What causes stomach cancer

Overview

Stomach cancer, also known as gastric cancer, is a disease in which malignant (cancerous) cells form in the lining of the stomach. While the exact cause is complex and multifactorial, a combination of genetic predisposition and environmental factors plays a significant role. Understanding these causes is crucial for prevention and early detection efforts.

Key Causes and Risk Factors

1. Helicobacter pylori (H. pylori) Infection

The most significant and widespread cause of stomach cancer globally is infection with the bacterium Helicobacter pylori. This bacterium colonizes the stomach lining and can cause chronic inflammation (gastritis). Over many years, this inflammation can lead to precancerous changes in the stomach lining, such as atrophic gastritis and intestinal metaplasia, which significantly increase the risk of developing adenocarcinoma, the most common type of stomach cancer.

H. pylori is thought to spread through contaminated food and water and is more common in areas with poor sanitation. It is estimated that H. pylori infection is responsible for about 60% of all stomach cancers worldwide.

2. Diet and Lifestyle

Dietary habits and lifestyle choices are major contributors to stomach cancer risk:

• Diet High in Salted, Smoked, and Pickled Foods: Consuming large amounts of these foods, common in some traditional diets, is strongly associated with an increased risk. The high salt content may damage the stomach lining, and the processes used to preserve these foods can create carcinogenic compounds (like N-nitroso compounds). Studies suggest this dietary pattern can increase risk by up to 11 times compared to diets low in these foods.
• Diet Low in Fruits and Vegetables: Conversely, a diet rich in fresh fruits and vegetables, which contain antioxidants like vitamins C and E, may protect against stomach cancer. These nutrients can help repair cellular damage and inhibit the formation of cancer-causing substances.
• Smoking: Tobacco smoking is a well-established risk factor for many cancers, including stomach cancer. Smokers have approximately double the risk of developing stomach cancer compared to non-smokers. The chemicals in tobacco smoke can damage DNA and contribute to the development of cancer.
• Obesity: Being overweight or obese is linked to an increased risk of several types of cancer, including stomach cancer. The exact mechanisms are still being researched but may involve hormonal changes, chronic inflammation, and increased levels of certain growth factors associated with excess body fat. Obesity can increase the risk by 20-30%.
• Alcohol Consumption: While the link between alcohol and stomach cancer is less strong than for some other cancers, heavy alcohol consumption may slightly increase the risk.

3. Age and Gender

Stomach cancer is more common in older adults, with most cases diagnosed in people over the age of 60. Men are also more likely to develop stomach cancer than women.

4. Family History and Genetics

Having a first-degree relative (parent, sibling, or child) with stomach cancer increases an individual's risk. This increased risk can be due to shared environmental exposures or inherited genetic factors.

• Inherited Syndromes: While most stomach cancers are sporadic (occur by chance), a small percentage (around 1-2%) are strongly linked to inherited genetic mutations. These include hereditary diffuse gastric cancer (CDH1 gene mutation), Lynch syndrome (hereditary non-polyposis colorectal cancer), and familial adenomatous polyposis (FAP). Genetic counseling and testing may be recommended for individuals with a strong family history.

5. Other Medical Conditions

Certain medical conditions can increase the risk of stomach cancer:

• Pernicious Anemia: This condition involves a lack of intrinsic factor, which is needed to absorb vitamin B12. Chronic gastritis associated with pernicious anemia can increase stomach cancer risk.
• Chronic Gastritis: Long-term inflammation of the stomach lining, often caused by H. pylori or autoimmune conditions, can predispose individuals to cancer.
• Epstein-Barr Virus (EBV) Infection: A small percentage of stomach cancers are associated with EBV infection, though the role of EBV is not fully understood.
• Previous Stomach Surgery: Individuals who have had part of their stomach removed (gastric surgery) for non-cancerous conditions, such as ulcers, may have a slightly increased risk of developing cancer in the remaining stomach tissue years later.

6. Environmental Factors

Exposure to certain environmental agents, such as dust, fumes, and specific chemicals encountered in some occupations, has been suggested as a possible risk factor, although the evidence is not always conclusive.

Conclusion

Stomach cancer arises from a complex interplay of factors, with H. pylori infection and dietary habits being the most prominent. While some risk factors like age and genetics cannot be changed, adopting a healthy lifestyle—including a balanced diet rich in fruits and vegetables, avoiding smoking, maintaining a healthy weight, and practicing good hygiene to prevent H. pylori infection—can significantly reduce the risk.