Older adults with deficiencies in vitamin D experience more rapid cognitive decline over time than those with adequate vitamin D levels, according to a study recently published online by JAMA Neurology.

“There were some people in the study who had low vitamin D who didn’t decline at all and some people with adequate vitamin D who declined quickly,” said Joshua Miller, professor and chairman of the Department of Nutritional Sciences at Rutgers University. “But on average, people with low vitamin D declined two to three times as fast as those with adequate vitamin D.”

The researchers said that their findings amplify the importance of identifying vitamin D insufficiency among older adults, particularly high-risk groups such as African-Americans and Hispanics, who are less able to absorb the nutrient from its most plentiful source: sunshine. Among those groups and other darker-skinned individuals, low vitamin D should be considered a risk factor for dementia, they said.

Another major source of vitamin D is dairy consumption, according to the researchers. The intake of dairy products is especially low among minority groups, however, with only 6.5 percent of African-Americans and 11 percent of Mexican-Americans nationwide consuming the recommended three daily servings of dairy products, they said.