Many people believe that rickets (soft bones and other developmental problems) is no longer a problem, but it has shown up again in children who are breast-fed and dark-skinned. Up until 1920, rickets was common. It's caused by lack of vitamin D.

Rickets was caused by the industrial revolution with thick clouds of dust and people working 18 hours a day, and even when they got outdoors, the dark clouds prevented them from get sun. In 1822, physicians in Warsaw showed that children in the suburbs didn't get rickets, while those in the city did. Children in the farms got sunlight, children in the city did not.

In 1913, Hans Steenboick at the University of Wisconsin showed that lactating goats kept indoors got rickets, while those let outside did not. In 1923, Elmer McColum at Johns Hopkins showed that cod liver oil prevented rickets. Now we had to explain why sunlight and cod liver oil prevent rickets. 1924, Adolf Windaus in Gottingen, Germany isolated the chemical that prevents rickets and it was called vitamin D. 1931, Michael Holick at the Massachusetts General Hospital showed that vitamin D3 was produced by sunlight on the skin. The darker the skin, the more exposure to sunlight is needed to get enough vitamin D.

Humans rarely get enough vitamin D from food, so they have to depend on sunlight to make it in their skin. The reason we are seeing Vitamin D deficiency today is that many people do not get enough sunlight because they are brought up in cold weather climates, or avoid sunlight because of fear of skin cancer, or spend all their time indoors. So now doctors are seeing rickets where mothers lack vitamin D, breastfeed, protect their infants from sunlight, and do not use vitamin supplements.

 

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