Sunlight (especially UVB) is required to covert 7-dehydrocholesterol to previtamin D3 in the skin. Inadequate exposure to sunlight can result in rickets or osteomalacia depending on the age of the patient.

Risk factors for insufficient light exposure:

(1) dark skinned individuals (require more sun exposure than someone with fair skin)

(2) long winters with little sunlight (polar latitudes; days are shorter and less UVB light occurs)

(3) dense jungle or prolonged periods with an overcast sky

(4) sleep during the day (night owls)

(5) those who never go out (chronically ill, prisoners or elderly recluses)

(6) obese (deposit vitamin D3 into fat stores)

(7) constant sunscreen usage

(8) patients who avoid sunlight because of its damaging effects (phototoxicity, albinism)


A person with one or more of these risk factors should be screened for rickets or osteomalacia.

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