“I think the future of health is everybody having something you can carry round that takes your specific factors into account.” —Rob Williams, creator of D Minder.

In the grey winter months, many of us are affected by loss of energy and plummeting moods: the ‘Winter Blues’, a phenomenon long-observed but only recently classified as S.A.D.

In certain areas of America, up to 1 in 10 people is thought to suffer from the condition, but it’s only been within the past decade that its origins—namely, vitamin D deficiency through lack of sunlight—have come to be better understood.

Software developer Rob Williams grew up in New Jersey, and found himself suffering from depressive spells after prolonged periods of cold, grey weather. After a move to sunny California changed his life, he decided to develop a free app that would help other individuals to roughly calculate the amount of vitamin D they were receiving in their daily lifestyle.

D Minder is free to download from the app store.