At the time of writing this blog post, we have had the first glorious sunny Spring days of the year after a definitely dreary, soggy few months. And of course, we’re all feeling a bit better with the brighter days.
As usual, patients always ask how much sun exposure is safe.
Is sun exposure safe?
Our advice nowadays is that you do need some sun to make Vitamin D and protect your bones and this can generally be obtained with 20 minutes of unprotected sun exposure per day but NOT to a level where the skin turns pink or brown.
Can sun exposure do more than that?
There have been suggestions that sun exposure might be associated with a lower incidence of cardiovascular diseases together with other diseases such as chronic obstructive pulmonary disease (COPD) and diseases of the digestive tract and pancreas, such as diabetes.
[ReichrathJ. The challenge resulting from positive and negative effects of sunlight: how much solar UV exposure is appropriate to balance between risks of vitamin D deficiency and skin cancer? Prog Biophys Mol Biol 2006; 92: 9-16]
[Jensen AO, Bautz A, Olesen AB et al. Mortality in Danish patients with nonmelanoma skin cancer, 1978-2001. Br J Dermatol 2008; 159:419-25.]
Also, there was a publication in September of last year in the International Journal of Epidemiology which suggested beneficial effects of sun exposure beyond just Vitamin D and osteoporosis.
[Brøndum-Jacobsen P, Nordestgaard BG, Nielsen SF et al. Skin cancer as a marker of sun exposure associates with myocardial infarction, hip fracture and death from any cause. Int J Epidemiol 2013; 1-11.]
What did the paper show?
The study was performed in Denmark and looked at the entire Danish population above the age of 40 years from 1980 to 2006 who were on national registers as having had a melanoma, other skin cancers that were not melanomas (or nonmelanoma skin cancers or NMSC), heart attacks (myocardial infarction or MI), hip fracture or death from any cause. This comprised 4.4 million people!
And what were their results?
The study showed that the incidence of MI and hip fracture was lower amongst individuals with skin melanoma and those with NMSC than those without. The incidence of death from any cause was also lower amongst individuals with NMSC (but not cutaneous melanoma).
Oh my goodness!
Well, the authors do concede that they are taking skin cancer as a marker of sun exposure. Not all individuals when exposed to the sun will develop skin cancers. They also haven’t taken smoking status into account either.
They also speculate that there is an association with increased sun exposure and more outdoor physical activity and increased physical activity is linked with lower risks of cardiovascular disease and osteoporosis, to name a few.
[Haennel RG, Lemire F. Physical activity to prevent cardiovascular disease. How much is enough? Can Fam Physician 2002; 48: 65-71.]
[Schmitt NM, Schmitt J, Doren M. The role of physical activity in the prevention of osteoporosis in post-menopausal women – An update. Maturitas 2009; 63: 34-38.]
The authors freely admit that in their own study, the lowest risk of MI and death from any cause is in those individuals with a high level of occupational physical activity.
Is the benefit due to Vitamin D?
The authors do touch upon this.
There have been some epidemiological studies (large studies looking at populations) that have shown an association between high levels of Vitamin D and lower cardiovascular mortality but randomized controlled trials (the Gold Standard for trials) have shown no effect of Vitamin D supplementation on risk of cardiovascular mortality.
[Parker J, Hasmi O, Dutton D et al. Levels of vitamin D and cardiometabolic disorders: Systematic review and meta-analysis. Maturitas 2010; 65: 225-36.]
[Judd SE, Tangpricha V. Vitamin D deficiency and risk for cardiovascular disease. Am J Med Sci 2009; 338: 40-44.]
The studies looking into Vitamin D and hip fractures are equally ambiguous. However, the combination of Vitamin D and calcium supplementation does lower the risk of hip fracture.
[Abrahamsen B, Masud T, Avenell A et al (The DIPART group). Patient level pooled analysis of 68 500 patients from seven major vitamin D fracture trials in US and Europe. BMJ 2010; 340: b5463.]
So where do we go from here?
The authors postulate that sun exposure does have its benefits, which we can all appreciate, especially when we have been deprived of it for months.
As to whether we can now advise people to seek the sun? I’m not sure we can do that beyond the 20 minutes a day recommended above. There clearly needs to be more studies looking into the beneficial effects of sun exposure.
Regards,
Sandy
Dr Sandy Flann, Consultant Dermatologist.
