Differences in Complementary Feeding of 6 to 23 Month Olds in China, US and Mexico

sufficient to meet the nutritional needs of the infant [1]. The transition from exclusive breastfeeding to family foods, referred to as complementary feeding, typically covers the period from 6 to 18-24 months of age [1]. Since children under two years of age have high nutrient needs to support their rapid growth and development but consume relatively small amounts of food at a time, complementary foods need to be far more nutrient-dense than foods consumed by adults [2].


Introduction
The introduction of suitable complementary foods at the appropriate time is essential for the optimal growth and development of infants and young children.Complementary foods should be added to the diet when breast milk is no longer The MING study was a cross-sectional study to investigate the dietary and nutritional status of pregnant women, lactating mothers, and infants and young children conducted in 2011 and 2012 [6,13].Infants and young children aged from birth to 35 months were recruited from maternal and child care centers (MCCC) in eight cities in China.In each city, two MCCC were selected and subjects were recruited randomly based on the child registration list in each of the MCCC until the target number was reached.The study was conducted according to the guidelines in the Declaration of Helsinki.All of the procedures involving human subjects were approved by the Medical Ethics Research Board of Peking University.Written informed consent was obtained from the primary caregiver of each child participating in the study.A total of 906 of infants and toddlers aged 6-23 months were included in the current analysis.
The FITS 2008 was a national sample of US children aged from birth through age 47 months [11].Subjects were recruited and interviews were conducted by telephone.All instruments and procedures were reviewed and approved by Mathematica Policy Research's independent institutional review board (Public/ Private Ventures, Philadelphia, PA).A total of 1430 of infants and toddlers aged 6-23 months were included in the current analysis.
The Mexican NHNS 2012 was a cross-sectional population based survey to characterize the health and nutritional status of the Mexican population.The survey used a multi-stage, stratified and clustered sampling system drawn to be representative of all states and four geographic regions in Mexico [12].The survey protocol and data collection instruments were approved by the Ethics Committee of the Mexican National Institute of Public Health.A total of 767 of infants and toddlers aged 6-23 months from the NHNS were included in the current analysis.

Dietary data collection
In the MING study in China and NHNS in Mexico, one 24-hour dietary recall was collected for each child through a face-to-face interview by trained interviewers with the parent or caregiver.
The interviewers asked about all foods and beverages and the amount consumed of each food item for the previous 24-hour period.Portions were estimated using common household measurement aids (including spoons, cups and bowls) and the information was then converted to grams.A picture booklet of common foods consumed was also used to estimate the amount of foods and beverages in the MING study.
In FITS, two 24-hour dietary recalls were collected via telephone interview conducted by certified dietary interviewers at the University of Minnesota's Nutrition Coordinating Center using the Nutrition Data System for Research (version 2008, University of Minnesota Nutrition Data System for Research, Minneapolis).Before the dietary interview, the main caregiver of the selected child was mailed a packet of materials, including food model booklet, ruler, and liquid measuring cup with instructions for estimating amounts of foods and beverages consumed.Food intake data collected on first day of the two 24 hour recalls was used in the present analysis.
All foods and beverages reported were assigned to food groups adapted from FITS [14].Food groups were adjusted for China and Mexico to incorporate local foods and reflect the relative role of specific types of foods in the diets of infants and toddlers living in those countries.In China, fortified milk power produced specifically for young children aged 1-3 years, called growing-up milk, is commonly consumed by young children from 12 months onwards.In this study, infant formula and growingup milk were grouped into one category called infant formula/ growing-up milk.
Breast milk consumption was estimated based on the child's age in months and the total amount of other milks (infant formula and cow's milk) reported over the course of the recall day [7,15].The same estimates were used for children in all three countries.For infants aged 6 to 11 months fed human milk as the sole milk source, the amount of human milk was assumed to be 600mL/ day.For partially breastfed infants, the amount of human milk was computed as 600mL/day minus the amount of formula/ other milks consumed.For breastfed young children aged 12 to 17 months, the amount of human milk was computed as 89 mL per feeding occasion.For breastfed young children aged 18 to 23 months, the amount of human milk was computed as 59 mL per feeding occasion [7,15].

Analytic methods
Average amount of foods and beverages consumed in grams per capita and Standard Errors (SE) were calculated using the Statistical Analysis System (version 9.1.3,2004, SAS Institutes, Cary, NC).In FITS and NHNS, all estimates incorporated appropriate sample weights to reflect nationally representative results and to account for survey design.In the MING study, sample weighting was not carried out as the study was not designed to collect a nationally representative sample [6].To understand complementary food consumption in detail and changes with age, average amounts of complementary foods consumed were presented for three age groups: 6-8 months, 9-11 months and 12-23 months for each country.Differences in mean intake between age groups in each country and differences in mean intake between countries for the same age group were tested by using Student's t tests.A null hypothesis was rejected at an α level that controls the overall type I error rate at 5% by using Bonferroni correction for multiple comparisons [16].

Milk
Breast milk constituted about half of the milk intake and formula the other half among 6-8 month olds in both China and Mexico (Table 1).In the US, breast milk was consumed at a lower level and the level remained unchanged among 9-11 month olds.In China, breast milk consumption decreased significantly by 9-11 month (p<0.01).By 12-23 months, breast milk consumption decreased sharply in all counties (p<0.01)(Table 1).
Large differences were seen in formula/growing-up milk and cow's milk consumption across countries.In China, infant formula/growing-up milk was the major source of milk consumed across all age groups and its consumption was still high at 12-23 months, with an average amount of 317 g/d (equal to approximately 1.25 cups per day) (Table 1).On the other hand, cow's milk consumption was very low across all age groups.In the US, at 6-8 months and 9-11 months, infant formula was consumed at a higher amount (526 g/d and 484 g/d, respectively), nearly twice as much as what was consumed among Chinese infants (p<0.01).By 12-23 months, cow's milk became the major source of milk with children consuming on average 408 g/d (equivalent to 1.7 cups per day).In Mexico, infant formula was consumed both before and after 12 months but the amount was lower after 12 months (p<0.05).It was also observed that in the Mexican population cow's milk was already consumed at a significant amount (210 g/d) by 9-11 months compared with other two countries (p<0.01) and it remained to be the main source of milk at 12-23 months (Table 1).

Grains
In China, infant cereal was one of the main grain sources at both 6-8 months and 9-11 months (Table 1).Rice was another main grain source at 6-8 months and its consumption increased steadily and sharply with age (p<0.01).By 12-23 months the average amount of rice consumed was 96 g/d.In the US, infant cereal was the major grain source at 6-8 months and family cereals became another major grain source from 9-11 months onwards.Rice and pancakes/tortilla were consumed at a lower amount (Table 1).Among Mexico children, pancakes/tortilla was the major grain source by 12-23 months (29 g/d).Other grains including infant cereal, family cereals and rice were also consumed (Table 1).

Desserts/sweets/sugar-sweetened beverages and fruit juice
For desserts/sweets/sugar-sweetened beverages (SSB) and fruit juice, distinct consumption patterns were observed.In China, desserts/sweets/SSB or fruit juice were rarely consumed (Table 2 and Fig. 1), whereas in the US, sweet food and beverage consumption increased steadily with age (p<0.05), with SSB the largest contributor at 12-23 months.In Mexico, similar patterns to the US, but on a very different scale, were observed.SSB consumption was 2 fold higher at 9-11 months and more than 3 fold higher at 12-23 months than in the US.The average amount of SSB was 219 g/d at 12-23 months (Table 2 and Fig  1).Although the consumption of SSB in the US was not as high as that in Mexico, 100% fruit juice however was highly consumed (p<0.01).The average amount was 139 g/d at 12 to 23 months (approximately 1/2 cup).

Fruit and Vegetables
Generally, before 12 months of age consumption of vegetables, especially different types of colored vegetables, was low in Mexico and China, compared to the US (p<0.05)(Table 3).In China, any vegetable consumption increased at 12-23 months (p<0.05),whereas in the US any vegetable consumption peaked between 9-11 months, then decreased at 12-23 months (p<0.05)(Table 3).The higher vegetable consumption in the US can be attributed to the consumption of vegetable baby food (61 g/d at 6-8 months and 42 g/d at 9-11 months) (Table 3).In Mexico, any vegetable consumption fluctuated at a lower level compared with other two populations and no age related change was observed.However, the amount of vegetables consumed was likely underestimated as it was not possible to disaggregate vegetables from mixed dishes in the Mexico survey.
Any fruit consumption was higher in the US than in China at 6-8 months and at 9-11 months (p<0.05)(Table 2).Again, fruit baby foods were a major contributor to overall fruit consumption in the US, but rarely or little consumed in China and Mexico (p<0.01).Any fruit consumption at 9-11 months increased significantly from 6-8 months in the US (p<0.01) but this was not observed in China and Mexico.

Differences in Complementary Feeding of 6 to 23 Month Olds in China, US and Mexico
Copyright: © 2016 Denney, et al.

Meats and protein foods
Eggs were the dominant protein source in China across all age groups (Table 3).The amount consumed ranged from 24 g/d at 6-8 months (about 1 egg every other day) to 39 g/d at 21-23 months (equal to more than three quarters of one egg per day).Pork/ham was the second most consumed protein food among the Chinese children but was rarely consumed in the US or Mexico.Eggs were also a major protein source among Mexican infants and toddlers together with other protein sources including yogurt and dried beans/peas, whereas a variety of protein sources were consumed in the US with yogurt and chicken/turkey being top sources (Table 3).

Discussion
We have previously reported the percentage of children consuming foods from specific food groups in the three populations [8][9][10].The present study provides further insights by reporting quantities of the foods consumed and comparing the data across the three culturally diverse populations.
Cow's milk consumption was low in infants and toddlers in China.This is largely because milk or dairy products are not habitually consumed in the Chinese population.Over the past few decades, some increase in milk and dairy consumption has been reported in China, but dairy consumption is still low [17].On the other hand, infant formula and fortified milk powder is widely used [18,19].We reported previously that 59% infants consumed infant formula and 53-75% of young children consumed growing-up milk in the MING study [10].As a result, infant formula/growing up milk became top food sources of energy and many key nutrients in this population [13].The high amount of infant formula/growing-up milk consumed found in the current analysis indeed confirmed our previous findings.
A significant amount of cow's milk was consumed by the Mexican infants aged 9-11 months.Cow's milk is considered an inappropriate milk for children under the age of 1 year [20] as early feeding of cow's milk is associated with an increased risk of developing iron-deficiency anemia [21].This is a key concern because iron-deficiency anemia is already prevalent (23%) among young children in Mexico [22].
To prevent iron-deficiency anemia in infancy, consumption of iron-fortified infant cereal in the second half of infancy is recommended by infant feeding guidelines in all three countries [23][24][25].However, the amount of infant cereal was found to be lower among 9 to 11 month olds compared to amounts consumed at 6 -8 months in China and infant cereal consumption was low overall in Mexico, compared with other two countries (p<0.01)(Table1).In the case of China, we reported previously that a high proportion of infants consumed rice and rice was the number two source of energy by 12-23 months [10,13].The high rice consumption is in line with a recent review on introducing solid foods to infants in the Asia Pacific Region [3].The authors reported that rice porridge or rice paste was the first and most popular food introduced to infants in China, Viet Nam and Japan.This is because rice is a local staple food and also culturally believed to help with digestion.However, refined rice or rice products are of low energy and micronutrient density.Without fortification refined rice products provide insufficient quantities of iron, zinc and calcium.When such foods that are poor sources of nutrients become major sources in the diet, the risk of nutrient shortfall could exist [6].
In the US, family cereals were a major grain source from the age of 9-11 months while infant cereal consumption was diminishing.Ready-to-eat cereals are often fortified with micronutrients, though generally at a lower level than fortified infant cereal.Indeed, family cereals were reported to be top sources of iron and zinc among infants and young children from FITS previously [14].To a lesser extent, family cereals were also consumed among the Mexican children and a variety of other grains were consumed by Mexican children including pancakes/ tortilla, pasta, noodles and rice.Large differences were found in SSB and fruit juice consumption.SSBs were rarely consumed among the Chinese children but were heavily consumed among the Mexican children with the average amount alarmingly high.The high amount of SSB consumption adds further insight to our previous report that 63-78% of the Mexican children consumed SSB on the day of dietary recall [8].SSBs such as water-and milk-based atoles, Aguas Frescas, fruit flavored drinks, sweetened tea and carbonated soft-drinks were the primary sources of added sugar in the diet of children.Consumption of SSBs has been positively associated with overweight and obesity in infants and children in Mexico, US and UK [26,27].Obesity during childhood and adolescence is of major concern given that obese children and adolescents are at higher risk of being obese adults and developing comorbidities, such as diabetes and cardiovascular diseases [28][29][30].
Although fruit juice is a major source of vitamin C and potassium, 100% fruit juice consumption has been questioned as another high-calorie, high sugar food increasing likelihood of obesity in preschoolers [31][32][33].The American Academy of Pediatrics recommends limiting juice to 4-6 ounces per day for children ages 1-6 years [34].The average amount of fruit juice consumed by toddlers 12-23 months in FITS was about 5 ounces per day.Considering these children's young age, the consumption of fruit juice should be closely monitored and perhaps reduced among high consumers.
We acknowledge that our study has limitations.First, all children in the MING study were recruited from the MCCC in selected cities in China, Therefore, it was an urban rather than a nationally representative sample.Indeed, it has been reported that the proportion of young children consuming meat or milk is higher in urban than in rural areas in China [35].Therefore, the MING data reported in this study reflects mainly complementary feeding practices in urban areas of China.Second, the information on food consumption in China and Mexico was based on one 24-h dietary recall.It is possible that for some children the recall day was not typical of their usual dietary pattern.However, validated methods for collection by trained interviewers and the large sample sizes may help to minimize these issues [36].Nevertheless, a major strength of our study is the use of same age categories and food groups to describe the complementary food intake and transitions across the ages of 6 to 23 months in three countries representing different parts of the world.

Conclusions
This study described the infant feeding transitions across the ages of 6 to 23 months in three culturally diverse populations.Complementary food consumption varied considerably across the three countries.This study confirmed and provided additional detail about some problematic feeding patterns identified earlier across the three countries, including early introduction of relatively high amounts of empty calorie foods, such as SSB and sweets in Mexico and US, and high consumption of low-nutrient dense foods such as refined rice in China.We also observed an early introduction of cow's milk in Mexico along with low intake of iron-rich foods like iron-fortified infant cereal.Infant feeding guidelines should be culture-specific and food-based.The findings from the study will help healthcare professionals to target advice to parents on improving complementary feeding practices in these countries.

Figure 1 :
Figure 1: Sugar sweetened beverage (SSB) and 100% fruit juice consumption of infants and toddlers from China, US and Mexico.

Table 1 :Food
Daily consumption per capita of milk and grain food of infants and young children from China, the US and Mexico error) g/d Citation: Denney L, Reidy KC, Eldridge AL (2016) Differences in Complementary Feeding of 6 to 23 Month Olds in China, US and Mexico.J Nutrition Health Food Sci 4(6): 1-8.DOI: http://dx.doi.org/10.15226/jnhfs.2016.00181Differences in Complementary Feeding of 6 to 23 Month Olds in China, US and Mexico Copyright: © 2016 Denney, et al.

Table 2 :
Daily consumption per capita of fruits and desserts, sweets and sugar-sweetened beverages of infants and young children from China, the US and Mexico Denney L, Reidy KC, Eldridge AL (2016) Differences in Complementary Feeding of 6 to 23 Month Olds in China, US and Mexico.J Nutrition Health Food Sci 4(6): 1-8.DOI: http://dx.doi.org/10.15226/jnhfs.2016.00181