BackgroundThe effects of dietary patterns on health outcome of lactating women remain unclear. ObjectivesTo describe the dietary patterns of lactating Japanese women and explore the association between dietary patterns and their general health. MethodsThis study included 1096 lactating women from the Japanese Human Milk Study Cohort. The maternal diet during lactation 1–2 mo postpartum was determined using a FFQ. Dietary patterns were identified using a factor analysis based on the energy-adjusted intake of 42 food items. Trend associations between maternal and infant variables and quartiles of dietary pattern scores were tested, and logistic regression was performed to estimate the OR and 95% CI of maternal self-reporting anemia, constipation, rough skin, sensitivity to cold, and mastitis. ResultsFour dietary patterns were identified in this study. The versatile vegetable diet, characterized by a high intake of vegetables, mushrooms, seaweeds, and tofu, was associated with maternal age, BMI prepregnancy and during the lactation periods, education, household income, and anemia. The plain Japanese diet contained a high intake of typical Japanese foods such as rice and miso soup and a low intake of bread and some confectioneries and was associated with maternal BMI during both periods. The salad vegetable diet, characterized by a high intake of raw vegetables and tomatoes with mayonnaise or dressing, was associated with parity and season in which data collection was conducted. The seafood diet, characterized by a high intake of fish, squid, octopus, shrimp, and shellfish, was associated with days postpartum and sensitivity to cold. ConclusionsFour dietary patterns were identified and were independently associated with socioeconomic factors. The versatile vegetables diet and seafood diet were associated with anemia and sensitivity to cold, respectively, among the participants. This trial was registered at the Japanese Clinical Trials Registry (https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000017649) as UMIN000015494.