Objective  To investigate the association between dietary avoidance of lactating mothers, breast milk composition and physical growth of infants, so as to provide theoretical evidence for promoting healthy development of infants.

Methods Convenient sampling was used to recruit 224 mothers and their babies, who received health check at the outpatient clinic of Xiamen Maternity and Child Health Hospital in Fujian Province from June to December 2022. They were divided into 4 groups: one month, 3 months, 6 months, and 8 moths group. Basic information such as milk and dietary habits were collected, the macronutrient content of breast milk, such as protein, fat, carbohydrate, dry matter, and energy were analyzed, and infant physical growth was measured and evaluated. The association was studied between breastfeeding mother’s diet, milk composition and infants growth.

Results  Avoidance was observed in 19.64% (44/224) of the lactating mothers, and the avoidance rate was 17.01% (33/194) in the exclusively breastfeeding mothers. Among 44 breastfeeding mothers with dietary avoidance, 19 only avoided one kind food, while the other 25 avoided at least two kinds of food. The food that were more avoided were shellfish (15.18%), nuts (7.59%), beans (7.14%), and milk (5.80%). Analysis of the characteristics of breast milk composition was conducted among 194 exclusively breastfeeding mothers. From the 1-month-old group to the 8-month-old group, fat content in breast milk showed an upward trend (F = 2.412, P = 0.068), while the content of total protein and true protein showed a downward trend (F = 2.652, 2.652; all P < 0.001). Compared with none restriction of food, restricted intake of nuts and beans would decrease the content of fat, dry matter and total energy, while restricted intake of fish would decrease the content of total proteins and true proteins in breast milk of lactating mothers (all P < 0.05). From birth to 2 months, the percentage of total protein and true protein over dry mater were positively correlated with the amount of increase of weight for height (WFH) when 120 healthy mothers’(excluding the sample with disease affecting infant physical growth) breast milk composition and infants’ growth index were analyzed (r = 0.33, P = 0.036; r = 0.33, P = 0.037) . On the contrary, fat over dry mater was negatively correlated with the amount of increase of WFH (r = − 0.34, P = 0.029).

Conclusion  The protein content in breast milk gradually decreases with age increases. Dietary avoidance of lactating mothers can affect milk composition, and it is not recommended if not necessarily. Adequate protein intake can promote physical growth and development of infants.