The sun has been worshipped as a deity; viewed as a symbol of ultimate power and the source of all health; inspired elaborate religions and dangerous cults. Synonymous with goodness and happy endings, it permeates our languages with platitudes and metaphors connoting health, wealth, wisdom and happiness. Whether we are comparing our true love to a summer's day, riding off into the sunset, or just have a "sunny disposition", the super star at the centre of our solar system is perennially typecast as a smiling symbol of well-being. This gaseous gargantuan fireball is essential for life on earth as we know it, and increasingly we are coming to appreciate some of the more subtle ways in which it contributes to our health and happiness.
It is widely known that adequate quantities of various vitamins and minerals are integral to maintaining good health. Ideally we achieve our requisite doses of these vitamins and minerals through a balanced diet. One vital vitamin, however, vitamin D, is relatively scarce in foodstuffs and our primary source of it comes directly from the sun. Sometimes referred to as the sunshine vitamin, vitamin D is photosynthesised through our skin's absorption of UV-B radiation from the sun.
It has long been known that vitamin D is essential for the maintenance of bone integrity. However the recent discovery that almost all cells in the body express vitamin D receptors has unveiled a plethora of other functions, suggesting a protective role for the sunshine vitamin against osteoporosis (bone disease), diabetes, rheumatoid arthritis, cardiovascular diseases, hypertension, multiple sclerosis, some common forms of cancer, and certain life-threatening bacterial infections like tuberculosis.
A lack of vitamin D is referred to as hypovitaminosis D, or vitamin D deficiency, and is known to be widespread in western populations, particularly among the elderly and the housebound. In one study of nursing home residents the prevalence of vitamin D deficiency was a staggering 58 per cent. One reason proposed for this widespread deficiency is the lack of opportunity for routine sun exposure in many of today's modern industrialised societies: anyone who has worked a 9-to-5 office job in the UK during the winter months will appreciate the feeling of going to, and from, work in what seems like a perpetual darkness.
Now there is emerging evidence that vitamin D deficiency may also be becoming a significant public health concern in nations that enjoy abundant year-round sunshine. For example, one UAE study of Emirati mothers and their infants reported an elevated prevalence of vitamin D deficiency in both mothers and babies. Findings suggestive of widespread vitamin D deficiency have also been reported within other Gulf nations; studies in Saudi Arabia and Kuwait confirmed a high prevalence of vitamin D deficiency among their citizens. Given the significant physical health problems associated with vitamin D deficiency, these findings give us cause for concern, and certainly warrant further, more robust epidemiological research being undertaken in the region. In addition to the focus on physical health, scientists have more recently also begun to explore the links between the sunshine vitamin and psychological health, particularly its relationship with depression. Epidemiological data from Europe and the US suggest a seasonal pattern for depression, with a definite spike in the winter. Interestingly, depression specific to wintertime (but not summertime depression) has been found to be responsive to light therapy; this is where a depressed person sits in front of a special bright light for 15 to 30 minutes per day. One explanation for this seasonal variation in mood states is that there is a link between vitamin D and depression. Some theorists go further still, suggesting that the recent rise in depression globally is partially explicable in terms of lower vitamin D levels as a consequence of our modern cities and lifestyles that increasingly keep us out of the sunshine.
Several studies have demonstrated a robust association between low vitamin D levels and mood disorders, most notably major depressive disorder. Similarly, cross-sectional studies comparing depressed patients with non-depressed controls found a higher prevalence of vitamin D deficiency in the depressed group relative to the control group. Several intervention studies have also shown promising results for the use of vitamin D supplementation as a treatment for depression. The role of vitamin D in the brain is at present poorly understood; however studies in animals have shown that severe vitamin D depletion in pregnant rats results in pronounced brain abnormalities in their offspring, suggesting a clear association between brain development and vitamin D. In short, there is mounting evidence that the sunshine vitamin also plays an important role in psychological health too.
Paradoxically, despite the year-round sunshine we experience here in the UAE, we too may be experiencing the consequences of vitamin D deficiency. Our modern lifestyles, disproportionate skin cancer anxiety, a scarcity of vitamin D-fortified foodstuffs, the widespread belief that fair skin is prettier than tanned skin, and numerous other socio-cultural factors may all be contributing to unhealthily low levels of the sunshine vitamin. We presently have a nationwide study under way to look at these issues in greater detail. The findings, we hope, will help us better target public health initiatives aimed at preventing this insidious health problem. Dr Justin Thomas is a psychologist in the Department of Natural Science & Public Health at Zayed University Dr Fatme Al Anouti is a biochemist in the Department of Natural Science & Public Health at Zayed University