Vitamin D is essential for skeletal growth and bone health. Dietary sources in the UK are very limited and oily fish is the only significant source. Small amounts are provided by egg yolk, red meat and fortified foods, such as formula milks for infants and toddlers, some breakfast cereals and fat spreads (margarine). The major natural source is from skin synthesis following exposure to sunlight.
From October to the beginning of April in the UK there is no ambient ultraviolet sunlight of the appropriate wavelength for skin synthesis of vitamin D. During this time, the population relies on both body stores from sun exposure in the summer and dietary sources to maintain vitamin D status (Scientific Advisory Committee on Nutrition's update on vitamin D 2007).
The National Diet and Nutrition Survey: results from Years 1 to 4 (combined) of the rolling programme for 2008 and 2009 to 2011 and 2012 (Public Health England and Food Standards Agency) shows that vitamin D status is highest among all age groups in the summer months and lowest in the winter. For example, only 8% of adults aged 19–64 had a low vitamin D status in July to September, compared with 39% in January to March. Similarly, around 2% of children aged 4 to 10 years had a low vitamin D status in July to September, compared to 32% in January to March.
Severe vitamin D deficiency can result in rickets among children: there has been concern that rickets may be re-emerging among children in the UK (Pearce and Cheetham 2010). It can also result in osteomalacia (soft bones, among children and adults) and hypocalaemia (low levels of calcium in the blood) in children. In addition, low vitamin D status has been associated with some diseases and other long-term conditions such as osteoporosis, diabetes and some cancers, although the evidence is inconclusive (Update on vitamin D).
The National Diet and Nutrition Survey suggests that almost a fifth of UK adults have a low vitamin D status. This means they have less than 25 nmol/litre of the main circulating form of vitamin D in their body – 25 hydroxyvitamin D (25[OH]D) ('National Diet and Nutrition Survey: results from Years 1 to 4 (combined) of the rolling programme for 2008 and 2009 to 2011 and 2012').
A newborn baby's vitamin D status is largely determined by the mother's level of vitamin D during pregnancy.
Breast milk is not a significant source of vitamin D. Formula milks for infants have to be fortified with vitamin D (this is voluntary for formula milks for toddlers).
Infants who are exclusively breastfed, or have less than 500 ml a day of infant formula, may not get enough vitamin D to meet their needs. (See NICE guidance on antenatal care and maternal and child nutrition.) Infants from Asian families are at particular risk. The Asian Feeding Survey (Infant feeding in Asian families, 1994–1996 Office for National Statistics) found that up to a third of Indian, Bangladeshi or Pakistani children had low vitamin D status at age 2.
People with dark skin are at increased risk of deficiency as their skin is less efficient at synthesising vitamin D. In other words, they need to expose their skin to sunlight for longer to make the same amount of vitamin D as people with paler skin. People of African, African-Caribbean and South Asian family origin, and those who remain covered when outside, are at particular risk. Almost 75% of Asian adults may have low vitamin D status in the winter. (For more details see the expert paper Vitamin D intakes and status.)
Older people are also at increased risk, particularly if they are frail, because they may spend more time indoors and have limited sun exposure.
People who are housebound and others who have limited exposure to the sun all year round (for example, those in prison) are also at increased risk (the SACN update on vitamin D). For example, the National Diet and Nutrition survey suggests that between 10 and 20% of older adults have low vitamin D status. This can increase up to 38% among people living in institutions.
There is substantial variation in vitamin D status across England, with people living in more southerly regions tending to have a better vitamin D status. London is the exception.
The Health Survey for England (NHS Information Centre for Health and Social Care 2010) found that 35% of adults in London had low status compared to the national average of 24%. (For more details see the expert paper 'Vitamin D intakes and status'). This may reflect the higher number of people from the minority ethnic groups at risk of vitamin D deficiency living in London, compared to other parts of England.
All UK health departments (for example, see the 2012 Chief Medical Officers' report Vitamin D – advice on supplements for at risk groups) and NICE (see our pathways on antenatal care and maternal and child nutrition) have issued evidence-based guidance on vitamin D supplements for various population groups. They have also provided guidance on how to distribute free Healthy Start supplements (that contain vitamin D) to eligible families.
The 4 UK chief medical officers have also flagged that health professionals could make 'a significant difference' if they ensure those at risk of vitamin D deficiency understand how important the vitamin is and how to get a daily supplement. They say that all at‑risk groups should be made aware of how they can obtain the vitamins locally ('Vitamin D – advice on supplements for at risk groups').
The Chief Medical Officers also stress the need to ensure people who may be eligible for the Healthy Start scheme know how they can apply. Note: this scheme provides vouchers that can be used to buy infant formula, cow's milk and plain fresh or frozen fruit and vegetables. People also receive coupons that can be exchanged for vitamin supplements that include the recommended amounts of vitamin D.
Evidence suggests implementation of these recommendations has been limited ('Vitamin D – advice on supplements for at risk groups'). For example, a report commissioned by the Department of Health's Policy Research Programme (Healthy start: understanding the use of vouchers and vitamins) found that parents find it difficult to access Healthy Start vitamins, health professionals do not promote the scheme and eligible families are often unaware of it. It also found that the distribution system is complex, confused and weak, and mothers are not motivated to take the vitamins or to give them to their children.
The cost effectiveness of implementing interventions to prevent vitamin D deficiency also remains unclear. Testing for vitamin D insufficiency has been reported to have increased 2- to 6-fold in recent years and, at approximately £20 a test, is likely to be a considerable cost for the NHS (Sattar et al. 2012). Primary care spending on treatments for vitamin D deficiency rose from £28 million in 2004 to £76 million in 2011 (Treating vitamin D deficiency GP, 13 February 2012; Prescription cost analysis England 2011 Health and Social Care Information Centre). In 2006, it cost an estimated £2500 to treat each child identified with symptomatic vitamin D deficiency (Zipitis et al. 2006).
Supplements containing vitamin D are available on prescription or for sale from pharmacies or shops. However, there is wide variation in the content and price and some supplements may not be suitable for particular at‑risk groups. (For example many multivitamins contain vitamin A, which pregnant women should avoid during pregnancy.)
Healthy Start vitamins tend to be available from health clinics, children's centres, Sure Start centres, outreach programmes or GP surgeries, although there have been national and local supply problems. Manufacturers have not made them directly available to pharmacies.
In 2013, the Chief Medical Officer for England recommended a review of the cost effectiveness of extending the provision of free Healthy Start vitamins to every child. This was due to concerns that 'providing free vitamins to targeted groups has not led to high enough levels of uptake' (CMO's annual report 2012: our children deserve better Department of Health).
Up to April 2013, people not eligible for Healthy Start were able to buy the supplements at a much lower cost than commercial preparations. However, this option was encouraged in only a limited number of areas (Help pregnant women, new mothers and children get their free healthy start vitamins Department of Health). Since April 2013, following a change in health and social care legislation, these supplements can no longer be sold.