Vitamin D and its role in preventing and treating seasonal affective disorder (SAD)

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The dwindling daylight hours that inevitably come at this time of year are usually viewed with some dread by sufferers of seasonal affective disorder (SAD) – a condition in which a shortage of sun can provoke anything from dark moods to full-blown depression. In addition to the light relief offered by increased exposure to the sun or sunlight-simulating devices, those afflicted with SAD may also be advised to take conventional antidepressants. It seems that such drugs no longer require a prescription, now it has been revealed that Prozac is to be found in the mains water supply. I suppose it’s always possible that some sufferers of SAD may be happy to learn that the nation’s favourite antidepressant is now available on tap.

Those looking to lighten up their mood during the darker months more naturally might be interested in research which suggests that SAD may respond to a nutritional approach. For a long time it has been known that one effect of the sun’s rays is to stimulate the production of vitamin D in the skin. More recently, an increasing body of research has amassed which suggests that this nutrient has important roles to play in the brain. These basic facts have led scientists to test whether supplementing with vitamin D might help lift the symptoms of SAD.

In one such study, just five days of treatment with vitamin D (at a dose of 400 or 800 IU per day) was found to improve winter mood. In another piece of research, the mood of SAD sufferers was found to improve more in individuals treated with a single dose of 100,000 international units (IU) of vitamin D than in those treated with light therapy. Further evidence for the potential for vitamin D to alleviate SAD came from research published earlier this year. In this study, individuals were treated with either 600 or 4000 IU of vitamin D each day for at least six months. Both dosages of vitamin D led to improvements in the participants’ mood and general well-being, with those on the higher dose of vitamin D benefiting the most.

This research may have particular relevance to Britons, as recent research has revealed that a quarter of us suffer from vitamin D deficiency in the winter. Those wanting to maintain good levels of vitamin D will find useful quantities of this nutrient in prawns and oily fish such as sardines, mackerel and salmon. Individuals with a tendency to winter depression may do well to have their vitamin D levels assessed, something that is best done by measuring something known as 25-hydroxy vitamin D in the blood. Ideally, levels of this should be above 35 nanograms per ml (87 nanomoles per litre).

SAD sufferers with low levels of vitamin D may benefit from supplementing with cod liver oil, as each teaspoon of this contains about 400 IU of vitamin D. I generally recommend that one or two teaspoons of cod liver oil be taken throughout the winter. Larger doses should be taken under medical supervision. Those preferring to supplement with vitamin D itself should be aware that this nutrient comes in two main forms: cholecalciferol (also known as vitamin D3) and ergocalciferol (vitamin D2). Cholecalciferol is generally taken to be the more potent and preferred form of vitamin D. Ensuring a good intake of this nutrient may help keep those prone to SAD from experiencing a winter of discontent.

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