Gastric, or stomach, cancer kills about 800,000 people per year worldwide, according to the World Health Organization. It is more common in those who eat smoked foods, have certain stomach infections, and/or use tobacco and alcohol. One potential treatment for gastric cancer is gastrectomy, which is removal of the stomach. If the cancer has not spread beyond the tissues of the stomach, gastrectomy might be curative by removing the source of the cancer. However, the procedure has several effects on the body, including changing the digestion of vitamin B12.
Surgery and Gastric Cancer
Surgery is a common treatment for gastric cancer. The extent of surgery depends on the extent of the tumor, how large it is, how far it has spread and the location. It might involve removing a part of the stomach or the entire stomach and surrounding lymph nodes. Removing the entire stomach is called a gastrectomy. The outcome might be curative, or may at least relieve some symptoms.
Vitamin B12 Function
Vitamin B12 helps the cells of the body perform chemical reactions. It is important for DNA synthesis and maintenance. An absence of vitamin B12 will lead to the condition called pernicious anemia, which creates low red blood cell counts and nerve problems. Symptoms might include fatigue, weakness, pain and loss of sensation in the limbs.
Vitamin B12 Absorption
Normal vitamin B12 absorption requires the stomach. Gastrectomy for gastric cancer will prevent absorption of vitamin B12. This is because special cells in the stomach release a protein called intrinsic factor, which binds to vitamin B12 in the intestine and allows it to be absorbed into the bloodstream.
Treatment of B12 Deficiency
Because vitamin B12 cannot be absorbed in the digestive system after the stomach is removed, oral B12 supplements are of no use. Typically, B12 is given by injection intramuscularly, where it can slowly enter the bloodstream and be taken into the cells.
References
- World Health Organization: Cancer
- "Harrison's Principles of Internal Medicine (17th edition)"; Dr. Anthony Fauci et al; 2008
- "Sabiston Textbook of Surgery (18th edition)"; Dr. Courtney Townsend et al; 2007
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