To the Editor: The Working Group of the Australian and New Zealand Bone and Mineral Society, Endocrine Society of Australia and Osteoporosis Australia are to be commended for their clear and succinct position statement on vitamin D and bone health.1 This statement highlights an important public health issue which is under-recognised in this country. Of particular value is the box of recommendations on high-risk groups, testing and treatment.

However, I believe an important high-risk group has been omitted, a group which too often escapes the notice of the broader medical community. People with intellectual disability have been shown to be at particularly high risk of low vitamin D levels, reduced bone density and fractures.2-5 The reasons for this are multifactorial and include poor mobility, insufficient sun exposure, reduced muscle mass and strength, problems with dietary intake, and medications which interfere with vitamin D metabolism.3,4 There is also some evidence that people with intellectual disability are prone to premature ageing, together with the health problems associated with older age in the general population.3 Some conditions which cause or are associated with intellectual disability are also linked with hypogonadism and reduced peak bone mass.4

To add to all of this, several of the above risk factors, vitamin D deficiency itself, and the increased incidence of epilepsy in the population with intellectual disability, also result in an increased incidence of falls and trauma.5 This unfortunate combination of poor bone health and increased risk of falls and trauma results in a markedly increased incidence of fracture when compared with age- and sex-matched controls from the general population.2-5

In conclusion, people with intellectual disability, particularly those with poor mobility or who are also being treated for epilepsy, should be added to the list of high risk groups. It is likely that the relatively simple steps set out in the position statement (screening for vitamin D deficiency and supplementation) will result in substantial health benefits for this small but particularly vulnerable group of people.

To the Editor: We read with alarm the extraordinary statements in the position statement on vitamin D and adult bone health published recently in the Journal.1 The suggestion that “it is a fallacy that Australians receive adequate vitamin D from casual exposure to sunlight” is not true.

The suggested basis for this statement is an extraordinary extrapolation from a single study in which a small number of volunteers had whole body exposure on one occasion for 10–15 minutes to midday summer sun in Boston. It is not possible to extrapolate in such a way from this single demonstration, as the effect of shorter exposure times or repeated daily exposures were not examined. In fact, a study in Australia showed that the adult population (including those aged over 70 years) received sufficient sunlight while using sunscreen to ensure that no-one was found to have vitamin D deficiency during the study period.2

While it is well accepted that ultraviolet B (UVB) radiation is essential for the formation of vitamin D3 in the skin, it is equally well established that continued exposure of vitamin D to UVB radiation results in its degradation. Hence, the importance of knowing the effect of lower sun exposures on vitamin D production.

It is intriguing that the authors of the position statement recommended a daily sun exposure dose that they calculate will produce 1000 IU of vitamin D, but, if sun exposure is not possible, a vitamin D supplement of at least 400 IU per day.

The high prevalence of vitamin D deficiency among institutionalised older Australians is a tragedy, but this cannot be used as the basis of advice for the general population who do receive daily sun exposure and appear to be the target of the statement. Nor can the mild vitamin D deficiency found in a single study in southern Victoria be used to recommend sun exposure in more northern Australian climes. Finally, while vitamin D supplementation has been shown to reduce the risk of fractures in the elderly, the proposed beneficial effect of deliberate sun exposure has not been demonstrated.

Recently, a joint position statement was approved by the Australian and New Zealand Bone and Mineral Society, Osteoporosis Australia, the Australasian College of Dermatologists and the Cancer Council Australia. This included the statement that “The majority of Australians generally have sufficient ultraviolet radiation exposure to enable adequate vitamin D production . . . to form and maintain healthy, strong bones”.3 This statement, endorsed only a few weeks ago, is in obvious conflict with the position statement from the same organisations that was published in this Journal. The latter puts the vast majority of Australians at further risk of skin cancers, which are already epidemic in our country.4

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.