Risk factors for vitamin D deficiency
| RISK FACTOR | MECHANISM |
|---|---|
| Lack of sun exposure5 | Reduced skin synthesis |
| Latitude of residence6 | No skin synthesis November to March at 52° north (eg, Edmonton, Alta) |
| Sunscreen use7 | SPF of 15 blocks 99% of skin synthesis |
| Urbanization8 | Increasing time indoors and increased automobile use |
| Aging9 | 75% reduction in skin production by age 70; increased institutionalization as a greater percent of the population ages |
| Increased chronic disease prevalence10 | Reduced 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 use11 | Anticonvulsants, glucocorticoids, HIV medications, and some antirejection drugs reduce levels of vitamin D |
| Limited dietary choices12 | Fatty fish and fish oils are the only ample food source, and are becoming increasingly unavailable |
| Reliance on food fortification13 | Food sources are inadequate; in Canada, cow and soy milks and margarines are fortified |
| Migration of populations5 | Rapid migration of people with pigmented skin toward polar areas can reduce skin synthesis as much as 99% |
| Traditional clothing14 | All clothing impairs synthesis; Muslim women wearing traditional clothing have a 2.3 odds ratio of developing osteoporosis |
| Obesity15 | A 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 opportunities16 | Vehicle prioritization, poor urban planning, and poor air quality force many to exercise indoors |
| Skin pigmentation4 | Melanin is a very efficient blocker of UVB radiation |
| Season5 | Very little vitamin D synthesis can occur from sun exposure in northern latitudes in winter months |
| Sex17,18 | Women are at increased risk of deficiency because of reduced peak bone mass, increased pregnancy demands, and traditional attire in some areas |
| Metabolic demand19 | Rapid skeletal growth in utero and in early infancy increases demand for calcium and vitamin D; breast milk is a poor source |
| Malabsorption5 | Vitamin 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.