Dietary supplements enriched with vitamins, minerals, and other substances have received considerable attention worldwide. North America and the Asia Pacific region are the dominant markets for vitamins and dietary supplements (1). In 2002, expenditures on dietary supplements in the United States was approximately US$18.7 billion (2), and in the Taiwan marketapproximately NT$23 billion (US$718 million) (3). Most surveys have focused on the use of supplements in adults, but little is known regarding the intake of supplements by infants. In addition, little is known regarding the type of dietary supplements that parents provide for infants, and which types of parents are more likely to do so. In the United States, approximately 10% to 20% of young children consume supplements (4,5). Dietary supplements are designed to enhance health and wellness (6), and taking dietary supplements can be beneficial when dietary intake is inadequate. However, adverse effects may be induced by inappropriate use (7,8), and some supplements are supported by little scientific evidence regarding safety or efficacy.
Nutritionally, infancy is a critical period in which children are particularly vulnerable. At no other stage of life is consuming a single food adequate as the sole source of nutrition (9). To promote the health of infants and children, the World Health Organization (WHO) recommends that infants be exclusively breast-fed for the first 6 months of life and that they should continue to receive human milk for the remainder of their first and second years (10). Deficiencies in fat-soluble vitamins D and K among breast-fed infants have been well documented, and supplementation of these 2 vitamins is recommended by the American Academy of Pediatrics for breast-fed infants ages younger than 6 months (11). In Taiwan, infant feeding policies follow WHO recommendations concerning breast-feeding (12), and no advice regarding the use of infant supplements is presently available.
Because young children, particularly infants, are more vulnerable to the adverse effects of dietary supplements, the present study was performed to investigate the types of dietary supplements used for healthy 6-month-old infants and to identify the factors influencing such use.
SUBJECTS AND METHODS
The Taiwan Birth Cohort Study is a prospective longitudinal cohort study using a stratified multistage systematic sampling design to obtain representative samples from the 2005 Taiwan National Birth Registration Data. A total of 369 towns were sorted into 12 strata based on administrative divisions (4 strata) and fertility rates (3 strata). Using the principle of probability proportionate to size, we randomly selected 85 primary sampling units (from 90 of 369 towns) from the 12 strata. A total of 24,200 pairs of parents and newborns were recruited to participate in the study. All of the participants provided informed consent, as approved by the ethics review board of the College of Public Health, National Taiwan University. The present study was conducted according to the guidelines outlined in the Declaration of Helsinki.
Basic demographic information for the parents and infants was obtained from the Taiwan National Birth Registry. Between June 1, 2005 and July 31, 2006, we interviewed 24,000 women in their homes 6 months after childbirth using a structured questionnaire. Interviews were completed by 21,248 couples for a completion rate of 87.8%. After excluding low-birth-weight infants (those <2500 g), preterm babies (<37 gestational weeks at birth), and incomplete questionnaires, 18,658 cases constituted the final valid sample of the present study.
The present study used the following outcome measures: whether the infant was given any dietary supplement in the first 6 months after birth; and the type of supplement received.
Infant Feeding Practices and Potential Confounding Variables
We obtained data related to infant feeding methods and other sociodemographic variables from the Taiwanese national birth registry and interview questionnaires. Infant feeding types were stratified into 3 groups: formula-fed, ever breast-fed from birth (ever breast-fed), and still breast-fed at 6 months. The time at which complementary feeding began was stratified into 3 groups: before the fourth month, between the fourth and sixth months, and after the sixth month. The age levels of mothers were grouped into 2 categories: younger than 30 years; and 30 years old or above. We stratified the educational level of mothers into 2 groups: university/college or above; and high school or below. The nationality of mothers was classified as Taiwanese or foreign-born. The use of supplements during pregnancy was classified as “yes” or “no.” Family monthly income was stratified into 3 groups defined as total family income per month in New Taiwan dollars (NT$): <NT$50,000; NT$50,000–NT$99,000; and NT$100,000 or above (US$1 = approximately NT$32 in 2005). Household urbanicity was divided into 3 groups: urban; main street in rural area; and rural. Infant-related variables included sex, birth order, allergic status (defined as the infant having either atopic dermatitis or seborrhea dermatitis), and the family history of allergies (defined as the parents having either asthma, atopic dermatitis, or allergic rhinitis).
A χ2 test was performed to assess the differences in basic characteristics and factors potentially related to the use of supplements among infants of various groups. Multiple logistic regression was performed to estimate odds ratios (ORs) with 95% confidence intervals for supplement use following adjustment for the potential confounding effects of the age, educational level, or nationality of the mother, as well as the use of supplements during pregnancy, household income, sex of the infant, and birth order. The statistical threshold for significance was set at P = 0.05. Statistical analysis was conducted using the SPSS version 12.0 (SPSS Inc, Chicago, IL).
Types of Supplements Used by Infants
Table 1 lists the types of supplements used. Approximately one-third of the infants (34.9%) had been fed a dietary supplement between birth and 6 months of age. The majority of supplement users (64.9%) received only 1 type of supplement in the first 6 months of life, whereas 24.8% received 2 types of supplements, and 10.3% received 3 or more types of supplements. The most common types of infant supplements were probiotics, calcium, and multivitamin/mineral supplements. Among supplement users, 44.9% of infants received probiotics, 44.4% received calcium, and 37.0% received multivitamin/mineral supplements.
Prevalence of Supplement Use
Several maternal characteristics were associated with the use of infant supplements (Table 2). Maternal nationality, the use of supplements during pregnancy, and household income were significantly related to the use of all types of infant supplements. The age of the mother was only significantly related to the use of infant calcium supplements, whereas educational level was significantly related to the use of infant probiotics, calcium, and multivitamin/mineral supplements. Infants of mothers with higher educational levels were more likely to receive probiotics and multivitamin/mineral supplements. Infants of mothers with less education were more likely to receive calcium supplements.
Table 3 shows several characteristics of infants associated with the use of supplements. Infants who were male, first-born, ever breast-fed, or had received complementary feeding during their first 4 months of life were more likely to receive dietary supplements than other infants. The prevalence of the use of probiotics, calcium, and multivitamin/mineral supplements was lowest in the group still breast-fed at 6 months, and highest in the ever breast-fed group. The prevalence in the use of probiotic, calcium, and multivitamin/mineral supplements was lowest among infants whose complementary feeding began after 6 months and highest among infants whose complementary feeding began before the fourth month. The prevalence in the use of probiotic supplements was significantly higher among infants with allergies. Infants with a family history of allergies were also significantly more likely to receive probiotics and multivitamin/mineral supplements.
Predictors of Infant Dietary Supplement Used
Table 4 presents multivariate model analysis of the adjusted ORs with 95% confidence intervals for the use of supplements during pregnancy, infant feeding practices, and variables related to allergies. After adjustment for other confounding variables, earlier habits of mothers regarding the use of supplements and infant feeding practices were found to be significantly associated with the use of any dietary supplement, probiotics, calcium, and multivitamin/mineral supplements (P < 0.001).
Infants whose mothers had used supplements during pregnancy were more likely to be given any supplement, probiotic, calcium, and multivitamin/mineral supplements, than were infants whose mothers did not (OR 1.74, 1.90, 1.72, and 1.73, respectively). Compared with infants still breast-fed at 6 months, infants who were ever breast-fed and infants fed formula were approximately 2 to 3 times more likely to be given any dietary supplements, probiotic, calcium and multivitamin/mineral supplements. The allergy status of infants was not a significant factor when predicting the use of supplements. Infants with a family history of allergies were more likely to be given a dietary or probiotic supplement than those without (OR 1.16 and 1.20, respectively).
The present research assessed the intake of nutrient-containing dietary supplements and probiotics by infants in the Taiwan Birth Cohort Study. Until recently, few studies have investigated the intake of dietary supplement by infants, particularly during their first 6 months. In the present population-based survey, approximately one-third of Taiwanese infants received supplements during their first 6 months. The Feeding Infants and Toddlers Study reported that in the United States, 8% of 4- to 5-month-old infants and 19% of 6- to 11-month-old infants received dietary supplements (4). In addition, Picciano et al (5) reported that 12% of infants younger than 1 year of age had received nutritional supplements. The higher prevalence supplement intake found in the present Taiwanese study, as compared with other studies, may be due to the longer duration of our study period. Most previous studies have surveyed the intake of supplements by infants during a period of 1 week. In the present study, we asked Taiwanese parents to report the intake of dietary supplements by their infants during the first 6 months of their lives. Furthermore, the administration of supplements to infants was predicated on the previous habits of the mothers regarding the use of supplements, infant feeding practices, and the family history of allergies. Mothers who used supplements during pregnancy were more likely to provide their infants with supplements than mothers who did not. This observation confirmed previous reports from the United States (13) and Japan (14), indicating the effect of parental history on the use of supplements.
In the present study, the groups of infants who were no longer breast-fed after 6 months and those who received complementary foods earlier than 6 months had a higher consumption of dietary supplements. A discrepancy existed between our study and a previous work. A survey on young white American children indicated that the use of dietary supplements was higher among breast-fed infants than among non–breast-fed infants (15). It is likely that the parents of the non–breast-fed infants in the United States used infant formula enriched with vitamins and minerals (16). Recently, public attention regarding the importance of breast-feeding has been increasing in Taiwan. Although most mothers recognize that breast-feeding is the best feeding method for their infants, only 22.1% of the population still breast-feeds at or beyond 6 months. Parents who do not follow the WHO recommendations for infant feeding may simply wish to give their infants what they consider to be good for them. In developed countries, during the first 2 years of life, most young children who are not breast-fed can obtain an adequate supply of most vitamins and minerals from diet alone (15). Although exposure to sunlight to obtain vitamin D may be enough for infants and children in Taiwan, it is worth noticing that infant vitamin D supplementation has been recommended by health professionals, as vitamin D deficiency remains common among infants and children (17,18). Little data are available related to the clinical effectiveness or safety of dietary supplements in infants and children; therefore, we suggest that parents exercise caution when giving their infants dietary supplements. Before providing dietary supplements for infants, parents should communicate with health professionals, such as pediatric doctors or dietitians.
Probiotics were the most common supplements given to infants in the present study, which associated family history of allergies, but not the allergic status of infants, with higher rates of probiotic use. These findings suggest that parents provide their infants probiotics for prophylactic purposes. It is worth noting that 2 randomized, double-blind, placebo-controlled studies have reported that the use of probiotic bacteria carries no risk, even when administered to extremely young infants during a long period (19,20). However, the benefit of probiotics in reducing allergies or atopic diseases is still debated. More research is required regarding the effectiveness of probiotics for the prevention of allergies (21–23). The use of formula was associated with higher use of probiotics in infants. Studies found that longer breast-feeding duration was associated with lower rates of allergies (24–26). Rather than administering probiotics to infants, prolonging the breast-feeding period is preferable.
Calcium was the second most commonly used type of supplement in the present study. Calcium was also reported to be a popular supplement for older children in Germany (27) and Taiwan (3) but has not commonly been given to infants in other studies (4,5,15). In Taiwan, insufficient calcium intake has been reported among several age groups (28–30), which may in part explain the popularity of calcium supplements for Taiwanese infants and children. However, another survey found that most Taiwanese children between 1 and 3 years old have sufficient calcium intake (31). The results of studies related to calcium deficiency in industrialized countries remain inconclusive; therefore, we recommend considering in greater detail the risks of high dosages of calcium supplements for infants. Our study suggests that infants who were ever breast-fed or formula-fed were more likely to receive calcium supplements. The optimal source of calcium for infants is human milk. The bioavailability of calcium from human milk is greater than that of infant formula (32). Thus, the concentration of calcium in infant formula is higher than that in human milk, thereby ensuring comparable levels of calcium retention. Based on this information, parents should be reminded of the differences between human milk and formula, and that offering calcium supplements to formula-fed infants may increase the physical load of excreting excessive calcium.
Multivitamin/mineral supplements are the most commonly used dietary supplements among all of the pediatric age groups (27,33,34) and the third most common in the present study. Parents with a history of allergies were more likely to give their infants multivitamin/mineral supplements, although the data did not indicate any clear reason for this. A previous study associated early vitamin supplementation with an increase in the risk of asthma and food allergies in children (35). Several reports have emphasized that food, not supplements, provides the necessary nutrients for the growth and development of healthy infants and children, particularly regarding the absence of evidence-based standards for the use of supplements in infants and children (4,36,37).
The main limitation of the present study was the lack of data concerning specific dosages and the frequency of the use of supplements during the 6-month study period. Only categories of dietary supplements were analyzed. However, the Nutrition and Health Survey in Taiwan Elementary School Children (2001–2002) found that approximately 45% of children who used dietary supplements did so regularly (3). Additionally, the present study only examined the duration of breast-feeding and the time of complementary feeding. Data related to infant nutrient intake were not available for analysis. Furthermore, it should be noted that the results of the present study apply only to full-term, normal-birth-weight infants in Taiwan. Whether the same relationship would be observed in other infants is uncertain. Finally, the reasons for parents giving their infants dietary supplements were not collected in the present study. Baker (38) noted that parents give their children dietary supplements to be good parents, to control health, and as a substitute for good nutrition; but misguided parents may in fact poison their children. Parents who provide their infants with dietary supplements may not understand the differences among breast milk-, infant formula-, and complementary feeding. Further studies are required to clarify the reason for parents giving their children dietary supplements.
Our findings confirm that the pediatric use of dietary supplements in Taiwanese infants is relatively common, even in the earliest stages of life. Formula feeding, earlier weaning, and earlier complementary feeding were positively related to the use of supplements. When a normal diet is adequate for infants, no need exists for dietary supplements; furthermore, excessive supplement intake could adversely influence health. Communication between health professionals and child caregivers should be promoted to enhance understanding of infant feeding, as well as the safety and efficacy of dietary supplements.
For their enduring support and assistance, we thank Professor Tung-Liang Chiang, Institute of Health Policy and Management, National Taiwan University College of Public Health, Taipei, Taiwan; Professor Meng-Chin Lee, Institute of Medicine, and Professor Hui-Sheng Lin, School of Public Health, Chung Shan Medical University, Taichung, Taiwan; and Professor Bih-Ching Shu, Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
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