Children who have lowered levels of zinc have a greater number of instances of diarrhea, severe diarrhea, and diarrhea associated with fever. Similarly, vitamin A deficiency can cause an increase in the severity of diarrheal episodes. However, there is some discrepancy when it comes to the impact of vitamin A deficiency on the rate of disease. While some argue that a relationship does not exist between the rate of disease and vitamin A status, Others suggest an increase in the rate associated with deficiency. Given that estimates suggest 127 million preschool children worldwide are vitamin A deficient, this population has the potential for increased risk of disease contraction. Malabsorption
Malabsorption is the inability to absorb food fully, mostly from disorders in the small bowel, but also due to maldigestion from diseases of the pancreas. Causes include:
enzyme deficiencies or mucosal abnormality, as in food allergy and food intolerance, e.g. celiac disease (gluten intolerance), lactose intolerance (intolerance to milk sugar, common in non-Europeans), and fructose malabsorption. pernicious anemia, or impaired bowel function due to the inability to absorb vitamin B12,
loss of pancreatic secretions, which may be due to cystic fibrosis or pancreatitis,
structural defects, like short bowel syndrome (surgically removed bowel) and radiation fibrosis, such as usually follows cancer treatment and other drugs, including agents used in chemotherapy; and
certain drugs, like orlistat, which inhibits the absorption of fat. Inflammatory bowel disease
The two overlapping types here are of unknown origin:

Ulcerative colitis is marked by chronic bloody diarrhea and inflammation mostly affects the distal colon near the rectum.
High resolution esophageal manometry will show elevated pressure at the LES with normal peristalsis. The LES pressure is evaluated immediately following a swallow, when the sphincter should relax. The overall LES pressure after a swallow is represented by the integrated relaxation pressure (IRP). If the IRP is abnormally elevated (>15 mmHg), this indicates an obstruction is present. Normal peristalsis with an obstruction at the esophagogastric junction (elevated IRP) is consistent with EGJOO.Upper endoscopy is used to evaluate for mechanical causes of obstruction. Endoscopic findings may include a hiatal hernia, esophagitis,  strictures, tumors, or masses. Increased pressure at the LES over time may result in an epiphrenic diverticulum. Further evaluation for mechanical causes of obstruction may include CT scans, MRI, or endoscopic ultrasound.Several additional tests may be used to further evaluate EGJOO. Further evaluation of esophageal motor function may be accomplished with functional lumen imaging probe (FLIP). Although not widely available, FLIP may help assess esophageal wall stiffness and compliance. FLIP may help identify individuals with EGJOO who are likely to benefit from therapeutic procedures.Timed barium esophagram can help distinguish EGJOO from untreated achalasia. Treatment
Treatment primarily consists of addressing the underlying cause of EGJOO. For example, gastroesophageal reflux disease (GERD) with reflux esophagitis is treated with proton pump inhibitors. Esophageal rings or strictures may be treated with esophageal dilation. Simple observation may be considered, especially if symptoms are minimal or absent.