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Wellness

Are you getting enough Vitamin D? Sunlight through glass doesn't count

You can't get adequate UVB exposure sitting indoors or in a car.

Are you getting enough Vitamin D? Sunlight through glass doesn't count

(Photo: iStock/recep-bg)

Sunlight doesn’t actually “provide” you with Vitamin D. Rather, your body produces Vitamin D when skin is exposed to the sun’s ultraviolet rays, which trigger Vitamin D synthesis.

The liver and kidneys convert this biologically inert form of Vitamin D into biologically active forms the body can use to promote calcium absorption and bone health.

But sunlight consists of both ultraviolet A or UVA, which penetrates deep within the skin layers and can cause premature ageing; and ultraviolet B or UVB, which causes the redness of sunburn.

It’s the UVB rays that trigger the synthesis of Vitamin D.

Many people can derive the Vitamin D that their bodies need through direct exposure to sunlight during the summer months.

As little as 10 minutes a day of sun exposure is typically adequate.

READ: Vitamin D and fish oils are ineffective for preventing cancer and heart disease

And you can’t get adequate UVB exposure sitting indoors or in a car. Virtually all commercial and automobile glass blocks UVB rays.

As a result, you will not be able to increase your Vitamin D levels by sitting in front of a sunny window, though much of the UVA radiation will penetrate the glass and may be harmful.

Those concerned about low Vitamin D levels can get more of the vitamin through foods.

The best dietary source for Vitamin D is old-fashioned cod liver oil.

Other dietary sources include swordfish and salmon and, to a lesser extent, fortified milk, orange juice and yogurt, as well as sardines canned in oil, egg yolks and fortified cereals.

Dietary supplements are also available.

By Roni Caryn Rabin © The New York Times

This article originally appeared in The New York Times.

https://www.nytimes.com/2019/02/08/well/live/does-sunlight-through-glass-provide-vitamin-d.html

Source: New York Times/yy

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