Will Smith, Kobe Bryant and the incumbent United States President Barack Obama may need more Vitamin D than fair-skinned men, according to the study conducted by Northwestern University Feinberg School of Medicine.

Vitamin D or cholecalciferol is obtained by exposure to bright sunlight. The human body has specialized cells or "receptors" that will activate their function upon receiving stimulants like the UVB rays with adequate intensity. Once these specialized cells received the rays, they are stimulated to produce Vitamin D.

African-American men who live in areas having insufficient sunlight are 3 ½ times more vulnerable to suffer from vitamin D deficiency than Caucasian men.

"This study shows that the current 'one-size fits all' recommendations for 600 International Units of Vitamin D do not work," stated Adam Murphy, MD, professor of Urology at Feinberg School of Medicine.

"Skin color and sunlight exposure need to be considered for recommended daily allowances of Vitamin D," he added.

Scientific Explanation

Researchers behind the study identified the melanin as the cause for such vulnerability. Dark-skinned men have more melanin, the dark pigment in the skin that blocks the essential UVB rays from penetration into the skin. Because of this, men of African-American descent are required to raise their sun exposure up to six times.

"It takes a dark-skinned male like myself 90 minutes three times a week to absorb enough sunlight to produce the recommended amount of Vitamin D compared to just 15 minutes three times a week for a Caucasian male," continued Murphy.

African-American black men living in Chicago are urged to take vitamin D supplements up to 2,500 IU to obtain its healthy level.

Lifestyle Factor

Adam Murphy presented his research at the American Association of Cancer Researchers Health Disparities Conference in Washington, DC. He collaborated with Rick Kittles, an associate-professor of medicine at the University of Illinois in Chicago, and they recommended varying vitamin D supplements should fit to the lifestyle of men living in several areas.

"All men living in the northern third of the country-from Northern California to Virginia-need to increase their vitamin D supplement. But some residents in other areas do not favor much the outdoors like those who live in California or Washington," Murphy said, hinting that amounts of vitamin D varies in every region.