Stomach cancer is a malignant tumour that starts in cells of the stomach. Malignant means that it is a cancerous tumour that can spread, or metastasize, to other parts of the body.

The stomach is part of the digestive system. It is a muscular, sac-like organ in the upper abdomen. In the stomach, the food is mixed with digestive juices. These juices are made by glands in the lining of the stomach. They help break the food down into a semi-solid mixture that then passes into the small intestine.

Cells in the stomach sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, tumours such as gastric polyps, small gastrointestinal stromal tumours (GISTs) or lipomas.

Changes to cells in the stomach can also cause precancerous conditions. This means that the cells are not yet cancer, but there is a chance that they may become cancer if they aren’t treated. Precancerous conditions that can develop in the stomach are gastric adenoma, or adenomatous polyps, and gastric epithelial dysplasia.

In some cases, changes to stomach cells can cause cancer. Most often, cancer starts in gland cells in the inner layer of the stomach wall, which is called the gastric mucosa. This type of cancer is called adenocarcinoma of the stomach. It makes up about 95% of all stomach cancers.

Symptoms of stomach cancer
Stomach cancer may not cause any signs or symptoms in its early stages because the tumour is small. Also, the abdomen and stomach are large structures that are able to expand, so a tumour can grow without causing symptoms. Symptoms often appear once the tumour grows into surrounding tissues and organs. Other health conditions can cause the same symptoms as stomach cancer. See your doctor if you have these symptoms.

The signs or symptoms of stomach cancer include:
abdominal pain or discomfort (may be vague or mild)
weight loss
fatigue
changes in digestion, including loss of appetite, feeling full after a small meal (early satiety), heartburn (indigestion) or nausea
difficulty swallowing or pain when swallowing
vomiting, with or without blood
anemia
A reduction in the number of healthy red blood cells.
abdominal bloating, especially after eating
blood in the stool
jaundice (the skin and whites of the eyes become yellow and urine is dark yellow)
buildup of fluid in the abdomen (called ascites)
a lump in the abdomen that can be felt during a physical exam

Diet Tips for Fighting Stomach Cancer
#1:  Consume Foods That Contain Quercetin
Diet tip #1: Be sure to include plenty of foods that contain quercetin in your diet. Quercetin is a bioflavonoid that has strong anti-cancer, anti-bacterial, anti-fungal, and anti-inflammatory properties and that is present in high concentration in red and yellow onions. According to one study, half an onion a day could reduce the risk of stomach cancer by 50%. In addition to yellow and red onions, good dietary sources of quercetin include apples, lovage, capers, broccoli, cherries, citrus fruits, red grapes, tea, and many berries, including lingonberries, raspberries, and cranberries.

#2:  Avoid Excess Protein
In 1902, John Beard, a Scottish cancer researcher, discovered that one of the body's primary weapons against cancer is pancreatin. Pancreatin is essentially a mix of protein-digesting enzymes, but these enzymes also have another purpose: the eradication of cancer. Diets that are extremely rich in protein keep the pancreatic enzymes busy digesting protein, and as a result, little time is left for these enzymes to fight stomach cancer. Many nutritionists recommend a protein-free period of approximately 12 hours a day to prevent cancer.
 
#3:  Count on Curcumin
Curcumin is a phytochemical that gives turmeric its intense yellow color. Curcumin has been used, in the form of turmeric, in Ayurvedic and Chinese medicine for centuries due to its medicinal and healing powers. In the recent past, also western scientists have started to pay greater attention to this extraordinary compound which, according to recent studies, has strong anti-cancer properties which make it highly effective against almost any type of cancer, including stomach cancer. One study conducted by University of Chicago researchers showed that curcumin inhibits a cancer-provoking bacteria (H. pylori) associated with stomach cancer. Curcumin has also been shown to trigger apoptosis - a self-destruct mechanism in cancer cells - and to destroy free radicals.

#4:  Avoid Nitrate-Containing Meat Products
Nitrates are substances that naturally occur in our environment. They are present in the air, soil, surface water, and ground water as well as in plants, including vegetables we eat. Nitrates are also used by food manufacturers to give certain meat products an intense red color. When you eat foods that contain nitrates, you body may convert the nitrates into nitrites, which in turn can form nitrosamines. Nitrosamines have been shown to cause certain types of cancer, including stomach cancer. However, nitrosamine formation can be prevented by certain antioxidants, such as vitamin C and vitamin E. As vegetables are typically rich antioxidant vitamins, nitrosamine formation is not considered a concern when you eat vegetables that contain nitrates. This is supported by large-scale population studies that have found no link between a high consumption of nitrate-containing vegetables and cancer, but which show that diets high in nitrate-containing meat products can cause cancer.