High sugar and salt are primary causes for stomach cancer risk in unhealthy diets, scientists warn

A new study of Brazilian diets pinpoints sugar added to food as the “villain” in the relationship between stomach cancer and an unhealthy diet, while salt was found to increase the risk of tumors in people with habits considered healthy.

The study identified an unhealthy dietary pattern as one high in processed meats, carbonated drinks high in sugar, and fast food. Conversely, healthy patterns were outlined as diets high in fruits and vegetables and low sodium.

“The population lacks information about food. It’s not about terrorism; it’s about popularizing the subject, explaining more about diets, teaching health workers, talking about it in health centers,” urges oncologist Maria Paula Curado, head of the Cancer Epidemiology and Statistics Group at the International Research Center of the A.C.Camargo Cancer Center.

“We need to create a philosophy that educates, informs, and respects the culture of each region. There’s no point in telling someone who eats barbecue every day that they can’t eat it anymore because they’re going to die of cancer. It’s not like that. You have to inform them about the risks.”

The study was published in the scientific journal BMC Medicine.

Looking deeper into regional diets

Most studies on diet and cancer look at individual foods, like “does eating broccoli prevent cancer?” This study took a different approach, as its researchers wanted to understand how overall eating patterns, not just single foods, affected stomach cancer risk.

The study analyzed data from a large sample of individuals from four state capitals in different regions of Brazil. In total, the analysis involved 1,751 participants from São Paulo, Goiânia, Fortaleza, and Belém, the latter having the highest rates of the disease.

The researchers asked participants about their diets using a 130-item questionnaire, then used a statistical technique to find common eating patterns.

Added sugars introduced in processed foods contribute between 7–21% to an increased risk of gastric cancer.

Finally, the researchers used mediation analysis to see if these patterns directly caused cancer.

“Each region and culture in Brazil has its own behavior. The eating habits of people in Belém are not the same as those in Goiânia or São Paulo, but they can lead to the same disease,” explains Curado.

“We decided to do a case control study, meaning that for each patient, we looked for another person without the disease in the same region. We also included a group who had undergone endoscopy and did not have cancer.”

“This was time-consuming, but we obtained an important result that contributes to elucidating the mechanisms involved in gastric cancer from an epidemiological perspective, with implications for public health.”

Salt’s role in gastric cancer

The scientists found that added sugars introduced in processed foods contribute between 7–21% to an increased risk of gastric cancer.

The study strongly suggests sodium is a risk factor that directly influences carcinogenesis. However, other things in a typical “healthy diet,” like consuming less saturated fat or more fiber, don’t seem to have an impact on lowering risk.

Additionally, an excessive intake of salt has harmful effects on the gastric mucosa, leading to inflammation and interactions with colonization by Helicobacter pylori, a bacterium commonly found in the stomach but which can cause gastritis.

“Increased sodium intake can induce atrophic gastritis and metaplasia, complications resulting from chronic irritation of the gastric mucosa, leading to cancer,” the researchers claim.

The WHO recommends that sodium intake should be less than 2 g per day, the equivalent of five small teaspoons of salt. Brazilians consume nearly double the daily sodium recommendation.

For added sugar, the maximum consumption should be 10% of daily calories. For example, on a 2,000-calorie diet, this percentage equals 50 g of sugar per day, or up to ten teaspoons.

Most Brazilians over-consume salt

Stomach cancer is the sixth most common cancer in Brazil, with an estimated 21,000 new cases in the three-year period 2023–2025, according to the country’s National Cancer Institute.

It also has a high mortality rate — 75% of patients die within five years.

A recent national food survey estimated that approximately 60% of the adult Brazilian population exceeds the recommended sodium limits, mainly due to the consumption of white bread, toast, beans, rice, and beef.

Products labeled as “whole grain,” including breakfast cereals, breads, and cookies, can also contain high levels of sodium.

In the study, the researchers point out that Brazil implemented new food labeling laws in 2022 to improve understanding of nutritional information to help consumers make informed choices.

The labeling rules require the display of a magnifying glass symbol indicating one or more nutrients if products contain, for example, 600 mg or more of sodium per 100 g of solid food or 15 g or more of added sugar per 100 g.

Previous cancer research has suggested that sugar-sweetened beverages may boost the probability of developing colorectal cancer among women under 50. Meanwhile, an Australia study suggested that changing the recipes of packaged foods to reduce sodium could save “1,770 lives per year in the country” and prevent “nearly 7,000 annual diagnosis of heart disease, kidney disease and stomach cancer.”