Many factors contribute to adolescent and adult vitamin D deficiency. However, there is one major variable that affects the vitamin D status of infants, and that is breastfeeding. Because breast milk is the only source of vitamin D for newborns until food or formula are introduced, infants are entirely reliant on their mother’s vitamin D levels to supply their own.
With such high rates of deficiency in adults, researchers evaluated the prevalence of vitamin D deficiency in young Japanese children under the age of four years. A total of 290 children were divided into three groups based on their age. The youngest group included infants aged 0-5 months, the middle group included infants 6-15 months and the oldest group included those between 16-48 months. All of the children were born within normal gestation, were not diagnosed with any disease and were not supplemented with vitamin D.
The researchers measured vitamin D status in all the children. Levels below 12 ng/ml (30 nmol/l) were considered deficient, while insufficient was defined as levels between 12–20 ng/ml (30–50 nmol/l) and sufficient status was defined as levels above 20 ng/ml (50 nmol/l).
This is what the researchers found:
- Of all the children, 7.2% were deficient, 13.8% were insufficient and 79% were sufficient.
- In those in the middle and older age groups, where food had been introduced, rates of deficiency and insufficiency were only 1.7% and 12.9%, respectively.
- In comparison, in the youngest age group, deficiency and insufficiency rates were 34% and 18%, respectively.
- In the youngest age group, median vitamin D levels were much lower in breastfed infants compared to formula-fed infants (p < 0.01).
- Vitamin D deficiency rates were higher in the breastfed group at 50% compared to the formula-fed group at 10.5%.
The researchers concluded:
“In the present study, half of the breast-fed infants were classified as being in the vitamin D deficient state, and 14.6% of the infants and young children aged 6–48 mo to whom food had been introduced were classified as being in the vitamin D deficient and insufficient state.”
To avoid deficiency in their offspring, it is very important for pregnant and breastfeeding women to supplement with vitamin D. The Vitamin D Council recommends supplementing with 5,000 – 10,000 IU (125 – 250 mcg) per day to ensure all mothers and their babies achieve optimal levels (40-80 ng/ml; 100-200 nmol/l).