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What is Vitamin D?

    By Cynthia Sears, MS, BC

    Did you know that “Vitamin D” is not really a vitamin? It’s actually a steroid hormone produced in the body after direct exposure of the skin to ultraviolet B (UVB) radiation in sunlight. Both the vitamin D that your body produces and the vitamin D from supplements must be changed by your body several times before it can function properly. Vitamin D manages the amount of calcium in your blood and other body tissues, helps cells all over your body communicate properly, and assists your immune system in functioning effectively (Vitamin D Council, 2013).

    What are the consequences of Vitamin D Deficiency?
    Vitamin D deficiency may present with seizures due to abnormally low calcium levels, growth failure/failure to thrive, lethargy, irritability, and a predisposition to respiratory infections during infancy (Balasubramanian, 2011). In extreme cases, vitamin D deficiency can result in the development of rickets, a childhood bone disorder where bones soften and become prone to fractures and deformity.

    If you have older children and are wondering why this wasn’t an issue when they were babies, the American Academy of Pediatrics (AAP) recently updated its vitamin D recommendations based on research that was published in April of 2010; it took a few years for the policy change to take full effect.

    Nutritional Recommendations for Vitamin D
    The AAP recommends supplementation of vitamin D for all infants as a preventive health measure. The AAP recommends that all children, including infants, take in 400 international units (IU) of vitamin D per day. Infants 0-12 months should not exceed 1,000 IU (25 µg) per day. Recommendations for adult intake vary depending on the organization, but usually advise an upper limit of 5000 – 10000 IU/day.

    To Supplement or not?
    Exposure to natural sunlight allows the human body to make its own vitamin D. The amount of the vitamin produced, however, is dependent on a variety of factors. Cynthia Good Mojab, MS, IBCLC, RLC writes, “The amount of sunlight exposure needed to prevent vitamin D deficiency depends on such factors as skin pigmentation, latitude, degree of skin exposure, season, time of day, amount of pollution, degree of use of sunscreen, altitude, weather, the vitamin D status of the lactating mother, and the current status of vitamin D stores in the infant’s body. Recommendations do and should, therefore, vary around the world, taking into account local conditions and practices.” (Mojab, 2003).

    The World Health Organization recommends two hours per week of direct sunlight exposure for infants when the face is the only part of the body exposed, or 30 minutes if upper and lower extremities are exposed. But remember that the factors listed above must also be considered. Due to increases in skin cancer rates, often due to sun exposure and/or tanning beds, many healthcare professionals would prefer that unprotected sun exposure be kept to a minimum. Consequently, sunlight exposure recommendations are not hard and fast rules.

    The decision on whether or not vitamin D supplementation is necessary for your child can and should be made in conjunction with your child’s health care provider. The most important thing is to make an informed decision, feeling comfortable bringing up your own questions and concerns, and sharing your informed perspective. A blood test (the 25-Hydroxy Vitamin D test) can assess your child’s existing levels of vitamin D (NIH-NLM, 2012).

    Breastfeeding and Vitamin D
    When breastfeeding exclusively, a mother’s pre-existing deficiency in vitamin D can result in lower levels of vitamin D in the milk she produces. If her baby gets enough sunlight, the mother’s deficiency is unlikely to be a problem for her baby. However, if her baby is not producing enough vitamin D from sunlight exposure, her milk will need to meet a larger percentage of her baby’s vitamin D needs.

    The Vitamin D Council advises mothers to choose to either supplement their infant with vitamin D drops, or take a high-dose supplement of vitamin D themselves when exclusively breastfeeding (Vitamin D Council, 2013). Maternal supplementation of 6,000 IU of vitamin D per day would prevent the need for infant supplementation; the milk would likely have enough vitamin D for baby (Wagner et al., 2006). If the mother is not taking a supplement, getting a good amount of sun exposure, or taking less than 5,000 IU per day of vitamin D, her baby might need a vitamin D supplement. Mothers who choose high-dose maternal vitamin D supplementation should consider getting their vitamin D levels tested to see if supplementation is needed. Mother and baby could then be tested a few months later to track the levels.

    Optimal vitamin D levels and the impact of deficiency on the body are the subjects of ongoing studies. For mothers, the prevention of rickets and other known effects of deficiency in babies is the main concern. How this is accomplished should be decided by parents making an informed choice based on available information and discussion with the mother and baby’s health care providers.


    AAP. (2010). Vitamin D Supplementation for Infants. Retrieved on February 23, 2014

    Balasubramanian, S. (2011). Vitamin D deficiency in breastfed infants & the need for routine vitamin D supplementation. The Indian Journal of Medical Research, 133(3), 250–252. Retrieved on February 23, 2014

    Cannell, J. (2009). Newsletter: Vitamin D Question & Answers. Retrieved on March 3, 2015

    Mojab, C. G. (2003). Frequently asked questions about Vitamin D, Sunlight, and Breastfeeding. Retrieved on February 23, 2014

    NIH National Library of Medicine. (2012). 25-Hydroxy Vitamin D Test. Retrieved on February 23, 2014

    Vitamin D Council. (2013). Vitamin D supplementation for pregnant and breastfeeding mothers. Retrieved on February 23, 2014

    Wagner, C. L., Hulsey, T. C., Fanning, D., Ebeling, M., & Hollis, B. W. (2006). High-dose vitamin D3 supplementation in a cohort of breastfeeding mothers and their infants: a 6-month follow-up pilot study. Breastfeeding Medicine, 1(2), 59-70. Retrieved on February 23, 2014

    Cynthia Sears, MS, BC

    Cynthia Sears is a doctoral student in Health Education and Behavior at the University of Florida and one of the founding members of the North Central Florida chapter of Breastfeeding USA. She is the mother of two breastfed sons.

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