Vitamin D level reassessment high priority, say experts
dietary recommendations for vitamin D, experts have said, because
current advice is outdated and puts the public at risk of
deficiency.
Fifteen experts from universities, research institutes, and university hospitals around the world, led by Reinhold Vieth from Toronto's Mount Sinai Hospital wrote in the American Journal of Clinical Nutrition: "We call for international agencies such as the Food and Nutrition Board and the European Commission's Health and Consumer Protection Directorate-General to reassess as a matter of high priority their dietary recommendations for vitamin D, because the formal nationwide advice from health agencies needs to be changed." "The balance of the evidence leads to the conclusion that the public health is best served by a recommendation of higher daily intakes of vitamin D. Relatively simple and low-cost changes, such as increased food fortification or increasing the amount of vitamin D in vitamin supplement products, may very well bring about rapid and important reductions in the morbidity associated with low vitamin D status," they said. The editorial was written in response to a UK-based study, published in the same journal, which reported that there exists an alarmingly high prevalence of hypovitaminosis D in the general population during the winter and spring. Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet. Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body. The study, by Elina Hyppönen and Chris Power from the Institute of Child Health in London, measured the level of 25(OH)D in 7437 whites from the 1958 British birth cohort when the subjects had reached the age of 45. Hyppönen and Power report that prevalence of low vitamin D levels was highest during the winter and spring, when 46.6 per cent of participants had 25(OH)D concentrations of less than 40 nanomoles per litre while this fell to 15.4 per cent during the summer and autumn. Vitamin D is produced in the skin on exposure to UVB radiation and can also be consumed in small amounts from the diet. However, recent studies have shown that sunshine levels in some northern countries are so weak during the winter months that the body makes no vitamin D at all, leading some to estimate that over half of the population in such countries have insufficient or deficient levels of the vitamin. "Prevalence of hypovitaminosis D in the general population was alarmingly high during the winter and spring, which warrants action at a population level rather than at a risk group level," concluded the researchers. Vieth and his collaborators said the study was yet another publication in a series that document low vitamin D levels, and this will continue while recommended levels of vitamin D intake remain outdated. "Because of the convincing evidence for benefit and the strong evidence of safety, we urge those who have the ability to support public health-the media, vitamin manufacturers, and policy makers-to undertake new initiatives that will have a realistic chance of making a difference in terms of vitamin D nutrition," wrote Vieth and collaborators. A recent review of the science reported that the tolerable upper intake level for oral vitamin D3 should be increased five-fold, from the current tolerable upper intake level (UL) in Europe and the US of 2000 International Units (IU), equivalent to 50 micrograms per day, to 10,000 IU (250 micrograms per day). Source: The American Journal of Clinical Nutrition March 2007, Volume 85, Number 3, Pages 860-868 "Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors" Authors: E. Hyppönen and C. Power Editorial: The American Journal of Clinical Nutrition March 2007, Volume 85, Number 3, Pages 649-650 "The urgent need to recommend an intake of vitamin D that is effective" Authors: R. Vieth, H. Bischoff-Ferrari, B.J. Boucher, B. Dawson-Hughes, C.F. Garland, R.P. Heaney, M.F. Holick, B.W. Hollis, C. Lamberg-Allardt, J.J. McGrath, A.W. Norman, R. Scragg, S.J. Whiting, W.C. Willett, and A. Zittermann
