This was an interesting post by John Briffa this month about some surprising benefits of sunshine on skin problems such as psoriasis (well known), but also on blood sugar and cholesterol levels. As he says at the end, perhaps there are deeper reasons why we come back from sunny holidays feeling better in ourselves…
“Vitamin D is made in the skin in response to sunlight, so one question we might ask is whether vitamin D might also somehow promote health here. One piece of indirect evidence which supports this concept relates to the experience that many sufferers of the skin condition psoriasis have in the sun. Psoriasis is characterised by raised, red, usually scaly skin ‘plaques’ (often on the knees, elbows and scalp). Quite often, these can improve considerably and may even disappear when exposed to sunlight, say when on holiday.
Psoriasis is thought to be caused by the excessive proliferation of cells in the outer layer of skin known as keratinocytes. Vitamin D regulates a large number of genes in the keratinocytes, which means that vitamin D might have a role to play in the regulation of the division of these cells. In fact, compounds related to vitamin D (vitamin D ‘analogues’, such as something known as calcipotriol) are sometimes used in the treatment of psoriasis.
Light therapy is also sometimes used to treat psoriasis. This can be provided by ‘sun lamps’ giving off ultraviolet B (UVB) light. But of course this might just come directly from the sun.
I was interested to read a recent study where the effect of sunlight on psoriasis was tested. 20 Swedish men and women (average age 47) were taken off for a 3-week break in Gran Canaria (an island in the Atlantic sea about 130 miles/210 km off the northwest coast of Africa) [1].
The severity of psoriasis in this group was measured using something known as the Psoriasis Area and Severity Index (PASI). Over the course of their time on Gran Canaria, PASI scores declined an average of about 73 per cent. There was no control group (a similar group not sunning themselves in Gran Canaria to compares these results too), but nevertheless, my feeling is that these results are impressive, and add at least some scientific support for the anecdotal experiences of many psoriasis sufferers.
However, this study did not look only at individuals’ responses to sunlight. The researchers also measured vitamin D levels. I was particularly interested in this, seeing as I recently discovered my own vitamin D levels were crashingly low, and one thing I am doing to remedy this situation is to get as much sun exposure as I can without burning. At the beginning of the study, the average vitamin D was 57.2 nmol/l (22.9 ng/ml). At the end of the study, levels had risen to an average of 104.5 nmol/l (41.8 ng/ml) – a rise of almost 83 per cent.
The researchers also measured blood fat levels and the level of a substance known as HbA1c (also known as glycosylated haemoglobin) which gives a measure of blood sugar control over the preceding 2-3 months. Over the course of the study, there was improvement in the ratio of supposedly ‘bad’ LDL cholesterol to supposedly ‘good’ HDL cholesterol. This would traditionally be regarded as a sign of reduced risk of cardiovascular disease. Levels of HbA1c fell too. All changes were statistically significant.
Of course, some of these changes might have been down, at least in part, due to changes in factors others than sunlight/vitamin D levels (such as diet). Though dietary change tends not to change these parameters very quickly. The speed of the changes suggests that non-dietary factors (e.g. sunlight) were more likely to be responsible for these positive changes.
This study demonstrates, I think, sun exposure really does have the capacity to improve skin psoriasis. Sufferers will be generally glad of this relief, not just because the condition can be unsightly, but because it can be uncomfortable too (the plaques can crack and bleed for instance). The study also shows that sunlight exposure can dramatically enhance vitamin D levels. It should be borne in mind that the study subjects were from Sweden, and are likely to have had fair skin (more vitamin D is made in fair skin in response to a given amount of sunlight than in darker skin).
Finally, sunlight (and maybe other factors) appeared to lead to positive changes in the biochemistry of these individuals with regard to blood fat and blood sugar levels.
People who go off on holiday to sunnier climes very often report feeling better at the end of it. For many, getting away from one’s routine and perhaps hectic and stressful life at home has a part to play here. However, it does seem that, through the action of sunlight, one of the reasons that people feel healthier at the end of a holiday is because they are healthier. It seems to me that there is really is such a thing as a healthy tan.” John Briffa May 09.
References:
1. Osmancevic A, et l. Effect of climate therapy at Gran Canaria on vitamin D production, blood glucose and lipids in patients with psoriasis. J Eur Acad Dermatol Venereol. 24th April 2009 [Epub ahead of print publication]