Infants who consume a healthy amount of vitamin D in the first 12 months of their lives seem to have more muscle mass and less body fat by the time they are 3 years old, says research published in the journal Pediatric Obesity.
[toddler walking in sun]
Vitamin D from sunlight and supplements contributes to healthy development of bones and muscles.

Previous studies have indicated that vitamin D is important for bone density, but the authors of the current study were surprised to find that it also appears to benefit early body composition.

The Centers for Disease Control and Prevention (CDC) say that, while breast-feeding is an important source of necessary nutrients and immune factors, and is considered the best way to feed infants, the vitamin D in breast milk is not sufficient to meet all the child’s needs.

Exposure to sunlight enables the skin to synthesize vitamin D.

However, the vitamin may be lacking among those who live in regions with short daylight hours in winter, where there is limited sunlight or where clouds or pollution prevent sun exposure. People with darker skin types are also susceptible to low vitamin D levels.

There is also a call to keep children from sunlight because of the risk of sun burn and skin cancer. The CDC urge parents to seek shade, cover their children up with suitable clothing, and to use sun block.

Elsewhere, Health Canada have called on parents and caregivers to avoid the use of sun block in young infants.

Concerns have been voiced in the United States about the prevalence of rickets, a condition associated with insufficient vitamin D in which bones do not develop properly.

Experts recommend Vitamin D supplementation for infants until they are old enough for their diet to provide it.

Vitamin D, bone density, and muscle mass

Researchers from McGill University in Montréal, Canada, followed up on a 2013 study involving 132 infants to see if there was any link between healthy vitamin D status in the first 12-36 months and bone density.

Fast facts about mental health

  • Vitamin D occurs naturally in fish oil, liver and egg yolk
  • UVB radiation enables vitamin D to be produced in the skin
  • Vitamin D cannot be stored in the body: its half-life in the body is 1-2 days.

Learn more about vitamin D

The subjects had received a supplement of vitamin D-3 at one of four different dosages between the ages of 1-12 months. The doses were 400, 800, 1200, or 1600 IU a day.

The participants underwent body scans that enabled the team to assess bone density, but the scans also provided information about the development of muscle and fat mass.

Data from the scans showed that higher doses of Vitamin D-3 did not provide any extra advantage for bone development, but they also revealed surprising findings about muscle and fat mass.

The children whose Vitamin D stores were above the 400 IU threshold recommended by the Canadian Pediatric Society (CPS) averaged around 450 grams less body fat at the age of 3 years, compared with those with low vitamin D levels.

Across the different dosage groups, differences in body composition were not significant.

The authors also found an association between lean muscle mass and average vitamin D levels in the body over the first 3 years of a child’s life.

Apart from the level of physical activity, this is the only factor that has been found to make a significant difference to a child’s body fat.

Limitations include the homogeneity of the group in terms of health status, size, high prevalence of breast-feeding, similarity in macronutrient and micronutrient intake, and ethnicity – the sample being mostly white.

Nevertheless, the team believes that the findings are interesting.

“We were very intrigued by the higher lean mass, the possibility that vitamin D can help infants to not only grow healthy skeletons but also healthy amounts of muscle and less fat.”

Hope Weiler, director of the Mary Emily Clinical Nutrition Research Unit at McGill

The study confirms the importance of children receiving vitamin D supplement of 400 IU a day in the form of drops during the first 12 months of life, as recommended by current Canadian health guidelines.

Find out more about a new sunscreen that could offer solar protection without losing exposure to vitamin D.