Iron

Iron deficiency is very common after gastric bypass, occurring in 33
to 50 percent of patients. Serum ferritin is the most sensitive marker for
storage iron, and thus can be used by the provider as an early indicator of
iron deficiency. Heme iron is the form found in animal protein and is the
most effectively absorbed. However, intolerance of red meats (good heme iron
sources) and other meats can be a problem in many patients. The duodenum and
proximal jejunum are the primary sites of iron absorption, and in gastric
bypass, the duodenum is bypassed.

Nonheme (plant) or inorganic forms of iron are relatively inexpensive and
readily available over the counter. Supplementation with ferrous forms of
iron is common practice in post-weight loss surgery patients. Inorganic
forms of iron can cause gastrointestinal disturbances, such as constipation
and its associated discomfort. Adequate stomach acid is needed for
absorption of nonheme iron and there is decreased hydrochloric acid
production with all of the types of bariatric surgery. Proton pump
inhibitors (PPIs) are commonly used in weight loss surgery patients, thus
decreasing stomach acid production.

It is common practice to recommend separating iron supplements from calcium
supplements by 1 to 2 hours due to competition for absorption in the
gastrointestinal tract. However, in a study examining the effect of adding a
calcium-rich food to a meal containing both heme and nonheme forms of iron,
there were several useful observations. The addition of a calcium-rich food
did not impair absorption of either heme or nonheme iron. Heme iron
absorption may take longer and continue further down the intestine than
nonheme iron. Provision of a nonheme iron supplement appears to be
effectively absorbed if given with a heme form of iron (generally a meal
consisting of meat).[40] Consumption of vitamin C (ascorbic acid) or a
source of food high in vitamin C is frequently recommended to provide an
acidic environment to improve nonheme supplement forms of iron.

In renal bariatric patients, anemia management could be an even bigger
challenge. In patients with CDK, iron deficiency is common and anemia
management is complex. In patients with CKD who are not on dialysis,
provision of either oral iron or intravenous (IV) iron may delay the need
for erythropoiesis-stimulating medications. Patients on hemodialysis are
less able to absorb oral iron due to elevated serum levels of hepcidin,
which also impairs ability to recycle iron in the normal reticuloendothelial
system. IV iron is more effective in hemodialysis patients to increase
ferritin and decrease the need for erythropoetic-stimulants.