Poor vitamin D status is associated with an increasing list of disorders and diseases such as cancer, metabolic syndrome, insulin resistance, type 1 diabetes, type 2 diabetes and multiple sclerosis. The accepted biomarker for vitamin D status is 25-hydroxyvitamin D [25(OH)D], and accumulating evidence suggests that during the winter months much of the population in high latitude countries develop sub-optimal serum levels of 25(OH)D. For children, the optimal levels of serum 25(OH)D is thought to be greater than 50nmols/L, but these levels are difficult to achieve without sunlight exposure or supplements because food sources of vitamin D are limited. As a consequence, the fortification of food with vitamin D is considered a possible solution to this problem by some. Fortification of milk with vitamin D would create a functional food that could enable high year round levels of vitamin D.
Researchers1 have investigated the effects of vitamin D fortified milk on the 25(OH)D serum levels of toddlers aged 12 to 20 months. The study was conducted in Dunedin, New Zealand, where year round vitamin D production is not possible. The fortified milk provided a mean vitamin D intake of 3.7µg/d and was administered to toddlers over a 20 week period. Vitamin D levels were significantly higher in the milk group, compared to the placebo group at 20 weeks. The prevalence of having 25(OH)D below 50nmol/L decreased from 43% to between 11 and 15% in the milk fortified group. This would tend to suggest that fortified milk is a useful functional food for increasing the vitamin D status of children and could be an effective way to optimise year round vitamin D levels. The fortified milk was most effective during the winter months, as would be expected.
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