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 I'm starting to see studies questioning whether some of the beneficial health effects that many attribute to vitamin D may actually be due to sunlight. In the first study, researchers said that sunlight also has low levels of "blue light" which energizes T cells. T cells are a type of white blood cell, are part of the immune system, and help protect the body from infection and cellular abnormalities (cancer). So the blue light in sunlight had a positive effect on the T cells.

The second study examined whether it was low levels of vitamin D that is linked to multiple sclerosis (which is the widely accepted medical view) or was it low exposure to sunlight? They found that vitamin D is not associated with multiple sclerosis risk in blacks or Hispanics (but is in whites). But sun exposure is protective in all three racial/ethnic groups (blacks, Hispanics, whites). Thus it was the sunlight that was important in protecting against multiple sclerosis rather than vitamin D. Bottom line: for various beneficial health reasons, go out in sunshine frequently (20 minutes a day is fine). Remember, sunlight is the "natural source" for vitamin D (the ultraviolet light hitting our bare skin allows us to make vitamin D).

From Dec. 2016 in Science Daily: Sunlight offers surprise benefit: It energizes infection fighting T cells

Sunlight allows us to make vitamin D, credited with healthier living, but a surprise research finding could reveal another powerful benefit of getting some sun. Georgetown University Medical Center researchers have found that sunlight, through a mechanism separate than vitamin D production, energizes T cells that play a central role in human immunity.

Their findings, published today in Scientific Reports, suggest how the skin, the body's largest organ, stays alert to the many microbes that can nest there. They specifically found that low levels of blue light, found in sun rays, makes T cells move faster -- marking the first reported human cell responding to sunlight by speeding its pace.

"T cells, whether they are helper or killer, need to move to do their work, which is to get to the site of an infection and orchestrate a response," Ahern says. "This study shows that sunlight directly activates key immune cells by increasing their movement."

"We know that blue light can reach the dermis, the second layer of the skin, and that those T cells can move throughout the body," he says. ...."We found that sunlight makes hydrogen peroxide in T cells, which makes the cells move. And we know that an immune response also uses hydrogen peroxide to make T cells move to the damage," Ahern says. "This all fits together." Ahern says there is much work to do to understand the impact of these findings, but he suggests that if blue light T cell activation has only beneficial responses, it might make sense to offer patients blue light therapy to boost their immunity.

From Medscape: Is It Time to Rethink Low Vitamin D as a Contributor to MS?

The idea that vitamin D deficiency may contribute to multiple sclerosis (MS) has been well established in the literature and has, for the most part, been etched into recent neurology dogma. Yet, research by Annette Langer-Gould, MD, PhD—a clinical assistant professor at the University of Southern California's Keck School of Medicine in Los Angeles—suggests that the association might not be that simple. ....As background, the vitamin D–multiple sclerosis hypothesis originated from the observation that the prevalence of MS increases with increasing distance from the Equator, as ultraviolet radiation (UVR) from the sun becomes less intense. But this is also where more white people live.

The main result of our study is that vitamin D is not associated with MS risk in blacks or Hispanics, regardless of genotype. In contrast, sun exposure is protective in all three racial/ethnic groups.

Another study finding a benefit of coffee consumption - this time linked to a lower rate of MS. Keep in mind that numerous studies have shown a strong association of higher sunlight exposure (especially in childhood), and living at lower latitudes (more sunlight exposure) with lower rates of multiple sclerosis. From Science Daily:

Can coffee reduce your risk of MS?

Drinking coffee may be associated with a lower risk of developing multiple sclerosis (MS), according to a study released today that will be presented at the American Academy of Neurology's 67th Annual Meeting in Washington, DC, April 18 to 25, 2015."Caffeine intake has been associated with a reduced risk of Parkinson's and Alzheimer's diseases, and our study shows that coffee intake may also protect against MS, supporting the idea that the drug may have protective effects for the brain," said study author Ellen Mowry, MD, MCR, with Johns Hopkins University School of Medicine in Baltimore and a member of the American Academy of Neurology.

For the study, researchers looked at a Swedish study of 1,629 people with MS and 2,807 healthy people, and a U.S. study of 1,159 people with MS and 1,172 healthy people. The studies characterized coffee consumption among persons with MS one and five years before MS symptoms began (as well as 10 years before MS symptoms began in the Swedish study) and compared it to coffee consumption of people who did not have MS at similar time periods. The study also accounted for other factors such as age, sex, smoking, body mass index, and sun exposure habits.

The Swedish study found that compared to people who drank at least six cups of coffee per day during the year before symptoms appeared, those who did not drink coffee had about a one and a half times increased risk of developing MS. Drinking large amounts of coffee five or 10 years before symptoms started was similarly protective.

In the US study, people who didn't drink coffee were also about one and a half times more likely to develop the disease than those who drank four or more cups of coffee per day in the year before symptoms started to develop the disease.