Table 2. Studies on vitamin D intake and serum vitamin D status in the patients with gastric cancer.

Study design	Participants	Exposure to	Methods of measurement	Outcome	Summary of findings	References (year, country)
Case–control (7y)	723 cases 2,024 controls	Vitamin D intake	Diet history	Risk of gastric cancer	Positive correlation OR:1.35 95%CI:1.00-1.83	Vecchia et al. (1994, Italy)
Case-control (10y)	230 cases 547 controls	Vitamin D intake	Food frequency questionnaire	Risk of gastric cancer	No significant correlation OR:1.33 95%CI:0.80-2.21	Pelucchi et al. (2009, Italy)
Prospective cohort(24y)	1,105 people	Serum 25(OH)D	ELISA	Mortality of upper gastrointestinal cancers	No correlation HR:0.97 95%CI:0.88-1.06	Lin et al. (2012, China)
Prospective cohort( 5.25y)	2084 people	Serum 25(OH)D	ELISA	Risk of gastric cancer	No significant correlation HR:1.77 95%CI:1.16– 2.70	Chen et al. (2007, China)
Pooling project	1,065cases 1,066 controls	Serum 25(OH)D	ELISA	Risk of gastric cancer	Inverse correlation OR=0.65（＞100nmol/L） 95%CI:0.26-1.62	Abnet et al. (2010, US, Finland and China)
Prospective cohort(14y)	51,529 men	Predicted 25(OH)D	Model predicting 25(OH)D	Risk of gastric cancer	Inverse correlation RR = 0.58 95%CI=0.26-1.33	Giovannucci et al. ( 2006, US)
Retrospective case-control	49cases 49controls	Serum 25(OH)D	ELISA	Risk of gastric adenocarcinoma with VD deficiency	Positive correlation OR=3.8 95%CI:1.42-10.18	Vyas et al. (2016, US)
Case-control	68 cases 20 controls	Serum 25(OH)D	ELISA	Level in gastric cancer	Increased in gastric cancer P=0.036	Fidan et al. (2010, Turkey)
Observational study	197cases	Serum 25(OH)D	ELISA	An independent prognostic factor of gastric cancer	Inverse correlation P=0.019	Ren et al. (2012, china)
Prospective cohort	43,468White men 481 Black men	Vitamin D Intake	Dietary questionnaire	Gastric cancer mortality and incidence with hypovitaminosis D	Increased incidence RR=1.57 95% CI=1.16-2.11 Increased mortality RR=2.27 95%CI=1.57-3.28	Giovannucci et al. (2006, US)