The study shows that a healthy intake of vitamin D - the ‘sunshine vitamin’ - in the first year of life appears to set children up to have more muscle mass and less body fat as toddlers.
The findings, published in the journal Pediatric Obesity, emerged from research initially aimed at confirming the importance of vitamin D for bone density.
The additional benefit in terms of body composition came as a surprise for the researchers.
Doctor Hope Weiler, one of the study’s authors and director of the Mary Emily Clinical Nutrition Research Unit at McGill University in Canada, said: “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.”
For the first time, a connection was made between the benefits of achieving healthy vitamin D status during a baby’s first 12 to 36 months and how muscle mass develops.
The researchers achieved this by following up on a 2013 study in which 132 infants in Montreal were given a vitamin D3 supplement at one of four different dosages between the ages of one month and 12 months.
The new study confirmed the importance for the development of strong bones of a vitamin D supplement of 400 IU/day during a baby’s first year. The amount is in line with current Canadian health guidelines.
The researchers found that higher doses did not provide any additional benefit - at least not in terms of bone development.
But the body scans used to assess bone density also allowed the team to measure the children’s muscle and fat mass.
While there were no significant differences in body composition across the different dosage groups, the researchers found children who had vitamin D stores above the threshold recommended by the Canadian Paediatric Society averaged around 450 grams less body fat at three years of age.
Further analysis also indicated a correlation between lean muscle mass and the average level of vitamin D in the body over the first three years of a child’s life.
Dr Weiler said the only other factor found to make a significant difference to the children’s amount of body fat was their level of physical activity.
Vitamin D is also found in a small number of foods. Good food sources include oily fish - such as salmon, sardines and mackerel - eggs, fortified fat spreads, fortified breakfast cereals and some powdered milks.