Just when you thought it was safe to go out in the sun (replete of course in head to toe SPF 30, hat and sunglasses), one vocal group is warning that these very sun protective actions may in fact lead to more cases of cancer than the skin cancer we work so hard to avoid.

Want to see a group of dermatologists get hot and bothered? Just mention the latest news to hit the Associated Press wire that suggests we toss our sunscreen and soak up enough solar Vitamin D to produce adequate levels of what some are now considering an anti-cancer Vitamin and ultimately reduce our risk of developing cancer. What's truth, what's hype, and what's realistic sun safety? Just keep reading.

Your RAYBC's of Vitamin D

Vitamin D is a relatively meaningless term. Cholecalciferol, also known as Vitamin D3 is the initial form of the vitamin our bodies ultimately utilize to properly absorb calcium and maintain appropriate levels of this vital mineral.

Our bodies can manufacture Vitamin D3. Ultraviolet B rays from the sun trigger our skin to produce cholecalciferol. It is estimated our skin makes approximately 20,000 IU during a 15 minute exposure to the sun.

Why simply implicate your bottle of sunscreen? While an SPF of 8 or higher fully eliminates Vitamin D3 production within the treated area, there are plenty of other reasons the skin doesn't make adequate Vitamin D. What are these individuals to do if they subscribe to the theory that Vitamin D has cancer-fighting properties?

If you live on the Northeast seaboard don't count on getting an adequate concentration of sunshine from November through February. And it's not just the geography. The time of day and season also factor in.

Cloudy day? Expect at least a 50% reduction of necessary UV rays essential to form Vitamin D.

Count on a 50% reduction in Vitamin D when it's smoggy. Shade accounts for a 60% reduction and glass windows eliminate it altogether.

Sounds like 3/4 of the nation needs to relocate to Florida rather than practice unprotected sun worshipping!

Then there are the biological causes of reduced Vitamin D production.

From a simple summer tan to individuals of color, increased melanin content will reduce the amount of UVB that can reach the skin and trigger Vitamin D3 production.

Diabetics can have lowered Calcitriol levels if their kidneys are unable to complete the final conversion of Vitamin D into this active molecule.

Old age reduces the skin's ability to manufacture Vitamin D3 from UV light exposure.

Supplemental Sources

Vitamin D3 also comes from certain natural foods including some fish (cod liver oil, salmon, mackerel, tuna and sardines), Vitamin D fortified milk, eggs, liver and can also be found in multivitamins and supplements.

Where does the National Institutes of Health (NIH) weigh in? Currently the RDA (recommended daily allowance) of Vitamin D (cholecalciferol) is 400 IU per day (also referred to as 0.025 micrograms) for a healthy adult. The older one becomes, skin becomes less capable of manufacturing Vitamin D3 and supplementation needs rise.

To dispute much of the pro-sun argument: While it is true according to the NIH that more than 50% of younger and older women are not consuming recommended amounts of Vitamin D, it is not difficult to find in food sources and supplementation. Milk contains Vitamin D fortification. So do most calcium supplements. Orange juice and even bread are being fortified with this vitamin.

Here's some information on Select Food Sources of Vitamin D from the NIH. The RDA is estimated for a healthy adult.

Cod Liver Oil, 1 Tbsp contains 1360 IU or 340% RDA

Salmon, cooked, 3 1/2 oz contains 360 IU or 90% RDA

Mackerel, cooked, 3 1/2 oz contains 345 IU or 90% RDA

Sardines, canned in oil, 1 3/4 oz contains 250 IU or 70% RDA

Tuna fish, canned in oil, 3 oz contains 200 IU or 50% RDA

Milk, nonfat, Vitamin D fortified, 1 cup contains 98 IU or 25% RDA

Margerine, fortified, 1 Tbsp contains 60 IU or 15% RDA

Fortified cereals, 3/4-1 cup contain 40 IU or 10% RDA

Egg, 1 whole (Vit D is in yolk) contains 20 IU or 6% RDA

Liver, Beef, cooked 3 1/2 oz contains 15 IU or 4% RDA

Swiss Cheese, 1 oz contains 12 IU or 4% RDA

I took a look at many multivitamins and supplements on the market. Here's what I found: Just because the label claims it's a Vitamin D supplement does not guarantee you are receiving Vitamin D3 which is the most active form of Vitamin D supplement and the ideal choice. Another "Vitamin D" in sheep's clothing known as ergocalcitriol aka Vitamin D2 (derived from irradiating fungus) may be a substitute in that multivitamin listing Vitamin D on the list of ingredients. Look lower on the label for the "real" vitamin names. You should see either Vitamin D3 or Cholecalcitrol to know you've picked up the real deal.

Cod Liver Oil as an option? The NIH states a tablespoon should contain 1360 IU or 340% of the RDA. I have to admit to recoiling in horror at the mere thought of having to consume a tablespoon of the stuff. What I found label reading is that many brands contained only small amounts of Vitamin D3. Gagging it down only to find the brand truly didn't contain what it was hoped to would be only that much more defeating. So, word to the wise: read the label to check out Vitamin D3 level (cholecalciferol) and consider taking it in a more friendly gel capsule form.

However this vitamin is obtained by the body, it must first be converted through a 2-step process before it is able to be utilized by the body.

Step One involves cholecalciferol being transformed into Calcidiol, (25 di-hydroxy-vitamin D) within the liver.

From there, the kidneys convert Calcidiol into Calcitriol (1,25 dihydroxy-vitamin D).

Calcitriol of course helps with absorption of calcium, necessary for cellular function and bone mineralization. Abnormally low calcium levels can lead to issues with nerve conductivity (numbness, tingling, depression, irritability, personality changes), muscle contraction (muscle cramps, tetany), heart function (heart failure, arrhythmias, low blood pressure), rickets in children and osteomalacia (thinning of the bones) in adults.

The Controversy

Some researchers are pointing to studies that suggest Vitamin D plays a significant role in the prevention and possibly treatment of certain cancers including those of the breast, colon and prostate. They claim that rising rates of cancer are due in part to sun prevention habits that lower the production and availability of cancer-fighting Vitamin D.

So according to the AP article, some of these researchers argue it's OK to ditch the sunscreen and soak up some sun.

To be fair, they aren't proposing full time sun worshipping, but rather recommend 15 minutes of unprotected sun exposure daily. But do we really want to abandon the very sun protection that is meant to prevent the more than 1 million new cases of skin cancer diagnosed each year and the 7,700+ skin cancer related deaths? And do we really need sunshine to provide us adequate Vitamin D in the first place?

Granted, research over the past few years and epidemiologic studies have certainly been thought provoking. It's possible that Vitamin D may indeed play a protective role in the prevention of cancer, and may even possibly improve chemotherapy survival. Where we differ is both how much Vitamin D is enough and how can we safely achieve it?

I'm certainly open to the concept that Vitamin D has a potential anti-cancer role, I'm even willing to accept the notion that perhaps the RDA may be on the low end and this could be scientifically evaluated by validated double-blind research to determine exactly how much (if any) additional Vitamin D should be bioavailable for cancer prevention.

What I find completely unacceptable is sending out a confusing and potentially misleading message, reversing twenty years of sun safety education based upon arguments easily solved by simply popping a pill.

Currently there is no agreement on exactly how much Vitamin D we should take to achieve this anti-cancer function (if indeed it exists). Arguments exist for ranges as low as the current RDA of 400 IU to as high as 4000 IU per day. For now, I urge caution not to take excessive amounts of Vitamin D which could be toxic. Limit your intake to 800IU/day which includes food and supplementation. If you are concerned about being Vitamin D deficient, your doctor can diagnose this easily with a simple blood test.

Audrey Kunin, M.D.

(Any topic discussed in this article is not intended as medical advice. If you have a medical concern, please check with your doctor.)

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