By Vinod Rane

Over half of patients with symptoms of gastroparesis have low vitamin D levels, which is linked to heightened nausea, vomiting, and gastric neuromuscular dysfunction.

In this observational study, researchers evaluated 513 patients, aged 18 years or older, with symptoms of gastroparesis who are included in the registry of the Gastroparesis Clinical Research Consortium. Patients were enrolled across seven tertiary clinical centers in the United States.

Patients' vitamin D levels were measured at enrollment in the registry. Gastroparesis Cardinal Symptom Index, gastric emptying scintigraphy, and electrogastrography before and after a water load satiety test (WLST) were measured.

Low vitamin D levels were defined as 25-hydroxy vitamin D levels < 30 ng/mL, with 20 to < 30 ng/mL considered insufficient and < 20 ng/mL considered deficient.

The aims of the study were to determine the prevalence of low vitamin D levels in patients with gastroparesis and to examine the relationships among vitamin D levels, symptoms, gastric emptying rate, and gastric myoelectric activity in response to WLST in patients with gastroparesis and those with symptoms but normal gastric emptying.

Of the 513 patients with gastroparesis symptoms, 288 patients (56.1%) had low vitamin D levels, with levels being insufficient in 156 patients and deficient in 132 patients. The prevalence of low vitamin D levels was similar in patients with gastroparesis (54.8%) and with normal gastric emptying (59.9%).

Low vitamin D levels were associated with significantly higher nausea subscores and individual retching scores in patients with gastroparesis and with normal gastric emptying and with higher individual vomiting scores in patients with gastroparesis. It was not associated with increased fullness or bloating in either group.

Patients with gastroparesis and low vitamin D levels showed higher gastric retention of a solid, low-fat meal at 4 hours than those with normal vitamin D levels (36% retention vs 31% retention; P = .05) but not at 1 or 2 hours.

Patients with normal gastric emptying and insufficient and deficient vitamin D levels had increased bradygastria and decreased three-cycles-per-minute gastric myoelectrical activity before ingesting a water load compared with those with normal vitamin D levels (P = .004 for both). After ingesting a water load, they had increased tachygastria (P = .01).

"This study lays the framework for the next level of investigation, replenishment of vitamin D in patients with symptoms of gastroparesis who have low vitamin D levels and see if this improves their gastric neuromuscular dysfunction and symptoms of gastroparesis. Until this study is performed, we advocate assessing vitamin D levels in patients with symptoms of gastroparesis and treatment with exogenous vitamin D if the patient is deficient in vitamin D," the authors wrote.

The study was led by Kenneth L. Koch, MD, from the Section of Gastroenterology, Wake Forest University, Winston-Salem, North Carolina.

The performance of gastric emptying tests and vitamin D level measurements only at registry enrollment could influence the associations observed. Researchers did not compare vitamin D levels with actual dietary intake or explore the correlation between vitamin D levels and symptoms over time. Limitations also included the study's exploratory nature in which multiple comparisons were made.