Researchers employed a novel approach to analyze data from a large sample of residents across four state capitals in different regions of Brazil, contributing to the development of preventive strategies for this type of tumor.

Sugar added to food may be the “villain” in the relationship between stomach cancer and an unhealthy diet, while salt increases the risk of tumors even in individuals with otherwise healthy eating habits. This conclusion comes from a study conducted in Brazil and published in the scientific journal BMC Medicine.

The study defined an unhealthy dietary pattern (UDP) as one characterized by a high consumption of processed meats, sugary carbonated drinks, and fast food. In contrast, a healthy dietary pattern (HDP) was identified by a high intake of vegetables and fruit, along with low sodium levels.

The researchers found that the UDP is associated with an increased risk of gastric cancer, with added sugars—introduced during food processing to enhance sweetness—contributing between 7% and 21% to this association. Sodium intake was identified as the primary mediating factor linking the HDP to the risk of gastric adenocarcinoma. No mediating effects were observed for saturated fatty acids or 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: A Deadly Cancer

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.

Reference: “Exploring the link between dietary patterns and gastric adenocarcinoma in Brazil: a mediation analysis” by Alex Richard Costa Silva, Gianfranco Alicandro, Valdete Regina Guandalini, Patrícia Paula da Fonseca Grili, Paulo Pimentel Assumpção, Mônica Santiago Barbosa, Rosane Oliveira de Sant’Ana, Felipe José Fernández Coimbra and Maria Paula Curado, 28 November 2024, BMC Medicine.
DOI: 10.1186/s12916-024-03785-2

The study was funded by the São Paulo Research Foundation.