top of page

Limited UV Exposure & Vitamin D


Civilization here on earth took off around 6,000 years ago. Where? Not in the arctic circle! Indeed, human societies tended to locate in warm regions when they enjoyed year round sunlight. Living outdoors for the most part is what we were designed to do.

Living indoors year round is unnatural. Over the last few years we're finding that when something is manmade, when it's artificial, we seem to get into trouble. So it goes with staying out of the sun. Let;s talk about those troubles , and then conclude with some practical ways that folks with XP can limit these woes.

Fun Facts:

Sunlight can be broken down into three components:

Infrared (60%)

Visible (37%)

UV (3%)

Ultraviolet light can be further sub-divided into UVA (320-400 nanometers) and UVB (290-320 nm). UVA burns skin more quickly. UVB penetrates further. UV light, which is invisible and makes up of only 3% of sunlight, is a two -edged sword. We know that it can cause DNA damage and bad burns, but it also sets a remarkable chemical reaction in motion.

When UVB strikes our skin, 7 dehydro-cholesterol is converted into cholecalciferol, a vitamin D precursor. This substance then travels from the blood vessels near the skin surface to the liver, where it is converted into calcidiol (25-hydroxy). This is our vitamin D depot, and it is usually what doctors measure to tell whether we have to little or too much in our system. Finally, calcidiol is converted by the kidneys into calcitriol (1,25-hydroxy vitamin D), the most potent form of the hormone (yes, vitamin D is really a hormone).

How much is made? Lots. 20 minutes in summer sun in a bathing suit

can give us 20,000 units. Lifeguards generate up to 60,000 units in a

day. Remarkably, when we've had our fill, even with ongoing sun

exposure, production stops. One does not get vitamin D poisoning from

spending too much time outside.

Now, compare that with dietary sources. Our typical best source: a

glass of fortified milk. That gives us 100 units. Think of it. Just

one minute in the summer sun gives us as much vitamin D as 10 glasses

of milk!

What is the RDA (recommended daily allowance)? 400 units at present,

but some are saying that for those who spend a lot of time inside, the

RDA should be much higher , over 1,000.

So, what happens if you don't drink ten glasses of milk per day and

spend most of your life inside? UVB, the wavelength that really makes

vitamin D, does't penetrate glass , we don't get much of a tan

inside. Vitamin D deficiency can thus result. Is that a problem?


In a word, yes! Big problems. Consider some recent findings

regarding cancer of the colon, prostate, breast, and ovarian cancer.

Death rate from colon cancer in Northern Ireland is 160 per million.

In Guatemala, it's 5. Rate in Florida is 50% less than New York.

Breast cancer in Northern Ireland occurs at 270 per million. In

Guatemala, it runs at 23 per million. Likewise, the rates of prostate

and ovarian cancer fall as one heads toward the equator.


Rarely mentioned facto id about hypertension: our blood pressure runs

lower in summer.

What about diabetes? Well, it's known that sun exposure lowers

blood sugar. Consider that 90% of obese persons are vitamin D


Many folks get the winter blues, referred to as seasonal affective

disorder (SAD). This may be related more to a lack of visible light

that low vitamin D levels. The lux is a unit of visible lights.

Indoor lighting typically runs 150 to 600 lux. The noonday sun puts

out 100,000 lux! Even an overcast winter day puts out 1,000. When

visible light enters the eye, it triggers the brain to produce

serotonin and suppress melatonin. The former leads to a feeling of

well-being, and the latter to better sleep. It's no surprise that

most of us develop "light hunger" by mid-winter.

Consider the effect of sunlight on some other conditions. Neonatal

jaundice is relieved by sun exposure. This was first noted in 1956 by

a nurse in Essex, England.

Auto-immune disorders get better in the sun. The rates of multiple

sclerosis, rheumatoid arthritis, and Crohn's disease are all lower

in Florida than New York.

Low levels of vitamin D are associated with hearing loss. Perhaps

this is why some folks with XP lose their hearing.

Bone diseases do better in the sun. Not just rickets, but also

osteoporosis and osteomalacia. (More hip fractures occur in winter).

More tooth decay occurs this time of year as well.

Our immune system is stronger in the sun. For years before TB drugs

were developed, doctors successfully treated patients with sun light /


Many skin diseases -- acne, eczema, psoriasis, all do much better

in summer. Wounds heal better in summer.

But what about melanoma? There are three kinds of skin cancer ,

and this is the bad one. Prolonged exposure to artificial light may

suppress immune system and increase risk of melanoma. This skin

cancer seldom occurs in outdoor workers. Why? Two reasons. Likely

because they gradually tan as the sun gets gradually more intense

early in the summer. And they generate a lot of vitamin D , which

has an anti-cancer effect.

While sunburn unquestionable bad news , increase chance of cancer

and scars, vitamin d production with gradual tanning is protective.

Parts of the world with the greatest use of chemical sunscreens have

seen the greatest increase in the incidence of melanoma! Punta Arenas

, a city in southern Chile that sits close to the ozone hole with

high UVB levels -- shows no increase in skin cancer.

Practical Suggestions

If you have XP or other photosensitivity disorder, don't

stop practicing UV avoidance. Without the repair enzymes, DNA damage

can occur. Don't guess. Use a meter when in a new environment.

Use full spectrum lighting indoors. These have a balance of

blue, red, and other visible wavelengths that make the light they

throw off closer to natural sunlight than regular household bulbs or

fluorescent. This may help one avoid SAD.

Limit sunscreen use. If you can't pronounce or spell the

ingredients, be cautious. Zinc oxide is hard to beat for safety and


Measure your vitamin D level every three months.

If you do not get any significant sun exposure at all, take

cod liver oil, about one teaspoon per 50 pounds body weight daily.

Take anti-oxidants. These reduce free radical damage, may

actually help prevent sunburn. The best ones may be beta carotene.

It's very safe (can't overdose on carrots). It's also a

sunscreen (it gets deposited in the skin). Others include vitamin C,

vitamin E, garlic, green tea, and dark berries.

(Dr Joseph Malak, summary of presentation at Camp Sundown 2006)

Featured Posts
Recent Posts
Search By Tags
Follow Us
  • Facebook Basic Square
  • Twitter Basic Square
  • Google+ Basic Square
bottom of page