Table 1.

Risk factors for vitamin D deficiency

Lack of sun exposure5Reduced skin synthesis
Latitude of residence6No skin synthesis November to March at 52° north (eg, Edmonton, Alta)
Sunscreen use7SPF of 15 blocks 99% of skin synthesis
Urbanization8Increasing time indoors and increased automobile use
Aging975% reduction in skin production by age 70; increased institutionalization as a greater percent of the population ages
Increased chronic disease prevalence10Reduced sun exposure due to increased time indoors; some chronic conditions contribute physiologically to reduced vitamin D production (eg, chronic renal disease); as the population ages, prevalence of chronic disease will rise
Increased medication use11Anticonvulsants, glucocorticoids, HIV medications, and some antirejection drugs reduce levels of vitamin D
Limited dietary choices12Fatty fish and fish oils are the only ample food source, and are becoming increasingly unavailable
Reliance on food fortification13Food sources are inadequate; in Canada, cow and soy milks and margarines are fortified
Migration of populations5Rapid migration of people with pigmented skin toward polar areas can reduce skin synthesis as much as 99%
Traditional clothing14All clothing impairs synthesis; Muslim women wearing traditional clothing have a 2.3 odds ratio of developing osteoporosis
Obesity15A 2006 survey found that two-thirds of the US population was overweight or obese; vitamin D is sequestered in body fat, and levels are inversely related to BMI
Reduced exercise opportunities16Vehicle prioritization, poor urban planning, and poor air quality force many to exercise indoors
Skin pigmentation4Melanin is a very efficient blocker of UVB radiation
Season5Very little vitamin D synthesis can occur from sun exposure in northern latitudes in winter months
Sex17,18Women are at increased risk of deficiency because of reduced peak bone mass, increased pregnancy demands, and traditional attire in some areas
Metabolic demand19Rapid skeletal growth in utero and in early infancy increases demand for calcium and vitamin D; breast milk is a poor source
Malabsorption5Vitamin D is fat-soluble; therefore, those with fat malabsorption syndromes such as Crohn disease or celiac disease are at risk
  • BMI—body mass index, SPF—skin protection factor.