Does race affect a person’s Vitamin D level? The findings of a new study published in Arthritis & Rheumatism not only suggest that it does, but that low levels of Vitamin D make African Americans more sensitive to pain.
Researchers at the University of Florida and the University of Alabama at Birmingham say blacks have a greater chance of being vitamin D deficient than whites – which may lead to a greater degree of knee pain from osteoarthritis (OA). The National Arthritis Data Workgroup estimates that 27 million Americans have osteoarthritis.
“People associate vitamin D with good bone health,” said lead author Toni Glover, a research nurse practitioner who specializes in the study of pain in older adults. “Yet, not everyone is aware of what factors decrease vitamin D and how low levels could contribute to health issues, including chronic pain.”
Nearly a hundred black and white patients with symptomatic knee OA were involved in the study. They were 75% female and had an average age of 56 years.
Participants completed questionnaires on their symptoms, and were tested on their sensitivity to heat and mechanical pain. Mechanical pain was measured by the patients’ response to pressure in the knee and forearm. Patients were asked when the sensation “first becomes painful” and when they were “no longer feel able to tolerate the pain.”
Researchers found that despite exposure to a sunny southern climate, most of the black patients had vitamin D levels lower than white subjects. The average vitamin D level for blacks was 19.9 ng/mL, significantly lower than white patients who averaged 28.2 ng/mL.
Clinical practice guidelines state that vitamin D levels less than 20 ng/mL represent deficiency and levels between 21 and 29 ng/mL represent insufficiency.
Blacks in the study also reported greater knee osteoarthritis pain, and those with lower vitamin D levels displayed greater sensitivity to heat and mechanical pain.
“Our data demonstrate that differences in experimental pain sensitivity between the two races are mediated at least in part by variations in vitamin D levels,” said Glover. “It may be warranted that older black Americans with chronic widespread pain be screened for vitamin D deficiency to reduce disparities in pain.”
Most vitamin D comes from exposure to the sun, with some research suggesting that a deficiency of this vitamin may be due to more indoor activities, increased sunscreen use, and the need for longer sun exposure for those with dark skin pigmentation.
During the last decade, medical evidence has suggested the importance of vitamin D, not only as a vitamin that aids in calcium absorption, but also as a powerful hormone with numerous functions throughout the body.
Some studies indicate that decreased vitamin D levels can reduce immunity and may contribute to
diseases such as cancer and diabetes.
But the evidence supporting the benefits of vitamin D is far from conclusive.
A recent study by Dutch researchers at Leiden University Medical Center in the Netherlands found that individuals in families with long life spans tend to have low levels of vitamin D.