The purpose of this study was to elucidate the dietary factors that influenced serum folate. Data were obtained from 33 vegetarians and 63 omnivorous middle-aged voluntary women. The vegetarian diet consisted mainly of unpolished rice, green vegetables, and tofu (bean curd), under a physician’s guidance, and there were individual variations. Serum folate concentrations were measured by chemiluminescent immunoassay. The BMI, % body fat, waist circumference, and diastolic pressure in the vegetarian group were significantly lower than those in the non vegetarian group. The intakes of Ca, Mg, Fe, Mn, retinol activity equivalents, vitamin K and vitamin B1 in the vegetarian group were significantly more than those in the non vegetarian group. The serum folate and the blood rheology in the vegetarian group were significantly higher than in the non vegetarian group. A factor analysis using prin- cipal components extraction with promax rotation was performed on the variables of physique, body composition, hematological parameters, nutrient intake, and food intake. Ten components were extracted and subjected to path analysis. The hypothesized model fitted well (GFI, AGFI, RMR, RMSEA, and AIC). The results showed that “vitamins, minerals” and “serum proteins” directly increased, and “energy source” directly decreased the serum folate. Indirectly “pulses and green vegetables” increased, and “animal foods” decreased the serum folate. These findings are consistent with the hypothesis that the vegetarian diet directly and indirectly increases the serum folate and subsequently reduces plasma homocysteine and might to attributable to cardiovascular disease and Alzheimer disease.