Dr Clare Wall and colleagues of the University of Auckland recently reported in an interesting paper the vitamin D levels of exclusively breastfed infants in New Zealand.
They studied 94 infants, mostly of European ancestry, whose average age was 10 weeks. They reported the following:
- The average vitamin D levels of the 94 infants were 21 ng/ml.
- In all, 24% of infants had serum 25(OH)D concentration <11 ng/ml, levels associated with rickets.
- Infants enrolled during winter had a median level of 8 ng/ml while infants tested in the summer had a median concentration of 30 ng/ml. The highest level was 40 ng/ml.
- Because of ozone depletion in the southern hemisphere, New Zealand’s peak summer ultra violet index values are 40% greater than at corresponding northern hemisphere latitudes.
The authors concluded,
“The infants in this study were predominantly European and considered low risk; however, they still demonstrated low 25(OH)D levels particularly during the winter months. The clinical significance of the low levels particularly in the winter months is not yet understood but there is much evidence to support the importance of vitamin D sufficiency for health.
Furthermore, they recommended,
“Sunlight exposure is the most effective way to improve vitamin D status but is not practical or safe for young infants. Also the enormous seasonal variability in ultraviolet B irradiation and the diversity of skin pigmentation in New Zealand’s population make recommendations around sun exposure and vitamin D very difficult to apply to the individual. Vitamin D supplementation of exclusively breastfed infants should be considered as part of New Zealand’s child health policy.”
I agree with this advice, at least for very young infants whose mothers are not sufficient in vitamin D. As we have blogged on before, mothers who supplement with vitamin D at 5000 IU/day or more can give their child enough vitamin D in their breast milk.
For the 99% of mothers who don’t take that much vitamin D, supplementing their babies is most practical. Since babies’ skin may be more delicate than older children, I think it’s best to be fairly sensible in giving your infant sun exposure, limiting it to ten minutes per day of full body sun exposure when your shadow is shorter than you are. While infants should still receive some sun exposure, just remember they may burn faster than adults, especially while they are vitamin D deficient. I believe that historically, infants were hidden away by paleolithic mothers, and got most of their vitamin D from breast milk and not sun exposure.