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By Sophie Knab
The Amherst Record, September 2005

The medical world continues giving mixed medical messages for us to try and sort out. This time they center around Vitamin D.
Vitamin D plays its most critical role in maintaining healthy bones in both young and old alike. Research also indicates that it can help protect against numerous cancers such as that of the prostate, colon, breast, ovary and bladder by maintaining a healthy immune system. The major controversy seems to lie in what is the best way to increase our Vitamin D intake.
There are two ways to get Vitamin D. The first is to ingest it in food. There are a few good, natural food sources of Vitamin D, but many of us count on foods fortified with Vitamin D: milk and breakfast cereal and lately certain brands of orange juice.
The second source of Vitamin D is through exposure to the sun. The liver manufactures a Vitamin D precursor (an advance representative, so to speak, also called a pre-vitamin) that migrates to the skin. With the help of the sun's untraviolet rays (UV), the pre-vitamin undergoes another change. The liver and kidneys alter it again to produce the active Vitamin D hormone that scientists feel has become an imporant player in today's health issues.
The controversy: Should we take in more Vitamin D? Should we increase our exposure to the sun? Both questions only lead to more questions.
No one can disagree that if a substance can possibly prevent certain types of cancers, the substance or behavior should be encouraged. Some physicians and scientists are saying that the RDA (Recommended Daily Allowance) should be raised from 400 IU (International Units) to 1000 IU. Some propose increasing the upper limit to 2000 IU for children and adults. Not so simple. Vitamin D is what is called a fat soluble vitamin and by its nature can be stored up in the body. If you take in too much, it can cause toxicity. But what is enough? What is too much? Eating foods high in Vitamin D or foods that have been fortified with Vitamin D is the best guarantee of obtaining correct amounts of the vitamin. One cup of fortified Vitamin D milk supplies 100 IU. This is one-fourth of the recommended daily intake for adults between the ages of 51 and 70. Three ounces of tuna packed in oil will give you 200 IU. One tablespoon of cod liver oil will give you approximately 1300 IU. So we can obtain Vitamin D from food.
But what if someone is a poor eater? What if someone has a disease or condition that impairs the production of the active Vitamin D? Should they be given supplements? If so, how much?
Vitamin D in excess is the most toxic vitamin, causing damage to the kidneys and to the heart and lungs where it can cause death. What is the right thing to do? The jury is still out debating the issues.
Another way of obtaining healthy quantities of Vitamin D is from exposure to the sun's ultraviolet rays. The new advice being given out is to "get more sun." Unlike Vitamin D supplements, the sun imposes no risk of Vitamin D toxicity. But increasing exposure to the sun flies in the face of campaigns by some health officials interested in preventing skin cancer. The critical question seems to be: what is the definition of "more sun?" The formula being handed out: Figure out how long it takes your skin to turn pink in the sun. Expose a quarter of your body (hands, arms and face or arms and legs) to the sun for one quarter of that time.
This sounds so unscientific! The other problem is that the amount of color in the person's skin, determined by a compound called melanin, influences how much Vitamin D you actually make.
Melanin is a brownish-black coloring found in the skin of some individuals. Melanin blocks UV rays. The darker a person's skin, the longer the individual has to be in the sun to form the necessary amount of Vitamin D. So what is the definition of "more sun" for a very dark-skinned individual? Moderately dark-skinned? Someone from Ireland with extremely fair skin? Who should get more sun? People who are house bound? Anyone who applies sunscreen before stepping outdoors such as the elderly or mothers or their babies and small children? (A sunscreen with an S.P.F. of 8 blocks 95% of the skin's ability to make Vitamin D.) Or should it be those individuals who are living in crowded city areas with high pollution rates? Ultraviolet exposure varies by season, so the other question to consider is when we should get more sun. During our northern winter, when we don't get out as much? The truth of the matter is that season, geographic latitude, time of day, cloud cover and smog all affect UV ray exposure and Vitamin D synthesis. Until some of these issues are carefully researched and questions more carefully answered, the general advice to get "more sun" is not helpful and can be misleading. The bottom line is to try and sift carefully through all the mixed messages and be sensible. Eat well to include all vitamins, including D, in your diet. Try to get a little bit of sun for five to 10 minutes a day a few times a week, and after that wear your sun screen.