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Throughout the semester, we learned about the four main functions of the digestive system. That includes taking in food, breaking it down into nutrient molecules, absorbing molecules into the bloodstream, and ridding the body of any indigestible remains. We also learned the six steps that support these processes- ingestion, propulsion, mechanical breakdown, digestion, absorption, and defecation. For my STEAM project, I decided to research what happens when someone goes through a gastrectomy and how they are still able to absorb vitamin B12, an essential nutrient needed for red blood cell production, nerve function, and DNA synthesis.
The media I chose for this project is a pamphlet, so that I could clearly and visually represent the digestive process and the changes that are made when the stomach is surgically removed. This topic directly connects with our course objective by describing the full digestive process and what happens when a step, specifically involving the stomach, is disrupted.
Vitamin B12, also known as cobalamin, is a water-soluble vitamin that is essential for nervous system function, red blood cell development, DNA synthesis, energy metabolism, and antioxidant activity. It is normally obtained from an animal-based diet (Wolffenbuttel et al., 2024). In a normal digestive process in the stomach, hydrochloric acid helps release B12 from food, and the food carrier proteins let the B12 bind to haptocorrin. In the duodenum, pancreatic enzymes break down haptocorrin which allows the pH change to trigger the transfer of B12 to the intrinsic factor (IF) which is a protein made by the stomach. Cubilin and amnionless are the 2 components of the receptor that B12 binds with when it goes up the distal ileum. B12 after absorption in the bloodstream then binds to transcobalamin (TC) for systemic transport. Some of the B12 from the liver is excreted in the bile and reabsorbed in the intestines through a process known as enterohepatic circulation (Shibboleth Authentication Request, n.d.).
When a person has a gastrectomy, the surgical removal of the stomach involves the process being disrupted. Intrinsic factor is only made in the stomach and after a gastrectomy there is little to no more of it or gastric acid, and the active mechanism in the body where B12 is absorbed is either less available or not available at all depending on if the surgery was a total or a part of a gastrectomy. This can lead to B12 deficiency, which can cause many symptoms such as numbness, weakness, abnormal gait, memory loss, depression, and anemia among many others (No Stomach for Cancer, 2023). Studies have even shown that up to 49% of patients who have a gastrectomy develop B12 deficiency. This condition, known as pernicious anemia, happens when red blood cells can’t mature properly due to lack of B12.
After a gastrectomy, people must rely on other ways to absorb B12. The most effective treatment is vitamin B12 injections, which bypass the digestive system completely and go straight into the bloodstream. These are typically intramuscular injections starting with high doses weekly, then switching to monthly 1,000 mcg doses for the rest of a patient’s life (No Stomach for Cancer, 2023). Another treatment is oral supplementation with 1,000–2,000 mcg tablets daily, which has been shown to be just as effective once levels are baseline. There are also under the tongue and intranasal methods that can be used once B12 levels are normalized.
Along with supplementation, lifestyle and dietary changes are equally as important. Patients are often advised to eat small, frequent meals throughout the day because of changes in digestion and absorption after gastrectomy. Frequent monitoring of B12 levels is also very important for patients experiencing B12 deficiency.
Work Cited:
Bahardoust, M., Aghakhani, Z., Mousavi, S., Donyadideh, G., Ziafati, H., Alipour, H., Haghmoradi, M., Olamaeian, F., Tayebi, A., & Tizmaghz, A. (2023). Vitamin B12 deficiency after total gastrectomy for gastric cancer, prevalence, and symptoms: a systematic review and meta-analysis. European Journal of Cancer Prevention, 33(3), 208–216. https://doi.org/10.1097/cej.0000000000000838
Halsted, J. A., Gasster, M., & Drenick, E. J. (1954). Absorption of Radioactive Vitamin B12 after Total Gastrectomy. New England Journal of Medicine, 251(5), 161–168. https://doi.org/10.1056/nejm195407292510501
No Stomach for Cancer. (2023, March 24). Nutrient deficiencies — No stomach for cancer. https://nostomachforcancer.org/after-diagnosis/life-without-a-stomach/special-concerns/nutrient-deficiencies/
Perrine, S. (2023, July 18). Why you might need more B12 and D3 vitamins. AARP. https://www.aarp.org/health/drugs-supplements/vitamin-b12-d3/?cmp=RSKJMQLDHK&gclid=7c81d53ca7911461eab1bd3d818fb4af&gclsrc=3p.ds&msclkid=7c81d53ca7911461eab1bd3d818fb4af&utm_source=bing&utm_medium=cpc&utm_campaign=Health-Supplements-NonBrand-Phrase&utm_term=what%20is%20vitamin%20b12&utm_content=HealthyLiving-Vitamin%20B12
Shibboleth Authentication Request. (n.d.-a). https://www-sciencedirect-com.uaf.idm.oclc.org/science/article/abs/pii/S0083672922000164?via%3Dihub
Shibboleth Authentication Request. (n.d.-b). https://research-ebsco-com.uaf.idm.oclc.org/c/u4if57/search/details/is43zfwa7b?db=aph%2Cagr%2Cawh%2Cant%2Casf%2Cbai%2Cndh%2Cbft%2Cbuh%2Cufh%2Ccph%2Ceft%2Ceric%2Cegi%2Chev%2Cffw%2Czbh%2Cgft%2C8gh%2Chxh%2Chch%2Ckhh%2Chft%2Clft%2Clxh%2Culh%2Clth%2Ccmedm%2Cmih%2Cmth%2Ckah%2Cmzh%2Cn5h%2Cofm%2Ce865sww&isDashboardExpanded=true&limiters=RV%3AY&q=gastrectomy%20b12%20absorption
Vitamin B12 deficiency. (2025, March 19). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/22831-vitamin-b12-deficiencyWolffenbuttel, B. H. R., McCaddon, A., Ahmadi, K. R., & Green, R. (2024). A brief overview of the diagnosis and treatment of cobalamin (B12) deficiency. Food and Nutrition Bulletin, 45(1_suppl), S40–S49. https://doi.org/10.1177/03795721241229500
In Aria’s project the topic is the absorption of vitamin b12, and how it works after a gastrectomy. This relates to the objective of the 4 functions of the digestive system, which includes absorption as the third step. Intrinsic factor is produced in the stomach which is vital for the absorption of B-12. B12 is first broken down in the stomach by HCl and bound to Haptocorrin. This intrinsic factor then replaced Haptocorrin in the Duodenum. As it reaches the Ilium it joins with a receptor that is made up of Cubilin and Amnionless.The B12 is then absorbed, and once inside the bloodstream it is bound to and transported by transcobalamin.
Without the stomach to produce intrinsic factor the B12 cannot be absorbed, leading to about half of patients who undergo the procedure becoming ill and having symptoms such as weakness and anemia. This is because B12 is necessary for the growth and maturation of red blood cells. The replacement for this is either through an injection which means the body does not need to absorb it and it is instead directly entering the bloodstream, or through supplement pills. These supplement pills are daily high doses, about 1-2 thousand mcg, while the shots are first high dose weekly, then 1000 mcg monthly.