When it comes to metabolic and bariatric surgery (MBS), many of us are well aware of a procedure’s long-term benefits beyond the obvious: improved psychological health and self-esteem and improved overall well-being. While each of these can undoubtedly improve one’s quality of life, the reality is that optimal health depends on consistent daily habits, whether one has undergone surgery or not. In the case of MBS patients, special care must be taken to ensure that the diet provides adequate nutrition, since many bariatric procedures involve changes to the anatomy that affect the absorption of macro- and micronutrients (vitamins and minerals). Failure to maintain adequate micronutrient status puts one at risk for compromised health in the form of various conditions caused by nutrient deficiencies (bone loss, anemias, neurological disease, and muscle wasting, among others) regardless of surgery status. This blog focuses on blood health and nutritional status.

Anemia is a condition characterized by red blood cell or hemoglobin deficiency in blood. Although its causes can be diverse, for MBS patients this condition is usually induced by a micronutrient deficiency. Contrary to popular opinion, anemias are not limited to deficiency in iron; they may be induced by other nutrient inadequacies and are considered the “most common nutritional deficiency” following a bariatric procedure.1 Iron, folate, and B12 are critical for red blood production, but research has also established that copper and zinc levels both impact iron absorption and utilization.2 Other deficiencies cited as potential contributors to anemia include vitamins A and E.3 It is easy to understand how anemia can be driven by deficiencies of a handful of vitamins and minerals!

Reduced intake due to intolerance/aversion and the ability to eat only limited quantities of food after MBS can ultimately affect vitamin and mineral status. Although it is often believed that gastric bypass patients are at higher risk for developing a nutritional anemia compared to sleeve gastrectomy patients, a recent study comparing rates of anemia and deficiency among patients who had either one of these procedures found a similar risk for postoperative anemia and iron deficiency between the two, although the incidence of risk for B12 deficiency appeared to be higher among the gastric bypass population.4

It is sometimes easy to mistake anemia for other conditions. Some common symptoms that occur with anemias include dizziness, fatigue, headache, lightheadedness, rapid heart rate, shortness of breath, and weakness. Brittle nails can be a physical manifestation of anemia. None of these symptoms are unique to anemia, often a reason why this condition goes undiagnosed. It is important to be mindful of any changes in the way patients feel, especially if they experience one or more of these.

The role of micronutrients in general health after MBS

Taking care to eat a varied diet that includes sources of iron, folate, and B12 (as well as taking vitamin and mineral supplements as recommended by your health care provider) is essential to prevent anemia. Iron and folate can be found in plant foods, but B12 can only be obtained in the diet through poultry, meat, fish, and egg consumption. Sources of iron include beans, nuts/seeds, dried fruit, liver, meat, eggs, and fish. ABCDs (asparagus, avocado, beans, broccoli, Brussels sprouts, citrus, and dark leafy greens) contain folate.

Because metabolic and bariatric procedures can affect tolerance and intake, it is recommended that patients follow a regimen including these nutrients to keep anemia at bay. Guidelines for these nutrients, established by the American Society for Metabolic and Bariatric Society, follow:


18 mg/d
45-60 mg/d menstruating females and/or SG, RYGB, or BPD/DS

Vitamin B12

350–500 mcg/d

Vitamin A

5,000 IU LAGB
5,000-10,000 IU RYGB and SG
10,000 IU DS


400–800 mcg/d
800–1,000 mcg/d (women of childbearing age only)


200% of the RDA for copper (2 mg/d) BPD/DS or RYGB
100% of the RDA for copper (1 mg/d) SG or LAGB


Multivitamin with minerals containing 200% of RDA (16–22 mg/d) BPD/DS
Multivitamin with minerals containing 100–200% of RDA (8–22 mg/d) RYGB
Multivitamin with minerals containing 100% of RDA (8–11 mg/d) SG/LAGB

*In the post-MBS patient, supplementation with 1 mg copper is recommended for every 8-15 mg of elemental zinc to prevent copper deficiency.



  1. Lee YC et al. Predictors of anemia after bariatric surgery using multivariate adaptive regression splines. Hepatogastroenterology. 2012 Jul-Aug;59(117):1378-1380.
  2. Chan LN et al. The science and practice of micronutrient supplementations in nutritional anemia: an evidence-based review. JPEN J Parenter Enteral Nutr. 2014 Aug;38(6):656-672.
  3. von Drygalski A et al. Anemia after bariatric surgery: more than just iron deficiency. Nutr Clin Pract. 2009 Apr-May;24(2):217-226.
  4. Kwon Y et al. Anemia, iron and vitamin B12 deficiencies after sleeve gastrectomy compared to Roux-en-Y gastric bypass: a meta-analysis. Surg Obes Relat Dis. 2014 Jul-Aug;10(4):589-97.