Seasonal affective disorder (SAD) is a type of depression that starts in sufferers as the days get shorter in autumn and resolves or improves as the days get longer again in spring. The cause(s) of SAD are not fully understood but it is thought to be linked to the reduced exposure to sunlight and light treatment can be very effective.
There is also some research that suggests that supplementation of vitamin D may be effective for some sufferers of SAD, as well as of other types of depression. Vitamin D is interesting in that, unlike other vitamins, we can actually produce it ourselves in the skin under the influence of UV radiation. In fact sun exposure is our main source of vitamin D. However, as we tend to spend more and more time indoors and due to the fear of skin cancer put on high sunscreens when we are exposed to sun, vitamin D deficiency appears to be quite common, affecting up to a third of the adult population. People with dark skin, who do not go outside much or cover up for cultural reasons are most at risk.
The richest dietary source of vitamin D is oily fish, such as salmon, mackerel and sardines. Eggs, dairy products and meat also contain some vitamin D but not enough to prevent deficiency if they are the only source.
If you do suffer from SAD it might be worth having your vitamin D levels checked through a blood test and if you are found to be deficient supplementation may be beneficial.
by Dr Karin Elgar
