A University of Colorado-Denver study published this week removed any doubt that sun avoidance in the past generation has led to skyrocketing vitamin D deficiency in American society.

“We found a marked increase in vitamin D deficiency over the past two decades,” UC researcher Dr. Adit Ginde told US News and World report this week. “Over three out of every four Americans now have vitamin D levels below what we believe is necessary for optimal health. African-Americans and Hispanics are at particularly high risk — nearly all have suboptimal levels.”

The study found that:

1) The number of people above 30 ng/ml in vitamin D blood levels — now considered the lowest definition of sufficiency — has decreased from 45 percent of the population two decades ago down to 23 percent — or a 49 percent decrease.

2) The greatest drops in vitamin D levels were seen among blacks, where levels of vitamin D levels of less than 10 nanograms per milliliter rose from 9 percent to 29 percent — a 322 percent increase. In other words, almost one-third of blacks in the United States are severely deficient in vitamin D.

3) Blacks with vitamin D levels of more than 30 nanograms per milliliter or higher dropped from 12 percent to 3 percent — meaning 97 percent of blacks in the United States are vitamin D deficient.

“These findings are alarming and remove all doubt that sun avoidance in the past 20 years is causing this problem,” Smart Tan Vice President Joseph Levy said. “Sun scare practitioners may find themselves in a position of liability now unless they change their ways.”

To read the US News story click here.

To read Scientific American’s coverage of this story click here.