Pooling data from 16 studies revealed that individual intakes of about 440 IU of vitamin D from fortified foods was effective in boosting vitamin D levels by about 20 nmol/L, according to findings published in the Journal of Nutrition.
Such a boost would help people attain healthy levels of vitamin D, indicated to be between 125-200 nmol/L.
“Vitamin D food fortification increases circulating 25(OH)D concentrations in community-dwelling adults,” said the researchers, led by Lucinda Black from the Vitamin D Research Group at University College Cork
“Safe and effective food-based strategies could increase 25(OH)D across the population distribution and prevent vitamin D deficiency with potential benefit for public health.”
However, studies have reported a 'concerning trend' in declining intakes of vitamin D from foods in the US population, with data published in the Journal of the American Dietetic Association indicating a decrease in vitamin D intake from food of 15% from the early 1980s to 2007-2009.
Numerous experts have voiced concerns about low vitamin D levels, particularly among US children. According to findings published in Environmental Health Perspectives (doi:10.1289/ehp.1003195), many children may not get enough sun exposure to meet their minimum daily vitamin D requirements.
Renowned vitamin D researcher, Michael Holick PhD, MD, Professor of Medicine at Boston University Medical Center, told NutraIngredients-USA.com in 2011 that the most realistic approach to boosting the nation’s intake of vitamin D is for food manufacturers to increase the dose of vitamin D per serving.
According to the new meta-analysis, food is indeed an effective vehicle for boosting vitamin D levels, and public health strategies should consider the results of their new meta-analysis.
Black and her co-workers analyzed data from 16 studies and concluded that for every microgram of vitamin D ingested from fortified foods (40 International Units are equal to 1 microgram), blood levels of the vitamin increased by 1.2 nmol/L.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D).
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 and -2 diabetes.
Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.112.158014
“An Updated Systematic Review and Meta-Analysis of the Efficacy of Vitamin D Food Fortification”
Authors: L.J. Black, K.M. Seamans, K.D. Cashman, M. Kiely