*3.5.2 Calcium*

Calcium absorption occurs mainly in the duodenum and proximal jejunum and is facilitated by vitamin D in an acid environment. Thus, any BS that bypass the first part of the intestine, reduces gastric acid production and lowers vitamin D levels is often associated with reduced calcium absorption [15]. The prevalence of calcium deficiency post LGG and RYGB is 3.9% and 4.3 respectively [37]. Low calcium level may affect bone mineralization, therefore, should be supplemented routinely post BS [8].

## **3.6 Trace elements**

Although most of the literature focuses on calcium and iron, deficiencies of other essential minerals such, zinc, copper, and selenium have been reported in bariatric patients [10]. These essential minerals act as enzymatic cofactors in several biochemical pathways, and therefore, their deficiency could cause variable clinical manifestations that involve neurological, cardiac and gastrointestinal systems. Mineral deficiencies are more common after BPD and RYGB [6].

### *3.6.1 Zinc*

Zinc is absorbed by the small intestine and hence BS such RYGB or BPD/DS which partially exclude nutrient from the small bowel, can cause zinc malabsorption [16]. The prevalence of zinc deficiency is 23.9% after LSG [38]. Moderate zinc deficiency presents with hypogeusia, hyposmia, anorexia, eczema, somnolence, and reduced dark adaptation, whereas severe forms are associated with acrodermatitis enteropathica, bullous or pustular dermatitis, diarrhea, balding, mental abnormalities including depression, and recurrent infections due to impaired immune function [16].

#### *3.6.2 Copper*

Copper functions as a cofactor in many enzymatic reactions that are vital for the hematologic, vascular, skeletal, antioxidant, and neurologic systems [39]. It is absorbed mainly in the stomach and proximal duodenum. Copper deficiency is rare and underrecognized. More recently, it has been reported after malabsorptive procedures [39]. Symptoms of copper deficiency are often similar to symptoms of vitamin B12 deficiency (hematological and neurological problems). Peripheral neuropathy, myeloneuropathy with spastic ataxic gait have been reported after BS [40]. Recently, a case of severe pancytopenia with refractory anemia secondary to

copper deficiency has been observed after BS [39]. In this case, administration of intravenous copper resulted in dramatic clinical improvement [39].
