Overview

Cancer occurring in the gastrointestinal (GI) tract affects vital organs, such as the stomach, colon, and anus, which play essential roles in the digestion, absorption and excretion of our food. More specifically, stomach (gastric) cancer has been ranked by Cancer Research UK as the eighteenth most commonly diagnosed cancer. While it may not rank among the most frequently diagnosed, its impact is severe, especially when looking at survival rates.¹

Survival statistics of stomach cancer

In cancer statistics, the five-year survival rate is often used as a key measure, representing the percentage of patients who survive at least five years after their diagnosis or the start of treatment. For stomach cancer patients, the five-year survival rate ranged from 0% to 50%, depending on the stage and severity of the disease.²

• Patients diagnosed at an early stage, where cancer remains localised and can be surgically removed, have a five-year survival rate of up to 50%
• For those with metastatic stomach cancer, where the disease has spread to distant organs, the five-year survival rate is nearly 0%

This drastic contrast shows the importance of early detection and interventions in improving patient outcomes. To understand why stomach cancer can be detrimental, it is important to first review its vital role in maintaining overall health. 

What is the purpose of the stomach? 

The stomach is a complex organ that plays a central role in the digestive process while also performing important protective functions. Its key roles include the following:³

1. Mechanical and chemical digestion: once partially digested food from the mouth enters the stomach, it undergoes further breakdown through a combination of muscular contractions and enzymatic activity. The stomach’s rhythmic contractions create a churning motion that mixes the food with gastric juice that is released by the stomach, including hydrochloric acid (HCl) and the enzyme pepsin. This process is essential for converting food into a semi-liquid form (chyme) that can pass smoothly into the small intestine for nutrient absorption
2. Protein breakdown: HCl creates a highly acidic environment, which is necessary for the enzyme pepsin to work effectively. Pepsin is an enzyme that breaks down complex protein structures into smaller molecules, making them easier to absorb
3. Defence against pathogens: the stomach’s acidity also serves a protective function by neutralising or killing harmful microorganisms (pathogens) that may enter the body through ingested food, acting as a first line of immune defence
4. Mucosal protection: The harsh acidic environment created by the release of HCl can damage the stomach tissue. The stomach protects itself from damage by producing a thick mucus layer that coats the inner lining

Collectively, these functions highlight the complexity of the stomach, as it is required not only for digestion but also for the maintenance of GI health and protection of the body from external threats. Therefore, it is essential to protect and preserve the health of this vital organ. 

One key factor influencing stomach health is nutrition, which plays a significant role in both the initiation and progression of stomach cancer. By educating ourselves on how specific dietary choices impact cancer risk, we can take proactive steps toward better health. In this article, we will be exploring the following: 

• How certain types of foods and habits contribute to stomach cancer
• Digestive challenges faced by individuals during illness and treatment
• The types of foods that can support optimal nutrition during and after treatment

Causes of stomach cancer: how can diet contribute to stomach cancer? 

Risk factors 

Cancer is a disease caused by genetic mutations (errors in the DNA) that disrupt the normal regulation of cell growth and division. These mutations can cause cells to multiply uncontrollably, leading to the formation of tumours. In the case of stomach cancer, several risk factors are known to contribute to its development. These include infection with Helicobacter pylori (H. pylori), dietary habits, genetics, and age. Understanding these risk factors is key to the prevention, early detection, and effective management of stomach cancer.^2,4

Helicobacter pylori (H. pylori)

H. pylori is a type of bacteria that commonly infects the stomach and is recognised as the primary risk factor for gastric cancer. It can be transmitted directly from person to person or indirectly through ingesting food or water contaminated with an infected person’s saliva, vomit, or stool. One of the major challenges with H. pylori infection is that it is often asymptomatic, meaning many individuals do not experience any noticeable symptoms. As a result, the infection can go undetected for years, leading to chronic inflammation of the stomach lining. 

Reactive substances are released from activated immune cells attempting to eradicate the bacteria and from H. pylori itself as it attempts to infect host cells. This creates a toxic cellular environment that promotes DNA damage in the cells lining the stomach. Additionally, this bacterium can impair the cells’ natural DNA repair mechanisms. The combination of the ongoing DNA damage and compromised repair process promotes the accumulation of genetic mutations, which increases the risk of gastric cancer.⁵

Dietary habits and food choices

Several types of food and dietary habits have been associated with stomach cancer due to their potential to promote inflammation, damage the stomach lining, or contribute to carcinogenic processes. Examples include:

• Alcohol: the exact mechanism is not fully understood; moderate and heavy alcohol drinking has been associated with an increased risk of stomach cancer⁶ 
• Excess salt: ​​foods high in salt, such as processed meats, anchovies, and certain cheeses, can be detrimental to health when consumed regularly in large quantities. This is because excessive salt intake can damage the protective lining of the stomach, increasing the likelihood of genetic mutations over time. Additionally, this damage allows H. pylori to infect the stomach more easily and promotes chronic inflammation, which are known risk factors for the development of stomach cancer⁷ 
• High-fat diets: diets rich in saturated fats, which include the frequent consumption of red meat or processed meats, can induce chronic inflammation and obesity, both of which are linked to higher cancer risk⁸
• Smoked or cured foods: often contain polycyclic aromatic hydrocarbons (PAHS), carcinogenic compounds. Carcinogens typically facilitate cancer development by inducing DNA damage that leads to the accumulation of genetic mutations. PAHS do this indirectly by stimulating the production of DNA-damaging molecules, such as reactive oxygen species (ROS)⁹ 
• Low-vitamin A and C diet: adequate intake of vitamins A and C is important, as both are antioxidants associated with a reduced risk of gastric cancer. It plays a significant role in the diet, as low intake has been consistently linked to an increased risk of cancer development^10,11 

Being aware of these dietary risk factors can help guide healthier food choices, reducing the likelihood of stomach cancer development.

Genetics 

Genetic syndromes, such as juvenile polyposis syndrome (JPS) and Peutz-Jeghers syndrome (PJS), have been linked to an increased risk of developing stomach cancer. This is because they are characterised by the formation of polyps (non-cancerous abnormal growths) in the GI tract. While polyps are benign, their presence over time significantly elevates the risk of malignant transformation that can become cancerous over time. Because of this, people with these syndromes are monitored closely, and polyps are often removed to prevent complications.^2,12

Ageing 

As we age, increased levels of inflammation and a decline in immune function commonly occur. This creates a cellular environment more susceptible to DNA damage and reduces the body’s ability to detect and eliminate abnormal cells. As a result, there is a heightened risk of accumulating genetic mutations, which can lead to uncontrolled cell division and, ultimately, the development of cancer.¹³

Digestive challenges in stomach cancer 

Stomach cancer can compromise the digestive process due to the effects of both the disease itself and the treatments used to manage it, such as surgery, chemotherapy and radiation. As the stomach plays a central role in breaking down food and regulating its passage to the intestines, any disruption to its structure or function can lead to digestive challenges. For example, when a small or large amount of the stomach is surgically removed (a procedure called a gastrectomy), patients may experience symptoms such as poor appetite, unintended weight loss, heartburn, abdominal pain, fatigue and anaemia (due to poor iron absorption).^14,15 These changes often require dietary modifications to help manage symptoms and ensure adequate nutrition.

Recommended dietary strategies

For individuals with stomach cancer, adopting appropriate dietary strategies is essential to support overall health, manage symptoms, and improve treatment outcomes. Key strategies include:

• Following a gastrectomy (the removal of all or part of the stomach), it is recommended to consume small, frequent meals throughout the day and to limit the intake of simple carbohydrates, such as sweets and fizzy drinks. This helps reduce the risk of dumping syndrome, a common post-surgical complication that occurs when food moves too quickly from the stomach into the small intestine. Dumping syndrome can trigger a range of unpleasant symptoms, including abdominal pain, nausea, diarrhoea, dizziness, and low blood glucose levels^15,16 
• Patients undergoing cancer therapy are recommended to have a high-protein diet to minimise weight loss, support recovery, prevent muscle loss, and improve muscle strength. This is particularly important as it can support physical function, enhancing overall quality of life, and reduce the likelihood of treatment-related complications. Good sources include lean meats, fish, eggs, dairy, legumes and tofu¹⁷ 
• If a patient is unable to consume food orally or absorb nutrients due to the effects of treatment or the tumour itself, artificial nutrition may be necessary. This involves providing essential nutrients through a feeding tube, which is inserted either into the stomach or intestines (enteral nutrition) or directly into the bloodstream via a vein (parenteral nutrition)^18,19
• Depending on the type of surgery or treatment, patients may need additional vitamins such as B12, iron, calcium, or vitamin D, particularly if absorption is affected

Summary

Stomach cancer is influenced by a range of factors, including genetics, H. pylori infection, age, and particularly diet. Diets high in processed, salty, and smoked foods, as well as excessive alcohol consumption, are associated with increased cancer risk. On the other hand, adopting dietary strategies such as consuming small, frequent meals and prioritising a protein-rich diet can help manage symptoms and support recovery during treatment.

By learning more about the links between nutrition and stomach cancer, individuals can make informed choices that support prevention, improve outcomes, and enhance overall well-being. Whether through small dietary changes, increased awareness, or support during treatment, nutrition remains a powerful tool in managing this disease.