Vitamin D is important for the growth of healthy bones and to prevent rickets, and it is particularly crucial that infants get enough of it during their first year life because their bones are growing very quickly.
For that reason, pediatricians often suggest that parents give babies a daily vitamin D supplement. A previous study showed that although breastfeeding is the ideal way to feed infants, supplementation with vitamin D, starting soon after birth, is advised because breastfed babies typically do not receive sufficient vitamin D from other sources.
However, current recommendations about how much vitamin D babies should receive vary widely, according to the scientists.
In the current study, led by Prof. Hope Weiler, from the School of Dietetics and Human Nutrition at McGill University, and Dr. Celia Rodd of McGill's Department of Pediatrics, experts found that 400 IU of vitamin D each day is adequate for infant health.
Prof. Weiler said:
"There's sometimes a feeling that more is better. But until now, no one had compared the popularly recommended daily doses of vitamin D to see what will result in optimal health for infants, so we were very glad to be able to do this."
The recommended daily dose of vitamin D in France and Finland is of 1,000 IU for infants, while a daily dose of 400 IU is suggested by Health Canada and the World Health Organization (WHO).
The Canadian Pediatric Society differentiates between winter and summer months and advises that babies should receive 800 IU each day during the winter when they are less exposed to the sun.
The researchers in the new study followed a group of 132 babies in Montreal who were randomly assigned to be given different daily doses of vitamin D over a 12-month period. The doses included 400 IU per day, 800 IU, 1200 IU and 1600 IU.
The infants' weight, length, and head circumference were measured after their initial intake in the investigation. The scientists also looked at the levels of vitamin D in their blood at three months, six months, nine months, and one year of age.
The team also examined how much mineral was added to the children's bones as they got bigger.
The authors said:
"It was clear, as early as the three-month mark, that there was no advantage to the higher doses of vitamin D and that 400 IU per day was sufficient."
"The parents that we saw in the study were highly motivated and made sure that their babies were taking the vitamin D on a daily basis," Dr. Rodd pointed out.
Higher doses of the vitamin did not offer any extra benefits in terms of helping the infants grow a healthy skeleton.
In 2010, the FDA (Food and Drug Administration) suggested that infants receive no more than 400 IU of vitamin D each day.
According to that report, excessive amounts of the vitamin can be harmful to infants and may cause nausea and vomiting, loss of appetite, excessive thirst, frequent urination, abdominal pain, constipation, muscle and joint aches, muscle weakness, fatigue, confusion, and kidney damage.
The group of babies observed had relatively good amounts of vitamin D at the start of the research, the authors said.
Therefore, more research is needed to clarify whether higher amounts of the vitamin are necessary for infants with lower vitamin D at birth.
Written by Sarah Glynn