How Digestive Health Affects Vitamins and Minerals

Are you getting the nutrients you need?

by Constance Pietrzak, M.D. Health Professional

Various vitamins and minerals are absorbed through the gastrointestinal (GI) tract. Disorders affecting the GI tract may result in deficiencies of these particular vitamins and minerals. Supplementation, therefore, is often needed to ensure that secondary side effects do not occur as a result of these nutritional deficiencies.

Proper absorption of vitamins and minerals requires three steps. First, the gut needs to be able to process the vitamins. Second, vitamins need to be able to cross into the lining of the gut. Finally, the nutrients need to pass into the blood stream in order to be distributed to the proper places in the body. If any of these steps is altered by a disease process in the GI tract, vitamin/mineral deficiencies can result.

Vitamins A, D, E, K

Vitamins A, D, E, and K are known as the fat-soluble vitamins. Anything affecting absorption of fat can reduce the amount of these vitamins absorbed by the body. Fat absorption starts in the mouth and stomach. Eventually, they are processed in the small intestine and absorbed in the last portion of the small intestine called the ileum. Diseases that affect the ileum, particularly Crohn’s disease, celiac disease, or surgical removal of this last part of the small intestine can cause deficiencies in these vitamins.

The more significant effects from deficiencies in the fat-soluble vitamins include:

  • Low vitamin D causes weak bones and osteoporosis. Supplementation is typically delivered via tablets.

  • Low vitamin K can result in bleeding disorders and excessive bleeding.

  • Low vitamin A causes night blindness.

Vitamin B12

Vitamin B12 is absorbed in the ileum, as well. Any disease affecting the last portion of the small intestine will also cause deficiencies in vitamin B12. Low vitamin B12 can result in anemia and major neurological problems. Supplementation is given in pill form, but more severe deficiencies often require monthly injections of B12.


Iron is absorbed in the first portion of the small intestine, the duodenum. Gastrointestinal disorders that can affect this part of the small intestine include Crohn’s disease and celiac disease.Iron deficiency causes anemia, which can become severe. Sometimes blood transfusions may be required. Those with iron deficiency need to undergo extensive GI testing, gynecologic testing (in women), and hematologic testing to ensure no major medical issue is causing the iron deficiency. Once diagnosed, supplementation is typically with tablets; however, iron infusions are sometimes needed on a regular basis to ensure adequate iron stores in the body.


The number of surgeries performed in order to help correct obesity continues to rise significantly, and various procedures are performed to help with weight loss. Particular surgeries, namely the Roux-en-y gastric bypass surgery and the sleeve gastrectomy, can result in malabsorption of some vitamins and minerals since the anatomy of the gastrointestinal tract is altered after surgery. Lifelong supplementation of vitamins and minerals is crucial to prevent deficiencies.

Those with severe Crohn’s disease that does not respond to medical treatment may require removal of parts of the small intestine affected by Crohn’s. If the parts of the small intestine that absorb nutrients are removed, nutritional deficiencies can occur.

Proper intake of vitamins and minerals is only one step in maintaining adequate nutrition. An intact gut lining is necessary in order to complete the process of absorbing vitamins and minerals. Any disorders of the GI tract lining can cause abnormalities in vitamin and mineral levels, so blood levels should be checked periodically in order to ensure proper nutrition. Be sure to talk to your doctor if you have any concerns about your vitamin and mineral levels.

Constance Pietrzak, M.D.
Meet Our Writer
Constance Pietrzak, M.D.

Constance Pietrzak, M.S., M.D., is a gastroenterologist with Advocate Medical Group in Chicago. Through her work with HealthCentral, she strives to expand knowledge on gastroesophageal reflux disease (GERD) and inflammatory bowel disease (IBD). Follow Constance on Twitter for timely updates on IBD, and more.