Got the winter blues? It could be because you didn't top up with enough vitamin D during the sunny summer months.
There's a link between vitamin D levels, which we mainly get from exposure to strong sunlight, and SAD, or seasonal affective disorder.
The vitamin may act as a regulator and controls whether or not we develop SAD during the winter months, a problem that affects around 10 per cent of the population, say researchers from the University of Georgia.
Having looked at more than a hundred papers that researched SAD, the researchers believe that our levels of vitamin D are a determining factor. Several papers discovered a time lag of around eight weeks between the end of the summer and the start of SAD, and that is roughly the time the body needs in order to process the UV radiation rays from the sun. Other studies have shown that depressed people have low levels of vitamin D.
The researchers say it is important to expose the skin-without sun cream-for several minutes every day during the summer months.
(Source: Medical Hypotheses, 2014; 83: 517)