Herein, we evaluated and compared the dietary and nutrient intakes in LMs from urban and rural areas in China. Quantitative pictures with a visual reference system were used to assist in the dietary survey, which was different from the conventional 24 h dietary recall method. Our findings indicated the need to improve the diet of LMs living in selected 13 provinces and municipalities (urban and rural), although the overall diversity in food consumption was comparable between the two areas.
In our study, we found that although urban women consumed more animal-based foods compared to rural women, the consumption of fish, shrimp, and shellfish did not meet the recommended values in both areas. In the rural areas, consumption of plant-based foods, including vegetables (green leafy and colored), and fruits were low. The consumption of these foods did not meet the Chinese recommended values in both areas. Similarly, both areas showed a low consumption of milk and dairy products, below the Chinese recommended values. Inferentially, LMs, especially in rural areas, should increase the consumption of animal- and plant-based foods to improve the quality of their diet. Limited food varieties and high prices were assumed to be the causes of the insufficient consumption in rural areas. Since Chinese people mainly rely on plant-based foods, especially in rural areas, they do not have the habit of drinking milk. Moreover, in Chinese culture, food taboos restrict the consumption of several foods during lactation, which also contributes to the imbalance in the diets of LMs.
The energy needs of LMs are increased because of breast-milk production [1, 2]; however, we found that of all the LMs from both areas who participated in this study, approximately 83.8% had lower energy intake than the EER value. Lactating mothers, especially in rural areas, should increase dietary intake to meet the lower limit of energy demand. Although the intake of carbohydrates was typically adequate in both urban and rural areas, the energy contribution from carbohydrates failed to meet the requirement, which is consistent with a previous study . In addition, we also found that, the intake of insoluble dietary fiber was not optimistic in both areas due to excessive intake of fine processed food and insufficient intake of vegetables and fruits, which will bring about constipation, hemorrhoids and other health problems to LMs. Compared to non-LMs, LMs require approximately 54% more protein ; they should, therefore, consume more protein foods for optimal production of breast milk to promote infant growth, maintenance, and repair of cells [1, 6]. A study from southeast China found that LMs consumed about 31–53% more protein during the first 3 months of lactation than what was proposed by the Chinese RNI . However, we found that the intake of animal-based food was lower than the recommended amounts. In particular, the consumption of fish, shrimp, shellfish and milk did not meet the recommended values. As a result, protein intake from animal-based foods also failed to reach the recommended value. The possible reason for this difference is that the time of our study is within 24 months after birth. As time goes on, LMs pay less attention to their diet.
A previous study has shown that fat intake in LMs was relatively high in Fujian, southeast China . We found that fat intake, and its contribution to the total energy intake successfully met the required value set by the Chinese DRIs and was within 20–30% of the AMDR. A study on LMs in three cities (Beijing, Guangzhou, and Suzhou) has shown that fat/oil in the women’s diet influenced the fatty acid (FA) composition in breast milk . Although fat plays an important role, whether a link between maternal diet and macronutrients in breast milk exists remains unclear . Three studies from South Korea, Malaysia, and China have found that FAs in breast milk were positively associated with maternal FA intake [25,26,27]. Different types of FAs have different effects on the human body ; high intake of SFAs is a high-risk factor for cardiovascular disease , diabetes, coronary heart disease, stroke, and several types of cancer . However, a high intake of MUFAs can improve serum lipid ratio , and that of PUFAs, including DHA, contributes in improvement in brain function and cognition . Our study found that the intake of SFAs (82.3 and 88.4% in urban and rural areas, respectively) was within the recommended AMDR. Furthermore, the median intake of PUFAs met the required value, but a high percentage of LMs in both groups were below the AMDR. However, the intake of MUFAs was close to the DRI value.
Lactating mothers did not reach the Chinese RNI for all vitamins, except for urban LMs who did so for only VB6. A previous study of LMs in urban areas of China found that they were deficient in VA and VC intake , which were similar to our results. The source of VA is limited, mainly animal liver and dark-green leafy vegetables and fruits. If these kinds of food were not eaten at the time of investigation, the intake level of VA of LMs will be greatly different. The intake of animal liver once or twice a week should be encouraged in the diet of LMs. The intake of fruits and vegetables was lower than the required values, which also explains the lower intake of VC. Meanwhile, the lower intake of cereals, as well as beans and potatoes in the two survey areas, can explain the lower intake of some kinds of VB. Inadequate VB levels can affect the nutrient content of breast milk, thereby leading to growth retardation, anemia, anorexia, and neurological deficits in the infants . The dietary intake of VB is firmly related to the area of residence and socioeconomic status of LMs. Previous studies reported that the intake of VB1, VB2, and VB3 were higher in the urban than in rural areas  and 72% of LMs had lower VB9 intake than the RNI value , which is consistent with our findings. Generally speaking, vegetable oil is the main food in China, and VE is relatively sufficient. In this study, the low level of VE may be related to the difficulty of estimation of dietary oil intake.
In the current study, a notable number of LMs in urban and rural areas failed to meet the EAR for iodine and magnesium and the RNI for iron and zinc. Nevertheless, all of them met the EAR values for phosphorus and copper and the AI for potassium and sodium. In agreement with our study, a previous study from Beijing, Suzhou, and Guangzhou has shown that intake of phosphorus and copper reached the recommended values in all LMs, while more than 50% of them had insufficient intake of iron, zinc, magnesium, and calcium . Since breast milk contains approximately 38% iodine, meeting the iodine requirement during the lactation stage is critical for infants . In view of the findings of our study, it is necessary to ensure that LMs eat seafood once or twice a week and use iodized salt for cooking. Meanwhile, our findings were consistent with those of previous studies reporting low calcium intake due to low consumption of milk during the lactation period [1, 5]. Overall, we found that the intake of key micronutrients essential during lactation, such as iron, calcium, iodine, and zinc was low and did not reach the Chinese recommendation for LMs, indicating the need for additional supplementation to improve the overall nutrient intake. Studies have shown that supplementation of multiple micronutrients improved the nutritional status among LMs [17, 23, 33].
In line with a previous study, our findings also suggested a conflict between the dietary recommendations and traditional practices in the community . In agreement with a previous study , we also argue that single recommendations for a huge country like China are not feasible considering its geographical, cultural, and social-economic diversity. With a population of more than 1.34 billion people, China has 56 different ethnic groups and substantially different dietary patterns [1, 16]. The cultivation of complex food ingredients and eating habits may lead to an imbalance of nutrient intakes under specific conditions . Chinese have a habit of preferring for their own kind of food; such as the northern Chinese prefer to eat more noodles or steam buns and hot spicy food, while the southern Chinese, in general, consume a considerable amount of rice, milk, and cold drinks . It is, therefore, essential that the Balanced Dietary Pagoda and DRIs reflect the regional dietary habits and culture [21, 22]. Based on our findings and that of other studies in China, it would be critical to further track the health and disease risks for LMs and infants who do not receive adequate levels of nutrients. Insufficient nutritional intake directly affects maternal health, by reducing the amount of milk secretion and milk quality, thereby negatively impacting the growth and development of infants [35,36,37]. Accordingly, we recommend that LMs in China should be informed about the need for an appropriate diet to achieve and maintain optimal lactation without depleting mother’s nutrient reserves. Increased intake of fresh vegetables, fruits, fish as well as multivitamins and supplements are recommended for all women, especially for those who do not receive adequate intake of these foods and nutrients. Counseling for nutritional needs is also important for all women (non-LMs and LMs). Overall, a balanced diet is essential for the optimum health of mothers and infants.
However, our study has some limitations. First, we did not record the body weight and height of LMs, socioeconomic status, as well as anthropometrics of the infants as basic information for the study participants. Second, we used quantitative food atlas and a face-to-face dietary survey to help LMs recall the types of food they ate and improve the accuracy of food weight estimation. We also took quality control measures in the process of survey design, implementation, and data collection to minimize any bias. However, the dietary survey itself is very complex, coupled with the special group of LMs, who need postnatal recovery and taking care of infants. These conditions could have caused inevitable bias in data reporting. Third, we used only two-day diet diaries, due to limitation of the interviewers and LMs’ time. The unreasonable diet structures in some LMs might have been due to respondents misunderstanding the questions during the interview, as well as poor education on women’s health and diet. Finally, while we surveyed only healthy LMs, a separate study should focus on the underlying health conditions in those women.