By Marc Sorenson, EdD, Sunlight Institute
After coming across some research having to do with sun exposure and the seasonality of fractures, I thought it wise to share it with my readers.
In high latitude areas, which have far less sun availability than lower latitude areas, we would expect rates of hip fracture to be high, and such is the case. Sweden is a country that has large differences in latitude, and in research performed there it was shown that the higher the latitude and the lesser the sun exposure, the greater was the risk of hip fracture. In other words, significantly more hip fractures occurred in the northern part of the country compared to the middle and southern parts. Another Swedish investigation demonstrated that in men, hip fracture risk was 37.5% lower in summer than winter. Women had a 23.5% reduced risk in summer.
Research from Norway showed similar results. Hip fracture risk in men was 40% higher in winter than summer, and in women the risk was 25% higher.These fluctuations in seasonal hip fractures indicate a loss of bone mass during periods of low sun exposure (winter) and an increase in bone mass during periods of high sun exposure (summer). In other words, sun exposure is able to reverse bone loss, or osteoporosis. Other studies show similar patterns of bone strength based on sun exposure or lack thereof.
The importance of sunlight in maintaining and producing strong bones has been known since antiquity. Dr. Richard Hobday, author of The Healing Sun, writes the following comments and a history in an online article. “Traditionally, sunlight deprivation has been linked with weak or brittle bones. One of the earliest references to this was made more than two thousand years ago by the Greek historian Herodotus (480-425 BC), who noted a marked difference between the remains of the Egyptian and Persian casualties at the site of battle of Pelusium which took place in 525 BC:
‘At the place where this battle was fought I saw a very odd thing, which the natives had told me about. The bones still lay there, those of the Persian dead separate from those of the Egyptian, just as they were originally divided, and I noticed that the skulls of the Persians were so thin that the merest touch with a pebble will pierce them, but those of the Egyptians, on the other hand, are so tough that it is hardly possible to break them with a blow from a stone. I was told, very credibly, that the reason was that the Egyptians shave their heads from childhood, so that the bone of the skull is indurated by the action of the sun — this is why they hardly ever go bald, baldness being rarer in Egypt than anywhere else. This, then, explains the thickness of their skulls; and the thinness of the Persian’s skulls rests upon a similar principle: namely that they have always worn felt skull-caps, to guard their heads from the sun.’ Herodotus, ‘The Histories’”
The message is this: Don’t hide yourself from the sun; rather, embrace it in a safe manner, and that will protect your bones.
 Nilson F, Moniruzzaman S, Andersson R. A comparison of hip fracture incidence rates among elderly in Sweden by latitude and sun exposure. Scand J Public Health. 2014 Mar;42(2):201-6.
 Odén A, Kanis JA, McCloskey EV, Johansson H. The effect of latitude on the risk and seasonal variation in hip fracture in Sweden. J Bone Miner Res. 2014 Oct;29(10):2217-23.
 Solbakken SM1, Magnus JH, Meyer HE, Emaus N, Tell GS, Holvik K, Grimnes G, Forsmo S, Schei B, Søgaard AJ, Omsland TK.
 Grønskag AB1, Forsmo S, Romundstad P, Langhammer A, Schei B. Incidence and seasonal variation in hip fracture incidence among elderly women in Norway. The HUNT Study. Bone. 2010 May;46(5):1294-8.
 Richard Hobday. The Healing sun: Sunlight, Brittle Bones, and Osteoporosis. http://sunlightenment.com/the-healing-sun-sunlight-brittle-bones-and-osteoporosis/. (accessed February 5, 2016)