Good Afternoon, Merry Sunshine

NINAD JOG
July 30, 2010

I know ultraviolet rays are a part of direct sunlight, and I know they are blocked by glass windows and doors. But I wonder whether diffuse sunlight also contains UV rays.

We know we are surrounded by sunlight when we are in the shade on a sunny day or in a room with a window, even though sunlight may not be striking us directly. There should be no reason to suppose that diffuse sunlight contains visible light but blocks ultraviolet light.

Why does this matter, and why would I worry about it?

The skin's exposure to UV-B rays generates vitamin-D, a substance whose importance is thought to reach far beyond maintaining bone strength and preventing rickets.

Standing Tall

While I and just about all my friends and family members who have had our vitamin-D levels tested have been found to be deficient - or at least to have a non-optimal value of less than 50 - one family member is a notable exception. His vitamin-D level of 87 is head-and-shoulders above the levels of the rest of us, which are in their teens and twenties. (My level has risen from 22 to 50 after taking supplements for two years, but it’s nowhere close to 87.)

This family member has never taken any vitamin-D supplements, but he has a couple of advantages. He is fair-complexioned, so his skin produces vitamin-D at up to six times the rate of a dark complexioned person. He lives in a tropical part of India that receives abundant sunlight almost all year round.

But he doesn't sunbathe, since sunbathing isn't part of Indian culture. Nor is he exposed to much direct sunlight, since he works five days a week in an air-conditioned office building.

But what he does do - and the rest of us don't - is stay bare-chested at home on the weekends. He can do it since it is warm all year-round, and Indian culture does not require him to keep most of his body covered, like it forces women.

All the windows in his home are open at all times of the day and night, as is typical in India. What he gets in abundance on the weekends - and those of us living in the U.S. don't - is abundant diffuse sunlight unblocked by any glass windows or doors.

Given his high level of vitamin-D, you’d think he’s young, for young people's bodies are more efficient at producing it from sunlight than older people's bodies. But he's in his early seventies.

Following in the Footsteps

I do not know whether being bare-chested at home during the day is the key to this family member's high vitamin-D level. My hypothesis may be wrong, but I figured there would be no harm in trying it out.

So I've started doing the same at my home in the U.S. I switch off my air-conditioner during the day and keep the windows and the balcony door open. I can do it only for another couple of months before autumn sets in, stealing much of the ultraviolet light from sunlight and robbing my open-window apartment of its warmth.

I won't know how much of a contribution - if any - the diffuse sunlight will make in raising my vitamin-D level, since most of the rise will be due to the 15,000 International Units (I.U.) per day (i.e. 105,000 IU per week) of vitamin-D supplements that I take.

Rays of Hope

I've also started doing what this family member doesn’t do: sunbathe as much as I can. I walk or jog in my neighborhood in the late afternoon after returning home from work. I go bare-chested, without slathering any sunscreen for an hour on sunny days. I'll also try to go to the beach or the Mall in Washington DC - or any place where an un-muscular, skin-and-bones figure like me can expose his back and his chest to the sun with impunity without feeling embarrassed. Even sticks need a shtick.

I sunbathed regularly two summers ago, only to learn that my vitamin-D level plunged to 22 at summer’s end from 29 at its beginning. I don’t know why my level went down, and I didn’t speculate.

I may be tilting at windmills, but I’m determined to catch every ray of sunshine, no matter how diffuse it is. And as you mull over the matter, let me start doing what it takes to change my name. Not to Merry Sunshine, but to Don Quixote.