Vitamin D insufficiency is increasingly being recognised as a common health concern amongst high latitude Western populations. Vitamin D is produced in the skin via the action of ultraviolet light on cholesterol, but the absence or avoidance of sun exposure causes a decrease in this production. Plasma levels of 25-hydroxyvitamin D [25(OH)D] are the accepted biomarker for vitamin D status, and during the winter months plasma concentrations can fall to levels below those recommended for optimal health (25-hydroxyvitamin D plasma levels over 40 ng/mL or 100 nmol/L). In some vulnerable populations such as the elderly and infirm, the absence of year round sun exposure can decrease plasma levels of 25-hydroxyvitamin D below the threshold for classification of vitamin D deficiency. Therefore many researchers now claim that supplements of vitamin D are required to maintain optimal year round vitamin D concentrations. One way of achieving this might be the fortification of foods with vitamin D.
That vitamin D fortification of foods is effective at raising plasma concentrations of 25-hydroxyvitamin D has been demonstrated in research recently published in the Journal of Nutrition1. In a meta-analysis of previously published studies, the researchers analysed data to investigate the rise in plasma levels of 25-hydroxyvitamin D with vitamin D fortified foods. The authors included 16 studies that met their criteria, 14 of which showed a significant effect of fortified foods on plasma levels of 25-hydroxyvitamin D. The authors found large heterogeneity (variation) between studies in terms of the effects of the fortified foods, and determined that this was due to the latitude of the study, baseline concentrations of 25-hydroxyvitamin D and dose of vitamin D ingested. A mean intake of ~11 µg per day vitamin D (440 IU per day) from fortified foods increased 25-hydroxyvitamin D concentrations by 19.4 nmol/L. This equated to a 1.2 nmol/L increase in 25-hydroxyvitamin D for every 1 µg vitamin D ingested.
Therefore fortifying foods with vitamin D is effective at raising plasma concentrations of 25-hydroxyvitamin D. This might be a possible solution for raising plasma levels of those at risk of vitamin D insufficiencies and more vulnerable groups at risk of deficiencies. However, fortification of foods with vitamins amounts to forced medication because no consent is given. Further, those already taking supplements may experience toxicity by the addition of vitamin D from fortified foods to their diet. It may be fair to conclude that we can fortify foods with vitamin D, but we should really be asking if we should be fortifying foods with vitamin D. Supplements are readily available and have been shown to raise plasma levels of 25-hydroxyvitamin D effectively and safely, and using supplements gives the individual the ability to consent to any treatment. The need for fortification of foods with vitamin D (or any vitamin) may therefore not only unethical, but also unnecessary.
RdB
