown. Among the possible culprits that have been ruled out is human papillomavirus, or HPV, a common infection spread through sex.
The University of Washington study, published in JAMA Otolaryngology-Head & Neck Surgery, found that high sugary soft drink intake was associated with a significantly increased risk of oral cancer in otherwise low-risk women, regardless of their smoking or drinking habits.
While sugar-sweetened beverages have previously been eyed for links to colorectal and other gastrointestinal cancers, they have never before been studied in connection with cancers of the head and neck.
The results may point the way for a new direction in seeking the cause of oral cancer in low-risk women, according to lead author Dr. Brittany Barber, an assistant professor of otolaryngology head and neck surgery at the University of Washington School of Medicine and her study colleagues.
"Oral cavity cancer is less common than breast or colon cancer, with an annual incidence of approximately 4-4.3 cases per 100,000. However, the incidence of oral cavity cancer is increasing in non-smoking, non-drinking women," Barber said.
"Our study showed that, in women, consuming one or more sugar-sweetened beverage per day was associated with a 4.87 times higher risk of oral cavity cancer or three people more per 100,000 diagnosed.
"Clinicians should be aware of the both the oral health risks associated with consumption of sugary beverages and the emerging oral cavity cancer epidemic in women."
The data was compiled from responses to the national Nurses' Health Study, begun in 1976, and Nurses' Health Study II, begun in 1989, which contain survey information submitted by nearly 163,000 female nurses every two years over the course of three decades on demographics, lifestyle and medical conditions.
From that database of nurses' study participants, the researchers zeroed in on 124 reported cases of invasive oral cavity cancer.
In their models, those nurses who reported drinking one or more sugar-sweetened beverage daily (or five people per 100,000 population) had a 4.87 times higher risk of oral cavity cancer compared with those who drank fewer than one beverage monthly (two per 100,000), increasing the rate of oral cancer by three more people per 100,000 population.
When restricted to both nonsmokers or light smokers and nondrinkers or light drinkers, the risk of oral cancer was 5.46 times higher.
The latest findings build on earlier studies showing that sugary drinks are associated with periodontal disease in young adults, which in turn has been linked with oral cancer.
"Although this association does not imply causality, our hypothesis is that diets with higher added sugar may contribute to chronic inflammation, which may, in turn, contribute to the risk of [oral cavity cancer]," the authors state.
The study is indeed "eye-opening" and addresses "an important question with an elegant study design and generating clear and compelling results," said Dr. Arnaud Bewley, an associate professor who chairs the Department of Otolaryngology at UC-Davis Health.
Bewley, who was not involved in the study, told UPI in emailed comments he is "not surprised that sugary beverages play some role in oral cancer etiology. The high-sugar nature of the modern Western diet is being increasingly understood to be at the root of many chronic diseases, and this study adds to that list.
"As the authors point out, it may not be the sugar itself directly inciting the cancer; It may be the chronic inflammation from dental and gum disease, the alteration in the oral microbiome or even the dental interventions that follow," he said.
Consumption of high sugar beverages also may be associated with other dietary habits or other behaviors that were not captured in the survey and are therefore impossible to control for, he noted.
Agreeing with that assessment was another noted otolaryngologist, Dr. Ilya Likhterov, an associate professor of otolaryngology of the University of California-San Francisco School of Medicine, who told UPI he suspects the consumption of sugary beverages might be a surrogate for a generally compromised and unhealthy "oral biome" in the participants who developed oral cancer.
"We do know that there are young patients who are non-smokers and non-drinkers who don't have the traditional, environmental risk factors for cancer that do develop [oral cavity cancer, and there's been a lot of work being done trying to identify the cause of it," he said.
Regarding sugar-cancer link, "my first thought would be oral hygiene," he added. "We know that patients with gingival disease or chronic inflammation of the mouth have known risk factors for oral cavity cancer.
"Like in the gut, the oral microbiome has 'good' bacteria and 'bad' bacteria. Sugar intake can really change the balance, and that could be a cause for the increase in incidence of oral cavity cancer."
That possibility could be a direction for further research focusing on the effect of changing oral bacteria on the immune system and its ability to fight off mutations, Likhterov said.