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Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data

BMJ 2017; 356 doi: https://doi.org/10.1136/bmj.i6583 (Published 15 February 2017) Cite this as: BMJ 2017;356:i6583

Re: Vitamin D supplementation to prevent acute respiratory tract infections.

Martineau et al. have demonstrated a clear association between incidence of acute respiratory illness and vitamin D deficiency in the 1.1-15.9 years age group (1). However, their subsequent assertion that “Vitamin D supplementation was safe” and that “These findings support the introduction of public health measures such as food fortification to improve vitamin D status” are potentially open to misinterpretation by the general public and need to be viewed with caution.

UK media coverage of this scientific study was accompanied by extrapolative quotes that “daily or weekly vitamin D supplements will mean 3.25 million fewer people would get at least one acute respiratory infection a year” (2,3). The study’s recommendations were widely re-interpreted in the national press with headlines including “Vitamin D supplements 'the key to beating colds and flu'” (Independent) and “Vitamin D 'proved to cut risk of colds and flu'“ (The Guardian).

Well intentioned but inadvertent hypervitaminosis D is not a new phenomenon. It has occurred previously in both agricultural and human nutritional interventions. In captive animals, providing vitamin supplementation is often essential in order to mimic the wild environment (4,5,6). The use of UVB light as a source of vitamin D is ideal in that it does not carry any risk of toxicity, however, over supplementation with dietary vitamin D does, and vitamin D toxicosis has been observed in mammalian breeding groups (5,7,8,9,10). Pet food has also had to be recalled due to extreme levels of certain nutrients including, but not limited to, vitamin D3 (11). The problems of dietary supplementation invariably occur when supplements are either provided in addition to a diet that is already sufficient or when the supplementary dose is too high, as is often the case in large groups, in which requirements may not be homogenous. Notably, during the 1940s and 1950s there was widespread fortification of human foodstuffs aimed at preventing rickets. However, in 1957 the Ministry of Health Joint Subcommittee on Welfare Foods needed to take action to halve infantile intake of vitamin D to tackle the increase in incidence of infantile hypercalcaemia (12,13).

In 2012-13 the UK Teratology Information Service reported concerns relating to vitamin D were in the top 15 most frequent telephone enquiries that year, reflecting an increased consumption of dietary supplements (14). An online search for “vitamin D supplement” reveals a range of easily available non-prescription preparations containing daily doses of 400 – 10,000 IU. Adoption of some of these daily supplements would supply well above the current Scientific Advisory Committee on Nutrition (SACN) recommended reference nutrient intake (RNI) from all dietary sources of 10 mcg (400 IU) vitamin D per day for the general population aged 4 years and older (15).

Whilst controlled and targeted dietary fortification may indeed be of benefit, it is important that scientific advice be carefully worded so as not to be taken out of context where it might be misconstrued to be of generalized benefit for all and indeed cause as much harm as good.

References

(1) Martineau AR et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017;356:i6583. doi: https://doi.org/10.1136/bmj.i6583
(2) Pickover E. Independent – 2017 February 16th. http://www.independent.co.uk/life-style/health-and-families/health-news/...
(3) Boseley S. Health Editor: The Guardian – 2017 February 15th. https://www.theguardian.com/science/2017/feb/15/adding-vitamin-d-to-food...
(4) Lopez I, Pineda C, Muñoz L, et al. Chronic vitamin D intoxication in captive Iberian lynx (Lynx pardinus). PLoS One 2016;11:1–10. doi:10.1371/journal.pone.0156331
(5) Wallach JD. Hypervitaminosis D Green Iguanas. Veterinary Medical Association 1966;149:912–4
(6) Ferguson GW, Brinker AM, Gehrmann WH, et al. Voluntary exposure of some Western-Hemisphere snake and lizard species to ultraviolet-B radiation in the field: How much ultraviolet-B should a lizard or snake receive in captivity? Zoo Biol 2010;29:317–34. doi:10.1002/zoo.20255
(7) Ferguson GW, Jones JR, Gehrmann WH, et al. Indoor husbandry of the panther chameleon Chamaeleo Furcifer pardalis: Effects of dietary vitamins A and D and ultraviolet irradiation on pathology and life‐history traits. Zoo Biology 1996;15:279–99. doi:10.1002/(SICI)1098-2361(1996)15:3<279::AID-ZOO7>3.3.CO;2-T
(8) Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. The American Journal of Clinical Nutrition 2004;79:362–71. doi:14985208
(9) Webb AR, Decosta BR, Holick MF. Sunlight regulates the cutaneous production of vitamin D3 by causing its photodegradation. Journal of Clinical Endocrinology and Metabolism 1989;68:882–7. doi:10.1210/jcem-68-5-88
(10) Martínez F, Manteca X, Pastor J. Retrospective study of morbidity and mortality of captive Iberian Lynx (Lynx pardinus) in the ex situ conservation programme (2004-June 2010). Journal of Zoo and Wildlife Medicine 2013;44:845–52. doi:10.1638/2011-0165R4.1
(11) Rumbeiha W, Morrison J. A Review of Class I and Class II Pet Food Recalls Involving Chemical Contaminants from 1996 to 2008. Journal of Medical Toxicology 2011;7:60–6. doi:10.1007/s13181-010-0123-5
(12) Bransby ER, Berry WTC, Taylor DM. Study of the Vitamin-D Intakes of Infants in 1960. BMJ 1964;1:1661–3. doi:10.1136/bmj.1.5399.1661
(13) British Paediatric Association. Infantile Hypercalcaemia, Nutritional Rickets, and Infantile Scurvy in Great Britain. A British Paediatric Association Report. BMJ 1964;1:1659. doi: https://doi.org/10.1136/bmj.1.5399.1659
(14) National Poisons Information Service Report 2012/13. Public Health England. http://www.npis.org/NPISAnnualReport2012-13.pdf
(15) SACN vitamin D and health report. Public Health England (21st July 2016) https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report

Competing interests: No competing interests

28 February 2017
Katherine S McIndoe
Animal Conservation Masters student
McIndoe AK
University of Bristol
31 Shirehampton Road, Bristol