GSTM1 and anemia: The purpose of this study was to assess the effectiveness of intervention with Yingyangbao (YYB) on hemoglobin (Hb) and anemia status among infants and young children (IYC) aged 6–23 months (mo) through a large-scale Nutrition Improvement Program for Children in Poor Areas (NIPCPA) in China from 2015 to 2020.