Vitamin D is an essential nutrient that can be synthesized in the skin with exposure to sunlight or obtained from plant (vitamin D2) and animal (vitamin D3) food sources. Vitamin D plays essential roles in bone and musculoskeletal development and is implicated in other health outcomes such as blood pressure, immunity, mood, and more.

Data suggests that vitamin D deficiency is a significant health issue for people of all ages. However, infants are particularly vulnerable to vitamin D deficiency. Understanding more about the impacts of vitamin D on infant health can help caregivers take the necessary steps to ensure their little ones receive adequate amounts of this vital nutrient, enough to keep them at healthy blood levels.

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This article will explore vitamin D deficiency, its impact on infant health, and ways to support infants in meeting their vitamin D needs.

 

Definition and Prevalence of Vitamin D Deficiency

The best indicator of vitamin D status is serum 25(OH)D levels, which can be measured with at-home nutrient test kits or with a healthcare provider. However, some controversy exists around definitions of vitamin D deficiency clinical cut-off points.

For example, the Institute of Medicine (IOM) considers vitamin D deficiency to be 25(OH)D levels <30 nmol/L, insufficiency between 30-50 nmol/L, and sufficiency ≥50 nmol/L. Yet the Endocrine Society cites the cut-off value for vitamin D deficiency as <50 nmol/L, insufficiency at 50-70 nmol/L, and sufficiency as ≥70 nmol/L.

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Furthermore, the current data on vitamin D deficiency prevalence may be incomplete due to discrepancies in clinical cut-off points and missing data for many low- and middle-income countries. Nevertheless, vitamin D deficiency is considered a global health concern, and monitoring individual levels may be important, especially for those groups at greater risk of vitamin D deficiency.

 

Groups at Risk for Vitamin D Deficiency

One of the most important determinants of vitamin D status is the amount of vitamin D the skin can produce through UVB exposure. Therefore, those who don’t get adequate sun exposure from spending too much time indoors, use sunscreen or protective clothing, have darker skin tones, or live in geographic locations where UVB light is limited are at great risk for vitamin D deficiency.

Aging can also increase the risk for vitamin D deficiency since aging decreases the capacity of the skin to produce vitamin D. Furthermore, evidence indicates that social determinants such as marital status, educational attainment, and family income-to-poverty ratio may influence the risk for vitamin D deficiency, where lower socioeconomic status increases risk.

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Finally, infants are particularly vulnerable to vitamin D deficiency, as their vitamin D status primarily depends on the status of their mother, the vitamin D content of the milk or formula they are consuming, and whether they receive vitamin D supplementation.

The prevalence of infant vitamin D deficiency may vary wildly around the globe, but within the US, a 2008 study on infants and toddlers aged between 8 and 24 months found that 12.1% were deficient (<50 nmol/L), and 40% were insufficient (<70nmol/L) in vitamin D.

Evidence shows a cumulative risk for infants that increases in a dose-response depending on the number of risk factors. Some additional risk factors that can accumulate include being breastfed only, being a girl, having a multiparous mother, and using sunscreen.

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Risks of Vitamin D Deficiency on Infants’ Health

According to a recent review (Oct 2023) investigating the impact of vitamin D deficiency on the health of infants, the most common effects of vitamin D deficiency are related to bone and musculoskeletal health – represented by rickets in children.

Nutritional rickets is a bone disorder caused by low vitamin D status and dietary calcium intake. It may manifest as impaired linear growth, chest wall deformity, bone pain and fractures, leg deformities, and developmental delay of gross motor skills. Vitamin D deficiency occurs months before the symptoms of rickets become evident on physical examination. Therefore, monitoring vitamin D status regularly throughout an infant’s and child’s growth and development may provide opportunities to correct vitamin D deficiency before symptoms develop.

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According to the report, due to downstream effects on calcium levels, infant vitamin D deficiency can also lead to seizures, growth failure, irritability, lethargy, and muscle weakness. Likewise, vitamin D’s downstream effects on immunity affect infant and child respiratory health. Studies report a significant association between low vitamin D status in newborns and the risk of developing a lower respiratory tract infection, with a sixfold increased risk of lower respiratory tract infections in newborns with vitamin D levels <50mol/L compared to those >75nmol/L.

Furthermore, maternal monitoring of vitamin D appears necessary, as vitamin D deficiency in pregnant women can also impact infant health outcomes. In early pregnancy, 25(OH)D crosses the placenta from mother to fetus and appears to be delivered to the fetus on average at 80% of the value of the mother. Therefore, if the mother is deficient, so will the fetus.

Studies report maternal vitamin D deficiency has been linked to a higher risk of preterm birth, low birth weight, lower bone mass, respiratory tract infections, asthma, and increased risk of Multiple Sclerosis in infants and children.

 

Current Vitamin D Recommendations for Infants and Children 

The Centers for Disease Control and Prevention (CDC) recommends that children younger than 12 months receive 400 IU/d of vitamin D, and children 12 to 24 months receive 600 IU/d. Furthermore, the CDC breaks out their recommendations for infants receiving breast milk versus those receiving only infant formula.

For infants fed only breast milk or who receive both breast milk and infant formula, the recommendation is to supplement infants with 400 IU/day beginning shortly after birth. The CDC states that vitamin D supplementation is unnecessary for babies receiving only infant formula (in the US) since infant formulas are already fortified with adequate vitamin D levels.

Vitamin D status checks and supplementation needs may need to continue further into adolescence to optimize growth and development. The American Academy of Pediatrics Guidelines recommend that adolescents who do not obtain 400 IU of vitamin D daily through fortified foods should receive a 400 IU/day vitamin D supplement. Furthermore, they recommend serum 25(OH)D concentrations in infants and children to be ≥ 50nmol/L (20ng/mL).

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How Can I Ensure My Infant is Getting Enough Vitamin D?

Given the inherent risks of relying on UVB light for vitamin D, the American Academy of Pediatrics recommends keeping babies younger than six months out of direct sunlight and protecting them with clothing and hats to decrease their risk of skin cancer. Furthermore, there are a limited number of foods in which vitamin D is found naturally. Therefore, fortification and supplementation are the most widely used strategies for improving vitamin D levels in infants and children.

Fortification involves adding vitamin D to widely consumed food products to increase vitamin D intake. Some of the most commonly fortified foods include milk and dairy products, breakfast cereals, and fruit juices. Baby formulas in the US are also vitamin D fortified, and the US FDA regulates commercially made infant formulas to ensure they meet minimum nutritional and safety requirements.

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Vitamin D supplementation is another reliable strategy for improving outcomes in those who are vitamin D deficient. Supplementation of either, or both, mother and infant may support infant outcomes. According to a 2015 study, maternal supplementation may require daily doses of 6400 IUs to increase vitamin D content in breast milk to reach the equivalent of 200-400 IU/day for infant consumption.

Alternatively, breastfeeding mothers and infants can be supplemented with lower doses to achieve desirable infant vitamin D status. One study found that when mothers were supplemented with 600 IU/day and infants were supplemented with 400 IU/day, infant serum 25(OH)D levels were slightly higher compared to infants receiving all of their vitamin D from the breastmilk of mothers being supplemented with 6000 IU/day.

 

Conclusion

Vitamin D is vital for bone mineralization and musculoskeletal health. Yet current evidence suggests that vitamin D deficiency is a global health issue with potentially significant implications for those at risk, such as the infant population. Although the understanding of vitamin D has improved over time, there are still knowledge gaps and disagreements among health organizations, leading to a lack of clear definitions and recommendations.

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While waiting for the scientific and clinical communities to address these gaps with further research and reliable evidence, there are some steps that can take to minimize the risk of vitamin D deficiency in infant populations. Current evidence recommends that serum 25(OH)D concentrations in infants and children be ≥ 50nmol/L (20ng/mL).

This may be accomplished by supplementing mothers with high amounts (~6000IU/d) of vitamin D daily if infants are being breastfed, by supplementing in lower doses both mother (~600IU/d) and infant (~400IU/d), or by ensuring infants and children are meeting the recommended intake through formula or fortified food. Currently, the best strategy seems to be regularly monitoring mother and infant vitamin D status to determine if vitamin D supplementation is required.

 

These statements have not been evaluated by the Food and Drug Administration. This test is not intended to diagnose, treat, cure, prevent or mitigate any disease. This site does not offer medical advice, and nothing contained herein is intended to establish a doctor/patient relationship. OmegaQuant, LLC is regulated under the Clinical Laboratory improvement Amendments of 1988 (CLIA) and is qualified to perform high complexity clinical testing. The performance characteristics of this test were determined by OmegaQuant, LLC. It has not been cleared or approved by the U.S. Food and Drug Administration.

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