Why vitamin D is important to our health and which type of vitamin D is more potent.
Vitamin D is known as the sunshine vitamin because we get much of our vitamin D from the sun. Over the last two decades, studies have found that the level of vitamin D has dropped dramatically in Americans; this is probably because we have been told to stay out of the sun or use sunscreen.
There is new enthusiasm with vitamin D studies showing that it does boost the immune system and fight off viral infections such as the flu and at the same time tempers the immune system from overworking, which can create more mucus and fluid in the lungs, causing further problems such as pneumonia. Michael Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine, said “What vitamin D really does is play a sentinel role.” What that means is that vitamin D is used by the immune system to fight infection and it also helps to control the immune response and limits inflammation. By "tempering" the immune system in this way, it keeps the immune system from literally overworking, which can actually lead to death and is suspected in many of the deaths in the 1918 flu pandemic.
Researchers from the Harvard Medical School did a study between 1988 and 1994 with 19,000 people aged 12 and older, with an average age of 39, and found a link between low levels of vitamin D and upper respiratory infections. Those with low blood levels of vitamin D were 55% more likely to get a cold, flu or an upper respiratory infection.
Vitamin D signals the intestines to absorb calcium. With low levels of vitamin D, the body will break down bones to get the calcium it needs. Without enough vitamin D, the body cannot absorb enough calcium to satisfy the body’s need for calcium, no matter how much calcium you consume in food or supplements. The proper use of calcium is needed for the functioning of the nervous system, bone growth and bone density. Increasing vitamin D can help prevent non-vertebra fractures and reduce the risk of osteoporosis.
A link has also been found between low levels of vitamin D and certain cancers. New studies have shown that vitamin D could be protective against colon, prostate, breast and other cancers. There is also evidence that vitamin D could play a role in the prevention and treatment of diabetes type I and type II, hypertension, glucose intolerance, multiple sclerosis, some autoimmune diseases, schizophrenia and other medical conditions. Two small studies have suggested that vitamin D3 supplements provided benefits in people with active tuberculosis. In 2007, an analysis of 18 different randomized studies found that vitamin D supplementation might even help people live longer.
Researchers at the University of Pennsylvania have found that vitamin D may slow the decline in the ability to breath in people with asthma and COPD. The researchers believe that by slowing this progressive decline, they can prevent or delay the irreversible decline in breathing that leaves many asthmatics even more vulnerable when they suffer an asthma attack.
Since there aren’t that many foods sufficiently rich in vitamin D, the sun is then our only source for getting vitamin D. We have been told to stay out of the sun or use sunscreen, and sunscreen does an effective job of blocking the vitamin D. During the fall and winter months, we don’t get much, if any, vitamin D from the sun, and most of us don’t even get 400 IU from our diet, since there just aren’t enough foods with vitamin D in them. To get just the minimal RDA required--400 IU per day--you would have to drink 1 quart of milk or eat 5 ounces of salmon or a 6-ounce can of tuna. Milk doesn’t have any vitamin D in it naturally; it is fortified with it in the US.
There are two types of vitamin D: one is D2 (ergocalciferol) and the other is D3 (cholecalciferol). Vitamin D3 is the more potent of the two. When you look at multivitamins or supplements, look for vitamin D3. The label should say D3 and or cholecalciferol. A good multivitamin should have 700-800 IU of D3. Vitamin D is a fat-soluble vitamin, when you take it you need to also have something with fat in it, a teaspoon of peanut butter for example.
Many are recommending that the amount of Vitamin D3 should be increased to 2,000 IU (50 mcg) in the fall and winter for healthy adults and 1,000 IU (25 mcg) for adolescents. The foods with the most vitamin D are cod liver oil, oily fish and fortified milk.
Vitamin D Protects Against Bone Fractures
A recent study concerning how calcium, dairy products or vitamin D was associated with bone fractures in adolescent girls aged 9-15 was published. The study had the mothers of 6,712 girls fill out a food frequency questionnaire every 12-24 months between 1996 and 2001 with a 7-year follow up period.
The conclusion of the study found that taking vitamin D was associated with lower stress fractures in adolescent girls who participated in high impact sports and activities. Calcium and dairy products were not found to protect against stress factors .
Even though calcium is important to our health, other studies have found that too much protein can actually flush the calcium out of our bones, making us more at risk for bone fractures. And milk and dairy products have a lot of protein in them. For more information, you can read Why You Should Get Calcium from Non-Dairy Foods.
Vitamin D Keeps the Flu Away
A new study reported in the American Journal Clinical Nutrition found that vitamin D3 can keep children from getting the flu. A randomized double-blind placebo-controlled study with 167 children found that those who took vitamin D got the flu less than those who didn’t take the vitamin D. 
Conclusion on Vitamin D
To sum this up, here is an impressive quote from the NIH report “A recent meta-analysis found that use of vitamin D supplements was associated with a reduction in overall mortality from any cause by a statistically significant 7%”.
Vitamin D3 sounds like a supplement worth taking. The studies linking low levels and illnesses make it worth taking. Getting at least 700 IU in the summer in a multivitamin should be fine and taking a total of 1,000 to 2,000 IU in the fall and winter is now recommended. In the spring and summer, get out in the sun. Even if it’s for a total of 30 minutes per day, sit in the sun with no sunscreen. Bare arms, lift your shirt up or take it off and get some needed vitamin D the natural way.
Drugs That Reduce Calcium and Vitamin D
Certain medications can affect the body’s ability to absorb calcium and vitamin D properly. If you take any medications and want to take a vitamin D supplement, you should ask your doctor if there are any problems.
Steroids: Corticosteroid medications such as prednisone can reduce calcium absorption and impair vitamin D metabolism.
The weight loss drug Orlistat (brand names Xenical® and alli™) and the cholesterol-lowering drug cholestyramine (brand names Questran®, LoCholest®, and Prevalite®) can reduce the absorption of vitamins D and other fat-soluble vitamins.
Both phenobarbital and phenytoin (brand name Dilantin®), used to prevent and control epileptic seizures, increase the hepatic metabolism of vitamin D to inactive compounds and reduce calcium absorption
Vitamin D supplements can interact with several medicines such as heart medications and drugs for high blood pressure. Make sure you talk to your doctor if you take any medication before taking a vitamin D supplement.
© 2009-2012 Sam Montana
 Vitamin D, Calcium, and Dairy Intakes and Stress Fractures Among Female Adolescents. Arch Pediatr Adolesc Med. Published online March 5, 2012. doi:10.1001/archpediatrics.2012.5
 Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.
Am J Clin Nutr May 2010 ajcn.29094
NIH Report on Vitamin D
Linus Pauling Institute paper on vitamin D
National Institute of Health (NIH) Office of Dietary Supplements