Friday December 17 2010
Several newspapers have reported on new advice for sun exposure and vitamin D. Vitamin D is necessary to absorb calcium and form healthy bones. However, too much sun also raises the risk of skin cancer. Several large UK health organisations have made a joint statement about how much sun exposure would boost health without putting people at risk of its damaging effects.
The statement does not specify exactly how long people should aim to be in the sun for. This is because the time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors and may vary between individuals. The authors say that the time required is “typically short and less than the time needed to redden or burn”. Regularly going outside for a few minutes around the middle of the day without sunscreen is suggested as best and that “the more skin that is exposed the greater the chance of producing sufficient vitamin D before burning”. Importantly, this advice applies in the UK, and not necessarily in hotter climates.
Newspapers report that in practice this means between “10 and 15 minutes in the UK summer sun, without sunscreen several times a week is probably a safe balance between adequate vitamin D levels and any risk of skin cancer”.
Who gave the advice?
The advice comes from a group of seven British health organisations, which have issued a “consensus statement”, of their unified views.
The charities include the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society.
Why has the advice been issued?
Vitamin D, a vitamin necessary for health, is mainly obtained from sunlight. However, too much sun exposure has also been associated with the risk of skin cancer. Over the years, confusion may have grown from the advice issued by various organisations about the ideal levels of sunlight. The announcement from these seven organisations is aimed at clearing up some of this confusion.
A spokesperson for Cancer Research UK, said:
"This joint consensus statement brings together the latest evidence on vitamin D. In representing the unified views of many different organisations, we hope to provide some clarity around this important but controversial issue. It is encouraging that our stance agrees with that of other international organisations, such as the World Health Organisation and the US Institute of Medicine.”
How do I get vitamin D?
Most of a person’s vitamin D is made in their body through exposure to sunlight. The report says that the time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors, but is typically short and less than the amount of time needed for skin to redden and burn. Enjoying the sun safely, while taking care not to burn, can provide the benefits of vitamin D without unduly raising the risk of skin cancer.
Vitamin D supplements and specific foods can help to maintain sufficient levels of vitamin D, particularly in people at risk of deficiency. However, there is still a lot of uncertainty around what levels qualify as “optimal” or “sufficient”. There is also some uncertainty over how much sunlight different people need to achieve a given level of vitamin D, whether vitamin D protects against chronic diseases such as cancer, heart disease and diabetes, and the benefits and risks of widespread supplementation.
How much vitamin D does a person require?
How much vitamin D a person has in their body is best shown by measuring the level of 25-hydroxyvitamin D (25(OH)D) in their blood. There is a general consensus that levels below 25nmol/L (10ng/ml) are “deficient”. However, there is currently no standard definition of what the optimal level of vitamin D is, and vitamin D levels can vary between individuals.
Some scientists suggest that 70-80nmol is best, but others suggest that vitamin D levels may plateau at this level and not get any higher regardless of how much sunlight or supplements are taken. The report cites a Hawaiian study, which found that “half of healthy young surfers had levels below 75nmol/L despite extensive unprotected outdoor exposure and tanned skin”. Vitamin D can also be obtained through the diet, particularly through oily fish. However, estimates suggest that 90% of the vitamin D requirement comes from sunlight.
What about vitamin supplements?
The Department of Health currently recommends a daily 10microgram vitamin D supplement for people at risk of vitamin D deficiency, including pregnant and breastfeeding women, older people and people who may not have adequate sun exposure, such as those who are confined indoors or cover their skin for cultural reasons. Vitamin D is present in a range of dietary supplements (which are unlicensed) including fish oil products such as cod liver oil. Supplements that also contain vitamin A (including cod liver oil) are unsuitable for older people and pregnant women.
For most people however, the benefits and risks of taking vitamin D supplements are unclear. The report suggests that there is still a lack of evidence about the risks of “chronically raising” the populations levels of vitamin D through supplementation.
The report did not include figures of the estimated proportion of the UK population that is deficient in vitamin D.
How much sun should I aim to get?
The report says that ultraviolet B (UVB) radiation is the best way to boost vitamin D, but that it is unclear how much sunlight is needed to raise blood levels to a particular level. According to the report, environmental and personal factors affect vitamin D production in the skin making it difficult to make a “one size fits all” recommendation for the whole population. For example, the area of skin exposed to the sun will influence the amount of vitamin D that is made.
The report says that during the winter months in the UK, there is not enough UVB for the body to make vitamin D. Therefore, the body relies on stores of vitamin D and vitamin D obtained through the diet.
The report quotes data from a study in which caucasian British people were given a dose of simulated sunlight equivalent to midday summer sun for 13 minutes, three times a week for six weeks during the winter months. The participants were dressed in typical summer clothes that revealed a third of their skin. This raised vitamin D blood levels to more than 50nmol/L in 90% of people, and to more than 70nmol/L in 26% of people.
This study appears to be the basis for the recommendation of 10-15 minutes midday summer sun quoted by the newspapers. It is important to point out that the report did not actually specify a recommended time that people should spend in the sun again highlighting that the time required may vary dependent on clothing, the amount of shade, how much time people typically spent outside and so on. They said “regularly going outside for a matter of minutes around the middle of the day without sunscreen should be enough”.
What about sunbeds?
Sunbeds were not recommended as a way to top up vitamin D. Alongside UVB, sunbeds emit UVA which can cause skin cancer and does not contribute to vitamin D production.