Enamel Development and Vitamin D Deficiency in Breastfed Infants

Breastfeeding within the first year of life is encouraged because it decreases health risks and provides nutritional benefits for the infant and mother. The American Academy of Pediatrics (AAP) recommends “exclusive breastfeeding for six months, followed by continued breastfeeding as complementary foods are introduced, with continuation of breastfeeding for one year or longer as mutually desired by mother and infant.”¹ Among children born in 2016, 47.5% were exclusively breastfed for three months, and 25% were exclusively breastfed until six months.² While breastfeeding exclusively is recommended for infants and provides a higher intake of nutrients than other feeding practices, the vitamin D concentration in breast milk is usually insufficient to meet the infant’s needs.³ For example, very low concentration of vitamin D (approximately 10 to 80 IU/L) passes into human breast milk, which reflects 1.5% to 3% of the maternal level (Figure 1); this may contribute to vitamin D deficiency in the infant.^4–8 This paper will describe the relationship between vitamin D deficiency and enamel development, provide national supplementation recommendations for mothers and children, and discuss the role of dental professionals in promoting oral health among these patients.

Among U.S. women of childbearing age (20 to 44 years), a national study revealed 10% to 12% are vitamin D deficient, and 25% to 27% have inadequate levels of vitamin D.⁹ A high prevalence of maternal deficiency persists, despite the daily intake of prenatal vitamins containing 400 IU vitamin D.⁵ However, providing vitamin D-deficient pregnant and lactating women with supplements containing high concentrations of vitamin D (1000 to 2000 IU, and up to 4000 IU in latter cases) is thought to be safe.¹⁰ Deficiencies typically present when intake is lower than recommended levels — 25‐hydroxyvitamin D [25(OH)D] ≤ 30 to ≤ 50 nanomoles per liter (nmol/L) — over time (Table 1). Vitamin D deficiency is common across all age groups.¹¹ Contributing factors include limited sunlight exposure and restricted diets due to allergies or intolerance (e.g., dairy), veganism, or impaired absorption (e.g., digestive disorders).¹² According to the National Institutes of Health, serum vitamin D levels ≥ 50 nmol/L in all populations is considered adequate for bone and general health.¹³

Inadequate levels of vitamin D during rapid phases of enamel formation (in utero for primary dentition, and postnatal for permanent dentition) increase the risk of interruptions in the enamel matrix, which can lead to defects, such as enamel hypoplasia.¹⁴ These enamel defects increase susceptibility to caries, a process that is led by Streptococcus mutans bacteria colonized within dental plaque.¹⁵ Within this plaque, bacteria can easily adhere to a defective enamel surface, creating an environment prime for lesion development.^14,16 Dental caries is considered the most common preventable chronic disease of childhood, with 21.4% of children under the age of five experiencing disease.¹⁷ The literature suggests a relationship between low vitamin D levels during the prenatal period and caries in the primary dentition.^18,19 In addition, developmental defects — including enamel hypoplasia — have been associated with caries in the primary dentition.^14,18 While caries is a multifactorial process, vitamin D-deficient infants have a greater risk for developing enamel defects, thus increasing caries risk.

Given the relationship between vitamin D and enamel development, it is important for dental professionals to provide expectant mothers and caregivers with the resources needed to minimize the risk of vitamin D deficiency in infants who will be exclusively breastfed.

Enamel Development

Maternal concentrations of vitamin D directly relate to the recommended 25(OH)D serum level available to transfer to human breast milk. Infants who are exclusively breastfed by women with vitamin D intake of 400 IU/day (standard prenatal vitamin quantity) typically attain a circulating 25(OH)D concentration in the “marginally sufficient” to “severely deficient” (< 12.5 nmol/L) range.²⁰

Vitamin D plays a critical role in enamel, dentin and oral bone formation, as ameloblasts and odontoblasts are target cells for 1,25-dihydroxyvitamin D, the active form of vitamin D.²¹ Adequate amounts of vitamin D during rapid phases of tooth development can prevent enamel defects, such as hypocalcification, which is also associated with caries.^14,18,22,23 An enamel surface with compromised mineralization, porosity and irregularities is a predisposing risk for plaque accumulation. Defective enamel (e.g., pitting, grooves or irregularities, including hypoplasia) increases the risk of early colonization by cariogenic bacteria, resulting in caries.¹⁸ There is an increased risk of developing enamel defects in a vitamin D-deficient environment.

The most recent revision of the caries risk assessment form includes enamel defects as a risk factor in both pediatric age groups (0 to age 5, and 6 and older), and places children with defects into a high-risk category.^24,25 This risk assessment tool can be useful for oral health education and anticipatory guidance with the caregiver and child during the initial and subsequent dental visits. When moderate- to high-risk factors are identified at a young age, early interventions can be discussed and implemented to reduce caries risk (Table 2).^24,25

Vitamin D Supplementation

Infants born to vitamin D-deficient mothers are often vitamin D deficient at birth and have a greater risk for developing enamel hypoplasia.^{18,19,26–29} Thus, adequate maternal vitamin D levels during the last trimester of pregnancy are essential in establishing the infant’s vitamin D reserves.^10–30 These stored levels of 25(OH)D are depleted in the neonate within six to eight weeks postpartum, and the infant must depend solely on vitamin D from external sources, such as supplementation.^22,31 Vitamin D supplementation during enamel development is essential for infants who are identified as vitamin-D deficient. To reduce the risk of vitamin D deficiency, the AAP recommend all children who are breastfed, or consume less than 1 liter of formula per day, receive vitamin D supplements (400 IU/day) beginning in the first few days of life through the first year.³² From 2009 to 2012, less than one in five U.S. breastfed infants age 0 to 11 months met the AAP recommendations of 400 IU/day of vitamin D supplementation. Among this group, a supplement medicament was the most common form of consumption other than the use of formula.³³ In general, supplementation should continue until the infant receives a minimum of 1 liter per day of vitamin D-fortified formula or whole milk.^34,35 Supplementing exclusively breastfed infants daily with 400 IU of vitamin D provides consistent serum concentrations of 25(OH)D at ≥ 50 nmol/L.³⁶ Oral supplementation options for infants in the U.S. are dispensable in the form of liquid drops or milliliter dosing, and are prepared at 400 IU/day.²³ Caregivers should be encouraged to utilize the manufacturer provided dispenser and follow dosing instructions.^23,35 The use of oral supplementations can be integrated during diaper changes, bottle preparations, or any daily routine that can be easily adopted by the caregiver.

Dental Professionals’ Role

With more than 80% of new mothers attempting to breastfeed,² dental professionals are in a unique position to provide oral health education to expectant mothers and caregivers during the first six to 12 months postpartum. While prenatal providers and pediatricians are the primary prescribers of vitamin D treatment regimens, it is important for dental teams to be current with vitamin D supplementation recommendations. Understanding the pathways and etiologies leading to developmental defects in the enamel — which may increase caries susceptibility — is essential.

In addition to interactions within the dental office, in 38 states dental hygienists have expanded functions that include providing services in medical settings, federally funded centers, public health offices, community health centers, and clinics.³⁷ The inclusion of preventive dental services and oral health education in these diverse settings provides an opportunity to engage pregnant and postpartum women, caregivers and infants. In addition, alternative practice settings allow for interprofessional collaborative practice with primary care and prenatal providers who provide health services to women and children. Dental professionals can promote vitamin D supplementation for mothers and children by:

• Working collaboratively with pediatricians, prenatal and primary care physicians to provide current, evidence-based information on the implications of breast milk and vitamin D deficiency
• Staying current with evidence-based supplementation recommendations
• Providing educational materials/information about the benefits of vitamin D supplementation and the effects on oral health

Conclusion

Among health care providers, the relationship between breastfeeding exclusively and vitamin D deficiency in infants requires a collaborative approach and ongoing conversations during prenatal and postnatal care. Early interventions — such as prescribing vitamin D supplements and recognizing risk factors for caries — are essential to promoting positive oral and overall health outcomes for the infant.

References

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From Decisions in Dentistry. December 2020;6(11): 32-35.