Surely I can just let my daughter’s chubby little baby legs stick out in the sunshine once in a while? It’s not that simple.

As the mother of a young infant, I visit the pediatrician too often. Every visit the nurses and doctor repeat the same questions: “How is she eating? How are her bowel movements? And of course, are you still breastfeeding?” “Good, good, and yes!” I am always proud to respond (I breastfed my eldest until she was two years and four months old). At least that I’ve got right, I think. But then they ask “Are you giving her vitamin D supplements?” This question is harder to answer because the truth is “Sure, like twice.” Formula already contains the recommended vitamin D supplement, so parents of formula-fed infants don’t get asked this question. The doctor explains that vitamin D is important for healthy bone development and many other bodily processes, and that babies might not see enough sun to produce the vitamin on their own. But we live in Saudi Arabia (and before that, the mid-Atlantic region of America) where there is a lot of sun. Why would we need vitamin D supplements?

In a vitamin-D utopia, we breastfeeding mothers would run around outside, babies in kangaroo carriers, absorbing solar rays with our arms spread wide open in a sun salutation just long enough to create sufficient vitamin D (but not a moment longer, or we’d risk skin cancer). A perfectly adequate amount of UVB from the golden sunshine would touch the provitamin D3 in our skin, transforming it first to previtamin D3 and then (via a reaction with a catalyzing agent called 7-dehydrocholesterol inside the skin cells) to vitamin D3. Flowing through our veins into the liver, this vitamin D3 would become 25-hydroxyvitamin D (25OHD), which is the marker used by doctors and scientists to evaluate vitamin D absorption.

Unfortunately, many things interfere with our access to the sun, such as indoor office jobs and valid skin cancer fears. It is also incredibly difficult to get enough of this vitamin from diet alone. Very few foods contain it naturally, and if you’re vegan or vegetarian, the options are especially limited (I hope you like UV-treated mushrooms) since the main food source is oily fish. For this reason, doctors recommend oral supplements. After a quick search for images of “rickets,” I decided to follow their recommendations.

But how is the power of the sun harnessed in a bottle? Some plants and animals also produce vitamin D. There are two kinds of vitamin D supplements: vitamin D2 “ergocalciferol” (vegan; fungus/yeast-derived product) and vitamin D3 “cholecalciferol” (not vegan; derived from lanoli – the oil from sheep’s wool – or fish oil). Lichen-derived (i.e., vegan) vitamin D3 is also available, but I could only find two producers (https://www.nutrasciencelabs.com/; https://www.vitabay.net/) and it is much more expensive than the alternatives. For these reasons, vitamin D2 from UV-treated mushrooms and yeast is commonly used in fortified foods. However, peer-reviewed studies show that it is less readily absorbed by the human body than vitamin D3.

Great, so I know I need to buy a vitamin D3 supplement. But for whom? An infant can receive sufficient vitamin D from breastmilk if the mother takes a large enough amount of vitamin D supplements. However, the amount of supplement required (6400 IU) far exceeds the daily allowance (600 IU) and maximum intake (4000 IU) recommended for lactating mothers by the National Institutes of Health. For my family, we’ve decided that we both should take a moderate supplement – 400 IU for the baby, 1000 IU for me – and an occasional afternoon walk in the sun.

Sources

1. Centers for Disease Control and Prevention. (2018). Breastfeeding: Vitamin D. Retrieved from https://www.cdc.gov/breastfeeding/breastfeeding-special-circumstances/diet-and-micronutrients/vitamin-d.html
2. Centers for Disease Control and Prevention. (2018). Infant and Toddler Nutrition: Vitamin D. Retrieved from https://www.cdc.gov/nutrition/infantandtoddlernutrition/vitamins-minerals/vitamin-d.html
3. National Institutes of Health, Office of Dietary Supplements. (2018). Vitamin D
   Fact Sheet for Health Professionals. Retrieved from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
4. Wagner, C.L., & Greer, F.R. (2008). Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents. Pediatrics, 122 (5) 1142-1152; DOI: 10.1542/peds.2008-1862. Retrieved from http://pediatrics.aappublications.org/content/122/5/1142.long
5. American Academy of Pediatrics. (2011). AAP Recommendations on Limiting Sun Exposure in Children and Supporting Legislation to Prohibit Salon Tanning by Minors. Retrieved from https://www.aap.org/en-us/about-the-aap/aap-press-room/pages/AAP-Recommendations-on-Limiting-Sun-Exposure-in-Children-and-Supporting-Legislation-to-Prohibit-Salon-Tanning-by-Minors.aspx
6. Norman, A.W. (2008). From vitamin D to hormone D: Fundamentals of the vitamin D endocrine system essential for good health. The American Journal of Clinical Nutrition. Volume 88, Issue 2, Pages 491S–499S, https://doi.org/10.1093/ajcn/88.2.491S. Retrieved from https://academic.oup.com/ajcn/article/88/2/491S/4649916
7. Wacker, M., & Holick, M. F. (2013). Sunlight and Vitamin D: A global perspective for health. Dermato-endocrinology, 5(1), 51-108. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897598/
8. Tian, X.Q., Chen, T.C., Matsuoka, L.Y., Wortsman, J., & Holick, M.F. (1993). Kinetic and thermodynamic studies of the conversion of previtamin D3 to vitamin D3 in human skin. The Journal of Biological Chemistry, 268, 14888-14892. Retrieved from http://www.jbc.org/content/268/20/14888.long
9. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross A.C., Taylor C.L., Yaktine A.L., et al., editors. (2011). Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US). Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK56056/#ch5.s17
10. Esposito, L., & Kotz, D. (2018). How Much Time in the Sun Do You Need for Vitamin D?. U.S. News. Retrieved from https://health.usnews.com/wellness/articles/2018-07-18/how-much-time-in-the-sun-do-you-need-for-vitamin-d
11. United States Department of Agriculture, Agricultural Research Service. USDA Food Composition Databases. Retrieved from https://ndb.nal.usda.gov/ndb/nutrients/report?nutrient1=324&nutrient2=&nutrient3=&fg=&max=25&subset=0&offset=0&sort=c&totCount=5425&measureby=m
12. Toyn, C., Darling, A., Hart, K., Tripkovic, L., Smith, C., Mathers, J., & Elliott, R. (2018). Effect of vitamin d2 supplementation on serum 25 hydroxy-vitamin d3 levels: A systematic review and meta-analysis. Proceedings of the Nutrition Society, 77(OCE1), E12. doi:10.1017/S0029665117004311. Retrieved from https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/effect-of-vitamin-d2-supplementation-on-serum-25-hydroxyvitamin-d3-levels-a-systematic-review-and-metaanalysis/C3489970DF534383A3C1EC5318016B0D
13. Hinde, N. (2018). Why Is There Sheep’s Wool Grease In My Cereal? HuffPost UK. Retrieved from https://www.huffingtonpost.co.uk/entry/why-is-there-sheeps-wool-grease-in-my-cereal_uk_5af2b69de4b00a3224eeb1e3?guccounter=1&guce_referrer_us=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_cs=k2HhxcgYclrWp9RNC1Ot4g
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    Pediatrics, 136 (4) 625-634; DOI: 10.1542/peds.2015-1669
    http://pediatrics.aappublications.org/content/early/2015/09/22/peds.2015-1669.abstract