12 January - 20 June 2016

Setting vitamin D dosage levels

8 May 13

A study published in the Journal of the American Medical Association investigates the effect of different dosages of oral vitamin D supplementation on vitamin D status in healthy, breastfed infants.  The recommended daily intake of vitamin D in infants varies across the globe.  In the US and Canada 400IU per day is recommend to maintain a plasma concentration of 75 to 150 nmol/L 25-hydroxyvitamin D (25[OH]D).   Contrastingly France and Finland recommend over 1000nmol.  Researchers at McGill University sought to define recommendations; the objective being to 'establish a dose of oral vitamin D that would support 25(OH)D concentrations of 75 nmol/L or greater in 97.5% of breastfed infants by 3 months of age.'  As a secondary objective the trial intended to measure bone mineral accrual as well as growth. The trial was randomised and double-blind.  132 babies were each given a dose of either 400IU/day; 800IU/day; 1200IU/day or 1600IU/day.  The plasma tested in those taking 1600IU/day was shown to reach concentrations that 'have been associated with hypocalcaemia' and so was discontinued.  Until the point of discontinuation however this was the only group that met the levels the researchers set out to achieve.  After 3 months only 55% of the 400IU/day group had reached the desired concentration; 81% in the 800IU/day group and 92% in the 1200IU/day group.  97.5% of all infants failed to maintain this plasma 25(OH)D concentration after 12 months.  It is relevant to mention however that 50nmol/L concentration were maintained in 98% of all infants.  The study was also able to conclude that differing dosage did not affect growth or bone mineral content.  Further studies are required before sound recommendations for vitamin D supplementation in infants can be made.  

Another recent study by researchers from John Hopkins has indicated that plasma vitamin D levels, higher than the top of the range reported by the Institute of Medicine provide no additional benefit.   Previous unpublished studies by the team, suggested  the potential harm from higher vitamin D levels in healthy people.  They found that beyond blood levels of 21 nanograms per millilitre, any additional increase in vitamin D was associated with an increase in c-reactive protein, a factor linked to stiffening of the blood vessels and an increased risk of cardiovascular problems.  Amer et al report that some groups, for example the elderly, postmenopausal women however may benefit from higher blood levels of a vitamin vital to bone health. The current study published in The American Journal of Medicine analysed data from more than 10,000 participants in the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2004 and matched this to mortality data from the National Death Index through Dec. 2006.  After looking at deaths from all causes and specifically cardiovascular disease, Amer et al. found that those with blood levels of 21 nanograms per millilitre of 25-Hydroxyvitamin D -- at the top of the range that the IOM considers "adequate" and at the low end of "normal" -- cut their risk of death in half. Above 21 nanograms per millilitre, the data suggest that the protective effect appears to wear off.

RSSL's Functional Ingredients Laboratory provides vitamin analysis in a wide range of matrices including drinks, fortified foods, pre-mixes and multi-vitamin tablets, including the analysis for  Vitamin D2 and Vitamin D3.  It provides a full vitamin and mineral analysis service to assist with labelling, due diligence, claim substantiation and stability. For more information please contact Customer Services on Freephone 0800 243482 or email enquiries@rssl.com

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