Friday January 22 2010
Rickets was common in the UK during the Victorian era
“The many hours children spend indoors playing computer games or watching television may be to blame for a resurgence of rickets,” The Times reported. Several newspapers also covered this research on vitamin D deficiency in the UK.
The news stories are based on a narrative review of the evidence for the diagnosis and management of vitamin D deficiency. Many newspapers focused on a single quote by the lead author that “kids are staying indoors playing on computers rather than going outside to kick a ball around”.
However, it is important to highlight that this is not new research, but the opinion of these authors. The review did not look at the use of TV or computer games, and does not provide any new evidence of a link between these and rickets.
The authors highlight the importance of sunlight to ensure that the body has enough vitamin D, but they also mention other risk factors for vitamin D deficiency, one of which is having dark skin. As the researchers point out, it is possible that the increase in cases of rickets reflects the changing ethnic mix in the UK.
The increasing numbers of children with rickets in the UK suggests that more needs to be done in terms of prevention. How this will be done will need further research and discussion. Advice about sensible sun exposure remains the same.
Where did the story come from?
The review was written by Drs Simon Pearce and Tim Cheetham from Newcastle University and the Royal Victoria Infirmary. No funding was received for this study, which was published in the peer-reviewed British Medical Journal.
This story is covered by several news sources, most of which focus on the quote by the lead researcher that “kids are staying indoors playing on computers rather than going outside to kick a ball around”. The author’s comment must be considered in the context of his article, which is a discussion of the range of risk factors for vitamin D insufficiency and deficiency. This is not new research into the potential association between vitamin D levels and indoor activities such as playing computer games or watching TV.
What kind of research was this?
The news reports are not based on new original research, but on a narrative clinical review in which the authors discuss the evidence around the diagnosis and management of vitamin D deficiency, and the issues that this raises for the general population. The authors describe it as a discussion of the “diagnosis of vitamin D insufficiency and deficiency in children and adults according to evidence from descriptive and observational studies, randomised trials and meta-analyses”.
What are rickets and osteomalacia?
Rickets and osteomalacia are caused by profound vitamin D deficiency. These conditions are characterised by weak bones. Rickets, a childhood disease that can affect developing bones, often occurs in children who are suffering from severe malnutrition in the early stages of their childhood.
Vitamin D is important for bone health because it promotes the absorption of calcium and phosphorous. These minerals are needed to build strong, healthy bones. A deficiency of vitamin D makes it difficult to maintain bone strength and structure, which leads to weak, soft bones that can be deformed.
Osteomalacia is the adult version of rickets, in which vitamin D deficiency can lead to a softening of the bones as a result of problems in bone construction (it is different to osteoporosis, which weakens already formed bone).
What did the research involve?
The authors of this narrative review describe the results of a recent nationwide survey, which found that more than half of the adult population in the UK have insufficient levels of vitamin D. Sixteen per cent have severe deficiency during winter and spring. The authors say that the recommended daily intake of vitamin D in the UK is 400IU for an adult, 280IU for children between six months and three years, and 340IU for children under six months. However, this is only enough to prevent rickets (in children) and osteomalacia (in adults). In the absence of skin synthesis of vitamin D (i.e. encouraged by sunlight and therefore reduced during the winter months), this recommended daily intake is not optimal. They conclude, therefore, that the low dietary vitamin D intake, combined with the lack of skin synthesis for half of the year, explains the “disturbingly high prevalence of vitamin D deficiency across the UK”.
The authors say that in a fair-skinned person, 20 to 30 minutes of daily midday sun exposure on the face and forearms is enough to generate the equivalent of about 2,000IU of vitamin D. Two or three such sunlight exposures a week are “sufficient to achieve healthy vitamin D levels in summer in the UK”. They acknowledge that people with pigmented skin would require a longer exposure time or greater frequency to get the same level of vitamin D as fair-skinned people.
The authors also discuss dietary sources of vitamin D, which may be particularly important in the winter months in the UK when there is less sunlight and therefore not enough UV light to synthesise the vitamin. They draw on several published studies that have linked low vitamin D in the blood (i.e. low levels of circulating 25-hydroxyvitamin D) to major negative health outcomes, such as overall mortality, death from cardiovascular causes, diabetes and cancer.
The authors go on to discuss the signs and symptoms of patients with vitamin D deficiency, the investigations that are necessary, and how rickets and osteomalacia should be treated. Treatment largely centres on replenishing vitamin D stores.
What were the basic results?
These are the authors’ summary points, taken directly from their article:
- Vitamin D insufficiency is common in the UK population.
- Vitamin D deficiency typically presents with bone deformity (rickets) or hypocalcaemia in infancy and childhood, and with musculoskeletal pain and weakness in adults.
- Many other health problems (including cardiovascular disease, type 2 diabetes, several cancers and autoimmune condition) have recently been associated with vitamin D insufficiency.
- Risk factors include skin pigmentation, use of sunscreen or concealing clothing, being elderly or institutionalised, obesity, malabsorption, renal and liver disease, and using anticonvulsants.
- Vitamin D status is most reliably determined by assay of serum 25-hydroxyvitamin D (25-OHD).
- Rickets and osteomalacia should be treated with high-strength calciferol (ergocalciferol or colecalciferol) for 8 to 12 weeks, followed by regular vitamin D supplements.
How did the researchers interpret the results?
The authors say that vitamin D deficiency and insufficiency are common in the UK. They say that a change in UK public health policy [in response to this] is long overdue.
The newspapers have focused on the importance of sun exposure and its relationship to vitamin D deficiency to highlight the general points being made by these two clinicians. Exposure to sunlight is important in ensuring that vitamin D levels in children are sufficient to prevent rickets, but the authors’ comment is not based on a new piece of research that has assessed the harms of indoor activities. Such research could, for example, compare the incidence of rickets in children watching TV or playing computer games with those who do not engage in such activities.
It is common sense that both adults and children should have regular exercise (many sports have the added benefit of sun exposure as they are played outside), alongside a healthy, balanced diet (which will provide dietary vitamin D) to maintain general health.
Importantly, the authors say that in the northern hemispheres, “the major risk factor for [vitamin] D insufficiency and deficiency at all ages is pigmented skin”. It is possible that the increase in cases of rickets as highlighted in this piece may reflect the changing ethnic mix in the UK. In fact, the authors go on to say that research in sunnier climates (e.g. Australia) has found that over the past 20 years, many of the children with vitamin D deficiency have consisted primarily of immigrant children or first-generation offspring of immigrant parents with dark skin. However, they also point out that a study in Denmark found that the problem is also present in ethnic Europeans.
The authors highlight several important issues regarding sun exposure. They say that sunscreens of SPF15 or higher, block more than 99% of skin synthesis of vitamin D, placing “individuals with fair skin at similar risk of vitamin D deficiency to those with pigmented skin”. However, excessive sun exposure is a risk factor for skin cancer.
Advice about sensible sun exposure should be followed. The risks of excessive exposure are well-established and should be avoided wherever possible, including avoiding sunbeds and getting sunburnt. Advice about ensuring adequate intake of vitamin D should also be followed, particularly by groups who may be at risk of vitamin D insufficiency or deficiency.