About vitamin D

Why does vitamin D matter?

Vitamin D is an essential nutrient for human health and development, helping with absorption of calcium in particular, and also phosphorous, from food passing through the gut. Insufficient vitamin D can reduce calcium absorption by up to 50%. Severe vitamin D deficiency in infancy and childhood results in

• Nutritional rickets including leg deformities, delayed closure of the fontanelles, weakness of the bones, and delayed dental eruption or caries

• Increased propensity for respiratory infections

• Cardiovascular problems.

Symptomatic vitamin D deficiency in childhood is a re-emerging global problem.

During pregnancy, physiological adaptations occur to meet the fetal demand for calcium, with 80% of this accumulated during the third trimester. These adaptations, including a doubling of maternal intestinal calcium absorption, are dependent on adequate maternal vitamin D status.

Global consensus recommends that pregnant women receive 600-1000 IU/day of supplemental vitamin D. This level of antenatal supplementation has been shown to increase childhood bone density at four and six to seven years of age.

Why is it important to detect vitamin D deficiency in pregnancy?

Up to 40% of Australian pregnant women may be vitamin D deficient, depending upon season and ethnicity. A global consensus defines levels as:

• Deficiency: <30nmol/l

• Insufficiency: 30-50nmol/l

• Sufficiency: >50nmol/l.

Maternal vitamin D deficiency has been linked (though not necessarily causatively) with

• Pre-eclampsia

• Gestational Diabetes Mellitus

• Other complications such as increased rates of caesarean section, bacterial vaginosis, and pregnancy loss.

Where does vitamin D come from?

Vitamin D is obtained from

• Dietary sources (although foods and drinks including breast milk are not a major source)

  • Fatty fish (salmon, tuna, sardines) egg yolk, cereals

  • Egg yolk, full-fat cheeses, butter, cereals

  • Some mushrooms contain good amounts of vitamin D.

• Sunlight exposure. Humans synthesise vitamin D in the skin through exposure to UVB rays, which convert endogenous cholesterol into its active form through hydroxylation reactions in the liver and kidneys.

Meeting the vitamin D needs of a breastfed infant

Low vitamin D, in combination with low calcium or low phosphate, can lead to nutritional rickets but this is rare in breastfed infants. Breast milk and casual sunlight exposure are generally sufficient to meet a breastfeeding infant's vitamin D requirements.

Exclusively breastfed babies are at increased risk of vitamin D deficiency if their mother has

1. Vitamin D deficiency, either in pregnancy or current, or

2. One or more risk factors for vitamin D deficiency such as

   • Veiling

   • Predominantly spending the days indoors

   • Darker skin tone

   • Limited sun exposure, including by living in northernmost or southernmost latitudes

   • Higher body fat (which alters vitamin metabolism)

   • Various medical conditions (kidney disease, liver disease, cystic fibrosis, preterm birth).

In these cases, the Australian National Health and Medical Research Council (2012) advises 400 IU daily supplementation for these babies from birth, without requiring a blood test. This is administered by a liquid preparation purchased without a script from the pharmacy, on a spoon. However, maternal supplementation with 6000 IU/day of vitamin D3 can achieve adequate maternal and infant serum 25(OH)D levels in the exclusively breastfeeding pair and may be more acceptable to families than infant supplementation.

The amount of vitamin D in commercial milk formulas is variable. Vitamin D drops can be added to formula if the baby is receiving formula.

The Australian Breastfeeding Association notes that when the UV levels are below 3, a few minutes of direct UV exposure without sun protection is safe for babies. You can find out more about this here. Active play outside or time spent outside is encouraged for all babies and children, using sun protection that is appropriate for the UV levels.

Meeting the vitamin D needs of a breastfeeding woman

Although maternal vitamin D requirements are not elevated during lactation, maternal vitamin D deficiency is common worldwide.

Vitamin D deficiency is a public health issue (25-hydroxyvitamin D below 20 ng/ml) for all children and adults in many countries generally, and pregnant women are at an expecially high risk. Maternal vitamin D deficiency in pregnancy may increase the risk of preeclampsia, preterm birth, small-for-gestational-age onfants, intrauterine growth restriction, and gestational diabetes.

A high prevalence of vitamin D deficiency has been reported in breastfeeding women from different countries (Mexico: 62%, United Arab Emirates: 61%, China: 52%, India: 48%, Turkey: 46%). Low sun exposure and low dietary intake are the main factors associated with low serum vitamin D concentrations.

Globally, the recommended intake of vitamin D during lactation range from 200 to 600 IU/day. An upper tolerable intake of vitamin D has been set at 4,000 IU/day. However, this number has been controversial, because doses of even up to 10,000 IU/day are not related to toxicity. The US Endocrine Society recommends a daily dose of 1,500–2,000 IU/day for breastfeeding mothers to meet their own needs but states that women may need 4,000–6,000 IU/day to meet the needs of their infants.

A recent review of vitamin D supplementation in breastfeeding women (6 studies) showed that most infants (90%) in the group supplemented with ≥4,000 IU/day had adequate vitamin D status.

Vitamin D intake may alter the amount found in a mother's breastmilk, but there are no clear guidelines for the dose required to increase breast milk concentrations. Infant vitamin D is primarily received from sun exposure. If the breastfeeding mother continues to have, or has had, low vitamin D levels (less than 50 nmol/l), her infant requires supplementation, as detailed above.

Selected references

Abe SK, Balogun OO, Ota E, Takahashi K, Mori R. Supplementation with multiple micronutrients for breastfeeding women for improving outcomes for the mother and baby. Cochrane Database Syst Rev. 2016;2(2):CD010647. https:/doi.org/10.1002/14651858.CD010647.pub2

Billich, N. "Hungry bones: the importance of vitamin D for mothers and their babies", unspecified date, Australian Breastfeeding Association.

Australian Government Department of Health and Aged Care. (2020). Australian Pregnancy Care Guidelines. https://app.magicapp.org/?language=bi#/guideline/jm83RE

Bando, Nicole. "Breastfeeding: when vitamin and mineral supplementation is required", Australian Breastfeeding Association Factshee for Health Professionals. Date unknown.

Curtis EM, Moon RJ, D'Angelo S. Pregnancy vitamin D supplementation and childhood bone mass at age 4 years: findings from the Maternal Vitamin D Osteoporosis Study (MAVIDOS) randomized controlled trial. JBRM Plus. 2022;6(7):e10651.

Dawodu A, Salameh KM, Al-Janahi NS, Bener A, Elkum N. The effect of high-dose postpartum maternal vitamin D supplementation alone compared with maternal plus infant vitamin D supplementation in breastfeeding infants in a high-risk population. A randomized controlled trial. Nutrients. 2019;11(7):1632.

Favara G, Maugeri A, Barchitta M. Maternal lifestyle factors affecting breast milk composition and infant health: a systematic review. Nutrients. 2025;17(62):https://doi.org/10.3390/nu17010062.

Jimenez MPH, De la Calle S, Vives CC, Saez DE. Nutritional supplementation in pregnant, lactating women and young children following a plant-based diet: a narrative review of the evidence. Nutrition 2025;136:112778.

Kankaew S, Briere C-E. Maternal nutrition and human milk nutrients: a scoping review. American Journal of Maternal and Child Health Nursing. 2025;50(1):doi: 10.1097/NMC.0000000000001059.

Moon RJ, D'Angelo S, Curtis EM. Pregnancy vitamin D supplementation and offspring bone mineral density in childhood: follow-up of a randomised controlled trial. The American Journal of Clinical Nutrition. 2024;120(5):DOI:10.1016/j.ajcnut.2024.1009.1014.

National Health and Medical Research Council. (n.d.). Healthy eating when you’re pregnant or breastfeeding. Eat for Health. https://www.eatforhealth.gov.au/eating-well/healthy-eating-throughout-all-life/healthy-eating-when-you’re-pregnant-or-breastfeeding

National Health and Medical Research Council. (2012). Infant Feeding Guidelines. Information for health workers. https://www.nhmrc.gov.au/about-us/publications/infant-feeding-guidelines-information-health-workers#block-views-block-file-attachments-content-block-1

National Health and Medical Research Council. (2010). Public statement: Iodine supplementation for pregnant and breastfeeding women. https://patientinfo.org.au/patientinfo/NHMRC%20Iodine%20Supplementation%20Fact%20Sheet.pdf

Perichart-Perera O. Nutrition for optimal lactation. Annals of Nutrition and Metabolism. 2024:DOI: 10.1159/000541757.

Perrin a, Fogleman A, Newburg D, Allen J. A longitudinal study of human milk composition in the second year postpartum: implications for human milk banking. Maternal and Child Nutrition. 2017;13(1):e12239. doi: 12210.11111/mcn.12239.