Added sugar and salt are the ‘villains’ in the relationship between dietary patterns and stomach cancer

 Sugar added to food may be the “villain” when it comes to the relationship between stomach cancer and an unhealthy diet, while salt increases the risk of tumors in people with habits considered healthy. This is the result of a study carried out in Brazil and published in the scientific journal BMC Medicine.

The study considered an unhealthy dietary pattern (UDP) to be one that included high consumption of processed meats, carbonated drinks high in sugar, and fast food. On the other hand, the healthy pattern (HDP) was characterized by a high intake of vegetables, fruit and low levels of sodium.

The scientists concluded that the UDP is associated with an increased risk of gastric cancer, with added sugars – introduced during processing to sweeten foods – contributing between 7% and 21% to this ratio. Sodium intake is the main mediating factor in the association between the healthy pattern and the risk of gastric adenocarcinoma. No mediating effects were found for saturated fatty acids and fiber.

Using an innovative approach, the study analyzed data from a large sample of individuals from four state capitals in different regions of Brazil. It involved 1,751 participants, including patients and controls, from São Paulo, Goiânia, Fortaleza and Belém, the latter having the highest rates of the disease.

Gastric adenocarcinoma is a malignant tumor that develops in the innermost layer (mucosa) of the stomach and accounts for more than 90% of cases of this type. 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 National Cancer Institute (INCA). It also has a high mortality rate – 75% of patients die within five years.

In the multicenter case-control study, consumption patterns were identified by exploratory factor analysis (a statistical technique that identifies patterns and relationships underlying a set of variables) using a 130-item food frequency questionnaire adapted for each region of the country. To disentangle the direct and indirect effects of these patterns on gastric cancer risk, the researchers performed a mediation analysis.

The conventional approach in the scientific literature dealing with the relationship between diet and cancer has focused on individual foods or nutrients, ignoring a broader perspective of dietary patterns, as was adopted in this study.

“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. 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,” oncologist Maria Paula Curado, head of the Cancer Epidemiology and Statistics Group at the International Research Center of the A.C.Camargo Cancer Center, told Agência FAPESP.

Corresponding author and supervisor of the first author of the article – doctoral student in oncology and nutritionist Alex Richard Costa Silva – Curado was supported by FAPESP through the Thematic Project “Epidemiology and Genomics of Gastric Adenocarcinomas in Brazil”. In addition, the research had the international collaboration of researcher Gianfranco Alicandro, professor at the University of Milan (Italy).

“This study is part of my doctoral thesis and provides new perspectives on the relationship between diet and gastric adenocarcinoma. We highlight that the role of added sugars is still little explored in the literature on diet and gastric cancer, which provides new insights for future research,” adds Silva.

The relationship

Sodium is a risk factor that directly influences carcinogenesis. Excessive intake 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, for example. Increased sodium intake can induce atrophic gastritis and metaplasia, complications resulting from chronic irritation of the gastric mucosa, leading to cancer.

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.

“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. 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. What we’re trying to do is prevent, diagnose early, and teach healthy eating in a practical and realistic way,” adds Curado, who has been included in the Stanford/Elsevier University list of the world’s top 2% of scientists since 2020.

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 milligrams (mg) or more of sodium per 100 grams of solid food or 15 grams or more of added sugar per 100 grams.

The World Health Organization (WHO) recommends that sodium intake should be less than 2 grams 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 grams of sugar per day, or up to ten teaspoons. A 350 ml carton of soft drinks has an average of 38 grams of added sugar.

In the research, the scientists suggest implementing additional initiatives and strategies for healthier food choices aimed at reducing sodium and added sugar intake to prevent gastric cancer.

About FAPESP

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the state of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration.