Groups at Risk of Vitamin D Inadequacy

Obtaining sufficient vitamin D from natural food sources alone can be difficult. For many people, consuming vitamin D-fortified foods and being exposed to sunlight are essential for maintaining a healthy vitamin D status. In some groups, dietary supplements might be required to meet the daily need for vitamin D.

Breastfed infants
Vitamin D requirements cannot be met by human milk alone, which provides only about 25 IU/L. A recent review of reports of nutritional rickets found that a majority of cases occurred among young, breastfed African Americans. The sun is a potential source of vitamin D, but AAP advises keeping infants out of direct sunlight and having them wear protective clothing and sunscreen. As noted earlier, AAP recommends that exclusively and partially breastfed infants be supplemented with 400 IU of vitamin D per day.

Older adults
Americans aged 50 and older are at increased risk of developing vitamin D insufficiency. As people age, skin cannot synthesize vitamin D as efficiently and the kidney is less able to convert vitamin D to its active hormone form. As many as half of older adults in the United States with hip fractures could have serum 25(OH)D levels <12 ng/mL (<30 nmol/L).

People with limited sun exposure
Homebound individuals, people living in northern latitudes (such as New England and Alaska), women who wear long robes and head coverings for religious reasons, and people with occupations that prevent sun exposure are unlikely to obtain adequate vitamin D from sunlight.

People with dark skin
Greater amounts of the pigment melanin result in darker skin and reduce the skin's ability to produce vitamin D from exposure to sunlight. Some studies suggest that older adults, especially women, with darker skin are at high risk of developing vitamin D insufficiency. However, one group with dark skin, African Americans, generally has lower levels of 25(OH)D yet develops fewer osteoporotic fractures than Caucasians (see section below on osteoporosis).

People with fat malabsorption
As a fat-soluble vitamin, vitamin D requires some dietary fat in the gut for absorption. Individuals who have a reduced ability to absorb dietary fat might require vitamin D supplements]. Fat malabsorption is associated with a variety of medical conditions including some forms of liver disease, cystic fibrosis, and Crohn's disease.

People who are obese or who have undergone gastric bypass surgery
Individuals with a BMI ≥30 typically have a low plasma concentration of 25(OH)D; this level decreases as obesity and body fat increase. Obesity does not affect skin's capacity to synthesize vitamin D, but greater amounts of subcutaneous fat sequester more of the vitamin and alter its release into the circulation. Even with orally administered vitamin D, BMI is inversely correlated with peak serum concentrations, probably because some vitamin D is sequestered in the larger pools of body fat. Obese individuals who have undergone gastric bypass surgery may become vitamin D deficient without a sufficient intake of this nutrient from food or supplements, since part of the upper small intestine where vitamin D is absorbed is bypassed.