Vitamin D and Nursing

Why is Vitamin D important for nursing?
​Your demand for Vitamin D does not end at delivery; in fact, requirements are even higher during breastfeeding than they are during pregnancy. Maintaining adequate levels is crucial for several reasons:

• Impact on Baby’s Health: A mother’s Vitamin D levels directly affect the baby's levels because the nutrient is passed via the placenta during pregnancy and through breast milk after birth.
• Preventing Deficiency: Chronic deficiency in infants can lead to rickets, a softening of bone tissue that causes skeletal deformities like bowlegs, and can even cause dental enamel defects that lead to cavities later in childhood.
• Long-Term Protection: Adequate Vitamin D intake early in life is linked to a lower risk of autoimmune diseases, such as Type 1 diabetes, and may even protect against high blood pressure and arterial stiffness in children.

Why is breastmilk frequently low in Vitamin D?
Vitamin D deficiency is a global epidemic, affecting up to 95% of pregnant and lactating women in some regions. Because most mothers have insufficient levels, their breast milk does not naturally contain enough Vitamin D to meet an infant's needs.

The key to Vitamin D transfer is the specific form that moves into breast milk. Research indicates that  Vitamin D3 (cholecalciferol)—the "parent" form found in supplements and produced by the sun—is the form that transfers through breast milk, rather than the major circulating storage form (25-hydroxyvitamin D). Because Vitamin D3 has a short half-life in the blood, consistent daily intake via sun or supplements is more important for a nursing baby than the mother's overall blood storage levels.

How much Vitamin D does Mom and baby need?
There is a significant gap between official guidelines and current research for lactating women:

• Official Recommendations: The standard RDA is 600 IU per day for lactating women. Additionally, the American Academy of Pediatrics recommends that breastfed infants receive 400 IU of oral Vitamin D drops daily.
• Latest research: Research has shown that high-dose maternal supplementation can be an effective alternative to giving the baby drops. Studies show that a maternal dose of 4,000 to 6,400 IU of Vitamin D3 daily is safe and provides enough Vitamin D for Mom and enough in breast milk for baby.
• Higher dose safety: Randomized controlled trials using 4,000 IU daily have observed no adverse events or safety concerns, such as high blood calcium associated with the formation of kidney stones.

Ways to get enough Vitamin D

• Sun Exposure: The primary natural source is sunlight, but this is limited by latitude, living north of the 37th parallel (which Kansas is) does not have enough exposure in the winter and spring for your skin to produce adequate Vitamin D. Melanin (darker skin requires up to 6x more sun exposure), and sunscreen use (SPF 30 blocks 95-98% of production) also block or reduce production of Vitamin D through the skin.
• Supplement with D3: Choose Vitamin D3 over D2, as it is more effective at sustaining blood levels.
• Nutrient Synergy: Vitamin D works best when taken with fatty foods and synergistic nutrients like Magnesium, Vitamin K2, and Vitamin A.​

Think of Vitamin D as the "master contractor" of a construction site. While you provide the bricks (calcium) and wood (phosphorus) to build your baby’s growing body, the master contractor is required to tell the workers where to put those materials to ensure the structure is sound. Without enough contractor presence (daily D3), the "supplies" in your milk cannot be used effectively by your baby.

Sources:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7905986/
https://www.medicalnewstoday.com/articles/161618
https://nutritionsource.hsph.harvard.edu/vitamin-d/
​https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-deficiency/faq-20058397
https://lilynicholsrdn.com/vitamin-d-pregnancy/