Vitamin D: supplement use in specific population groups

The PHAC considered only the implementation of existing recommendations on vitamin D to prevent deficiency. The evidence base on which existing recommendations were made – and the contribution of dietary intake (including fortified foods) and sunlight exposure to vitamin D status – was outside its remit. Whether older adults should take vitamin D alone, or with calcium, was also outside its remit. Members were aware that the Scientific Advisory Committee on Nutrition (SACN) was considering many of these issues. Wherever possible, the guidance is consistent with SACN's advice and ongoing work in this area. NICE is also developing an associated guideline on the benefits and risks of sunlight exposure. It is hoped that these 3 pieces of work will provide the basis for clear, consistent advice to reduce the risk of low vitamin D status among all specific population groups.

A number of fundamental issues hinder the uptake of existing guidance among specific population groups. For example, many health professionals and the public may be unaware that the skin cannot synthesise vitamin D from sunlight during winter months in the UK. They may also be unaware that a balanced diet alone will not provide sufficient vitamin D. In addition, they do not know enough about the importance of vitamin D supplements for specific population groups. The availability of suitable low cost supplements may also be limited – and health professionals and the public may not know where they can get them locally. The PHAC decided that there will only be significant increases in uptake if all these issues are addressed. Members also discussed and made recommendations on other actions to prevent any further confusion about the existing guidance. This includes having a viable distribution policy to reach specific population groups before carrying out further awareness-raising activities.

Advice on the use of vitamin D supplements to maintain good bone health has been available since 1991. (Dietary reference values for food energy and nutrients for the United Kingdom. Report of the panel on dietary reference values of the Committee on Medical Aspects of Food Policy Department of Health.) This includes existing recommendations on vitamin D from SACN, the 4 UK chief medical officers and NICE. However, awareness and implementation of the advice has been poor. The PHAC noted that, although existing recommendations are broadly consistent, the complexity of the advice and poor communications may have been the cause of confusion among both health professionals and the public. Members also noted the lack of clarity about who is 'at risk'. For example, health professionals and the public alike may question what constitutes 'a low exposure' to sunlight or 'dark' skin. Similarly, the disparity between those who are eligible for the Healthy Start scheme and the recommendations on vitamin D supplements for women and children appear to be another source of confusion.

The PHAC discussed the importance of increasing the availability of vitamin D supplements for all specific population groups. Members were unable to recommend free supplements for these groups, due to a lack of evidence on the effect that differential costs have on uptake. They did recognise that free provision had contributed to increased uptake in some areas. Members also noted the strong economic case for offering free or low cost supplements to specific population groups to prevent deficiency, when compared to the cost of widespread testing for vitamin D deficiency. They felt it was important to determine the effectiveness and cost effectiveness of providing free supplements to specific population groups and made a recommendation for research on this. Allied to this, the PHAC discussed the potential for confusion among the public if free or low cost supplements were available in some areas but not others. Members agreed that this issue cannot be ignored by areas considering such a policy.

Until recently, low cost vitamin D-only supplements containing 100% of the reference nutrient intake were not widely available for sale. The PHAC noted that many vitamin D supplements also contain calcium (which may be poorly tolerated) and that some people may be deterred by the cost of supplements. Members agreed that there is unlikely to be a significant increase in the number of people in specific populations taking a vitamin supplement unless a free or low cost vitamin D-only supplement is widely available. This may be particularly true for lower income groups. The PHAC also noted that there is little point in awareness-raising activities to promote vitamin D supplements if affordable supplements are not widely available.

The evidence reviews identified very little data on how existing guidance on vitamin D supplements has been implemented. The evidence available tends to be relatively poor and usually focuses on groups targeted by the Healthy Start initiative. No evidence was identified for interventions aimed at increasing the uptake of vitamin D supplements among: people aged 65 or older, people who have low or no exposure to the sun, or people who have dark skin. In addition, only very limited information was available on the views of those taking supplements or in specific population groups. The effectiveness of specific interventions was also difficult to determine. For example, it was difficult to quantify the relative impact of: training for health professionals; making vitamin D or Healthy Start supplements more widely available (including the impact of cost); and activities to increase awareness of the importance of taking them among specific population groups.

The evidence on the implementation of existing vitamin D guidance was very limited. As a result, following discussion with PHAC, NICE commissioned an additional review of reviews on effective implementation of a range of public health and clinical guidelines. Several key themes emerged. For example, the PHAC noted that implementation of any health intervention is likely to be more effective if health professionals are made aware of the issue and are prompted to raise it. Other 'effectiveness' factors include consistent guidance and advice and simple, inexpensive interventions.

The PHAC noted the importance of ongoing monitoring and evaluation of the availability and uptake of vitamin D supplements among specific population groups, at a national and local level. Members were also aware that data collection may involve using limited resources. Nevertheless, monitoring and evaluation appears to have been insufficient and inconsistent to date and there has been little opportunity to learn from good practice.

The limited evidence available points to extremely low uptake of Healthy Start supplements among eligible pregnant and breastfeeding women and children younger than 4 years. One study of 13 primary care trusts across all regions of England reported uptake to be below 10% (Jessiman et al. 2013). Another reported it to be less than 3% (Moonan et al. 2012). Variation between areas suggests that action can be taken to improve uptake. (For example, members discussed increasing the number of outlets providing the supplement and providing training for health professionals.)

The PHAC was aware that uptake of Healthy Start vouchers for infant formula, cow's milk and fruit and vegetables was good (at around 77% of those eligible) (Jessiman et al. 2013). Members noted that this could be because the voucher can be used at a variety of outlets as part of everyday shopping.

The PHAC discussed the need to give people eligible for Healthy Start support a clear explanation of the different benefits gained by taking Healthy Start supplements and consuming the milk, fruit and vegetables provided. Members were concerned that users of the scheme may be unaware of the importance of taking the supplement.

The PHAC was aware that numerous aspects of the system for distributing Healthy Start vitamins may hinder implementation. For example a report commissioned by the Department of Health's Policy Research Programme Healthy start: understanding the use of vouchers and vitamins identified that senior public health practitioners may spend considerable time administering the scheme. In addition, the order and reimbursement processes are slow and complex, and there are ongoing concerns about shelf-life and storage. The study's authors also reported that the voucher format and the process for getting supplements are confusing for the public.

The PHAC discussed the fact that universal free provision of Healthy Start vitamins can improve uptake, but that without wider action the impact may be limited. One study suggests uptake may almost treble with universal free provision, but only to around 4% for children's drops and 7.7% for women's tablets. Another study showed a year-on-year increase in uptake to 23% for women's tablets and 20% for children's drops when universal free supplementation was supported by action to increase awareness (McGee and Shaw 2013). No studies were identified that compared universal free provision of vitamin D supplements with universal provision of supplements that have to be paid for (albeit at a low cost). This prevented the committee from commenting on the relative benefits of these approaches and members felt that this is an important area for future research.

The PHAC was concerned that most mothers and children at risk of vitamin D deficiency are not eligible for the Healthy Start scheme. The lack of a similar alternative, or the cost of commercial supplements, may deter them from taking a supplement (particularly those from lower income groups). Some areas had made local arrangements to sell Healthy Start vitamins. But health and social care legislation, introduced in April 2013, means this is no longer possible. Furthermore, the Department of Health's existing arrangements with manufacturers mean it is not possible to get Healthy Start supplements from many places where people might expect to find them. (For example, they are not available in high street or supermarket pharmacies.)

The PHAC agreed that health, social care and other practitioners in contact with specific population groups need training to provide robust, consistent advice – and that this is essential if vitamin D supplementation is to increase. But members also recognised that this would have limited impact if the availability of supplements and inconsistencies in current guidelines are not resolved.

The main question asked in the economic model was: 'What is the most cost‑effective way of providing vitamin D supplements to specific population groups?'. Because of the focus of the guideline, 'What is the cost effectiveness of vitamin D supplementation among specific population groups?' was a subsidiary question for pregnant and breastfeeding women, and for children under 5 years. Modelling was based on 4 specific population groups: pregnant women and breastfeeding women, children aged under 5 years, people aged 65 or over and people whose skin is darker. There were not enough data to model this question for 'people whose skin is not sufficiently exposed to the sun'. (We do not know how many people in the population this affects, nor the extent of the deficiency among this group.) The cost of giving everyone in each group a daily supplement was compared with the cost of testing everyone and giving vitamin D supplements only to those with an identified deficiency. The model included estimated costs of intervention administration and delivery, based on an intervention in Birmingham (McGee and Shaw 2013).

The economic model found that it is cost saving to give everyone in each group a daily vitamin D supplement, rather than testing them all and supplementing only those who are deficient. It was assumed that the cost of a test is fixed at £16.50.

A potential limitation of the modelling analysis is that it assumes everyone is given a prophylactic supplement without being tested. This may mean that less emphasis is given to finding people who are severely deficient and who may need a higher dose of vitamin D. However, people showing the symptoms of severe deficiency may well be tested. Aspects of this situation are explored in a sensitivity analysis in the cost effectiveness report. The model did not consider any risks associated with taking a supplement containing the reference nutrient intake for vitamin D. The PHAC agreed that there is a negligible risk associated with taking the prophylactic dose.

The subsidiary analysis looked at increasing the uptake of vitamin D supplements among pregnant and breastfeeding women and children aged 5 years and younger. The estimated cost of supplementation for each additional woman who is pregnant or breastfeeding was £10.15. This resulted in an estimated cost per deficiency averted of £2859. For children aged 5 or younger, the estimated cost of supplementation per additional child was £4.62. This resulted in an estimated cost per deficiency averted of £1229.

A limitation of the subsidiary analysis (see 4.19) is that people with a vitamin D deficiency are defined in the model in terms of the symptoms of deficiency, rather than by their vitamin D status. So if someone had a low vitamin D status but did not show any symptoms of deficiency, the model assumed they would not benefit from a supplement. Because people with symptoms of deficiency are likely to be a relatively small subset of those defined as having a low vitamin D status, the model almost certainly overstates the cost of averting a 'deficiency'.