Vitamin D and adult bone health in Australia and New Zealand: a position statement

In reply: We agree with Vanlint that any individual who has limited mobility, or is housebound or institutionalised, is at risk of vitamin D deficiency, as highlighted in Box 3 of the position statement.1 Disability in general is likely to be a risk, with motor disability as well as intellectual disability liable to limit sun exposure. The problem may be further exaggerated by any increased risk of falls or convulsions.

Chia and colleagues have raised important issues. After a number of meetings, the Cancer Council of Australia, the Australasian College of Dermatologists and the Australian and New Zealand Bone and Mineral Society developed a considered consensus statement on vitamin D deficiency, risk of skin cancers and sunlight exposure, which was published at <http://www.cancer.org.au/documents/Risks_Benefits_Sun_Exposure_MAR05.pdf>. This document refers to the position statement published in this Journal in relation to sun-exposure guidelines for vitamin D.

Chia and colleagues’ objection to the abstract of this position statement appears ill-founded. If “a significant number of Australians are deficient in vitamin D”, then it follows logically that “it is a fallacy that Australians receive adequate vitamin D from casual exposure to sunlight”, as sunlight is the main source of vitamin D in Australia. The significant number of Australians deficient in vitamin D are not the majority, as was clearly shown in the article, so this statement does not conflict with the complementary statement in the risks and benefits statement.

We stand by our original claim that a number of groups in the Australian community have a high prevalence of vitamin D deficiency, including elderly men with hip fracture (63%), Muslim women (68%), elderly ambulant men with prostate cancer (34%), “healthy” elderly men living in Southern Sydney (16%), healthy community-dwelling, ambulatory women in Geelong (20% in the age group 20–39 years, increasing to 53% in older age groups), men and women (some with psychiatric disorders) in south-east Queensland (23%), and even pregnant women in south-eastern Australia (7%) (references are available from the authors on request).

As noted in the position statement, and by Chia and colleagues, continued exposure to ultraviolet (UV) radiation may lead to degradation of pre-vitamin D, so that short exposures are likely to be more efficient. This degradation is marked only at relatively high UV doses.2 Studies that used lower UV doses2,3 produced indirect UV equivalence data similar to those quoted in the position statement.1 As the relationship between UV exposure and vitamin D dosage varies from person to person, and as sun exposure is also likely to be variable and on most days, rather than every day, the recommendation that vitamin D supplementation be at least 400 IU/day in people likely to be at risk of inadequate skin-derived vitamin D is entirely appropriate.

We strongly agree with Chia and colleagues about the need to avoid sun damage while still obtaining the small amount of sun exposure needed to make adequate vitamin D, which is why the position statement advocates short exposures, easily achieved by casual exposure, and reiterates other Sun-Safe messages, such as avoidance of exposure in peak UV periods and the use of sunscreens where appropriate.