Preventing vitamin D deficiencies in pregnant women might be important for ensuring normal development in children, say UK researchers.
Expectant mothers with a deficiency in vitamin D may be putting their children at a greater risk of developmental issues, according to new research published in the British Journal of Nutrition.
A study looking at data from more than 7,000 mother-and-child pairs has found that maternal vitamin D deficiency has a negative effect on the social development and motor skills of pre-school children in the first four years of life.
"The importance of vitamin D sufficiency should not be underestimated,” commented study lead author Dr Andrea Darling from the University of Surrey. “It is well-known to be good for our musculoskeletal systems, but our research shows that if levels are low in expectant mothers, it can affect the development of their children in their early years of life.”
According to the study, pregnant women who were deficient in vitamin D (less than 50 nmol per litre in blood) were more likely to have children in the bottom 25% of pre-school development tests for gross and fine motor development at age two and a half years when compared to the children of vitamin D sufficient mothers.
Vitamin D insufficiency in pregnancy was also found to affect a child's social development at age three and a half, said the team.
However, no associations were found between maternal vitamin D status and other outcomes at older ages – including IQ and reading ability at seven to nine years old.
Darling noted that while vitamin D is found in oily fish like salmon, sardines and mackerel, and in small amounts of red meat, eggs, fortified fat spreads and some breakfast cereals.
However, unless a large portion of oily fish is eaten daily it is difficult to get the recommended daily intake of 10 micrograms per day from food alone, she said.
"Many pregnant women, especially those from minority groups with darker skin (e.g. African, African-Caribbean or South Asian), will still need to take a 10 micrograms vitamin D supplement daily, particularly in the autumn and winter when vitamin D cannot be made from the sun,” Darling commented.
The team noted that evidence from animal studies has suggested that the neurocognitive development of foetuses is affected when levels of vitamin D in the mothers are low.
Indeed, researchers believe that interactions between vitamin D and dopamine in the brain of the foetus might play a crucial role in the neurological development of brain areas controlling motor and social development.
“However, whether higher maternal vitamin D status (serum 25-hydroxyvitamin D (25(OH)D)) in pregnancy is associated with a reduced risk of offspring suboptimal neurodevelopmental outcomes is unclear,” noted the authors.
A total of 7,065 mother–child pairs were studied from the Avon Longitudinal Study of Parents and Children cohort. All pairs had data for both serum total 25(OH)D concentration in pregnancy and at least one measure of offspring neurodevelopment, including: Pre-school development at six to 42 months; ‘Strengths and Difficulties Questionnaire’ scores at seven years; intelligence quotient (IQ) at eight years; reading ability at nine years.
Tests included assessments of their coordination, such as kicking a ball, balancing and jumping and their usage of fine muscles, including holding a pencil and building a tower with bricks.
After adjustment for confounders, the team reported that children of vitamin D-deficient mothers (less than 50·0 nmol/l) were more likely to have scores in the lowest group (the bottom 25%) for gross-motor development at 30 months, fine-motor development at 30 months and social development at 42 months, when compared to vitamin D-sufficient mothers.
“Our results suggest that deficient maternal vitamin D status in pregnancy may have adverse effects on some measures of motor and social development in children under four years,” concluded the team.
“Prevention of vitamin D deficiency may be important for preventing suboptimal development in the first four years of life.”
However, Darling noted that it is important to remember that 'more is not necessarily better'.
“It is important not to take too much vitamin D from supplements as it can be toxic in very high doses."