The Importance of Micronutrient Supplementation Post-Bariatric Surgery

January 05, 2018 (Fri)

Post-surgery patients focus on supplemental calcium, vitamin D, iron and the Vitamin B-complex as it is crucial in preventing malnutrition/absorption conditions such as scurvy, beri beri, anemia, rickets or pellagra. For patients, what is important to understand is that pre-surgery ingestion of supplemental micronutrients (i.e taking a multivitamin) is about “additional nutrition to usual diet”, but post-surgery is about “replacement of those nutrients with supplements that would have normally been delivered via food.” 1,2,3


Digestion begins in the mouth with mastication of foodstuffs where linear starches (and minimal fats) are partially digested before entering the stomach. This bolus is typically broken into 1 mm sized particles that are then mixed with an amalgam of enzymes and acids for further digestion into chyme. Within 1 – 4 hours the contents of the stomach typically empty, beginning with liquids, moving on to carbohydrates then proteins, fats and lastly fiber containing foods. Under normal digestion conditions (i.e. no surgery), the vast majority of nutrition is digested and absorbed via the duodenum and proximal jejunum (92-97%). Once chyme passes on to the mid-jejunum, nutrient absorption is essentially complete, with only a few tasks remaining: micronutrient absorption being one. 4, 5


Micronutrients (minerals, vitamins and trace elements) and any remaining luminal fluids are all absorbed before reaching the colon – that means between the mid-jejunum and the colon (passing through the ileum) the balance of nutrient absorption takes place. Most vitamins enter the blood stream via a process called passive absorption. Mineral absorption is more complicated and occurs in several stages and requires energy to be absorbed, also known as active transport. But, in the case of bariatric surgery, aspects of normal digestion are changed, interrupted or mechanically altered. This has an effect on nutrient absorption since surgery increases competition for the body’s ability to absorb.5


Post-bariatric surgery patients will be consuming less calories and as a result less micronutrients from food. In the case of the Roux-En-Y procedure patients will not absorb nutrients which will lead to malnutrition. Therefore, after any bariatric surgery, taking supplemental micronutrients will become a way of life otherwise patients risk malnutrition. In fact, the American Society for Metabolic & Bariatric Surgery (ASMBS) has published very specific guidelines for doctors to follow that guide patients on the correct post-operative supplement program.6


Current minimum recommendations state that patients must take a daily multivitamin (two per day and must contain iron, folic acid and thiamine), 1200 – 1500 mg of elemental calcium (in diet and as citrated supplement in a divided dose over the day), minimum 3000 IU vitamin D, vitamin B12 (sublingual) as needed to maintain proper nutritional status (checked by doctor), and  iron (both in diet at 45 – 60 mg and as supplemental).6 The below table summarizes supplements, recommended dosage and suggested dosing times:    


Frequency and Dosing Table



Dosing Time

Dosage & Notes


Before Bed

(Basic – nothing for “seniors,” “women,” “men” or gummies)


3 times per day

1200 – 1500 mg as Calcium Citrate separated into 500 – 600 mg doses.  

Vitamin D

With Calcium

3000 IU per day, or as recommended by physician; take with calcium

Vitamin B12

Once per week

Sublingual; take one weekly dose or as recommended by physician



Take on empty stomach and not with calcium by at least 2 hours; see physician for specific dose and needs


While bariatric procedures have different post-operative nutritional requirements for patients, what is abundantly clear is that supplementation is necessary to obtain optimal patient health. Patients must be made aware of the implications of the surgery and the necessary life-changes that will be needed post-surgery. Patients will need consults with appropriate medical teams such as registered dietitians or nurse practitioners to help develop an implementable and manageable plan.  



  1. Sawaya, RA et al. Vitamin, Mineral and Drug Absorption Following Bariatric Surgery. Curr Drug Metab. 2012 November; 13(9):1345-1355.
  2. Xanthakos SA. Nutritional deficiencies in obesity and after bariatric surgery. Pediatr Clin North Am. 2009; 56:1105–1121.
  3. Livingston EH. The incidence of bariatric surgery has plateaued in the U. S Am J Surg. 2010; 200:378–385.
  4. Mirmiran P, Hosseini-Esfahanil F, Jessri M, Mahan LK, Shiva N, Azizis F. Does dietary intake by Tehranian adults align with the 2005 dietary guidelines for Americans? Observations from the Tehran lipid and glucose study. J Health Popul Nutr. 2011; 29:39–52.
  5. Caspary WF. Physiology and pathophysiology of intestinal absorption. Am J Clin Nutr. 1992; 55:299S–308S.
  6. Mechanick, J. I., Youdim, A., Jones, D. B., Garvey, W. T., Hurley, D. L., McMahon, M. M., Heinberg, L. J., Kushner, R., Adams, T. D., Shikora, S., Dixon, J. B. and Brethauer, S. (2013), Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient—2013 update: Cosponsored by American association of clinical endocrinologists, The obesity society, and American society for metabolic & bariatric surgery*. Obesity, 21: S1–S27. doi:10.1002/oby.20461