“This is important for exclusively breast-fed infants and dark-skinned children, who are at particular risk of nutritional rickets,” says Mayo Clinic family medicine physician Dr. Tom Thacher, who is not part of the study.
The American Academy of Pediatrics recommends widespread vitamin D supplementation of breast-fed infants to prevent rare cases of rickets, a softening and weakening of bones in children.
“Although rickets is rare, it is entirely preventable with adequate vitamin D and calcium intakes,” says Dr. Thacher.
According to Dr. Thacher, there is no important downside to supplementation as long as it is limited to recommended doses of vitamin D. He adds, new information indicates mothers may be able to enrich their breast milk with adequate vitamin D for an infant, if they take high enough doses themselves.
Vitamin D promotes the absorption of calcium and phosphorus from the gastrointestinal tract. A deficiency of vitamin D makes it difficult to maintain proper calcium and phosphorus levels in bones, which can cause rickets. Children 3 to 36 months old are most at risk for rickets because their skeletons are growing so rapidly.
Researchers in the Canadian study found children who were breast-fed up to 36 months and did not take supplements were more likely to develop vitamin D deficiency even though they had started eating solid foods.
“Sometimes vitamin D levels are low or insufficient but not in the extremely low range that can cause rickets,” cautions Mayo Clinic pediatrician Dr. Phil Fischer, who is not part of the research. “This new study shows vitamin D levels are higher in supplemented children after the first year of life, but it is not clear there is any clinical significance to these variations in vitamin D level.”
Dr. Fischer recommends seeking input about vitamin D supplementation from a health care provider, noting too much of the vitamin is also bad. “We occasionally see children who are very sick due to over-supplementation with vitamin D, so parents giving supplements must be very careful to give the appropriate amount.”