Even when Summer arrives (finally!), Vitamin D is a hot topic. Search Medline, an online database of citations and abstracts from health and medical journals, and you'll find 35,854 documents related to this vitamin. So what is all the fuss? Well, vitamin D is both a hormone and a vitamin; it is fat-soluble and essential for maintaining normal calcium metabolism. But this is only the beginning. Vitamin D action has been established in the following tissues and organs: brain, nerves, immune cells, pancreas, breast, liver, intestine, kidney, prostate, parathyroid, fat, skin, and, of course, bone. There are many other potential health benefits of vitamin D: sufficient levels can prevent rickets, osteoporosis and osteomalacia, prevent certain cancers and regulate your immune system. When comparing children and young adults who have had the most and the least amount of sun exposure, those with the most had a 40% reduced risk of non- Hodgkin's lymphoma and a decreased risk of dying from malignant melanoma once it develops. People who are born and raised at higher latitudes are at increased risk of developing multiple sclerosis, Crohn's disease, type I diabetes, osteoarthritis and rheumatoid arthritis. These risks, however, are reduced significantly in people who take vitamin D supplements. Vitamin D deficiency has also been associated with hypertension and cardiovascular disease. Lastly, there is some, although limited, research suggesting a link between low levels of vitamin D and psychiatric conditions such as schizophrenia and depression.

Your body can produce it naturally year-round if you live in the tropics; in our temperate climate, however, this is not the case. Just 10 to 15 minutes of summer sun exposure three times per week is enough for fair- skinned people to maintain an adequate level of this important vitamin during the summer and fall. If you have dark skin, use sun block or avoid the summer sun, then your body may not be producing sufficient vitamin D year-round. When the ultraviolet-B (UVB) rays from the sun hits your skin, your body produces vitamin D. If you are an adult woman with light skin and you are wearing a bikini, exposure to the sun for 15 to 20 minutes will cause your skin to generate approximately 10,000 IU of vitamin D3. However, the darker your skin color the longer you need to stay in the sun in order to create vitamin D because darker skin pigment blocks the effects of the sun. Likewise sunscreen blocks at least 90% of your vitamin D production, so try putting your sunscreen on after you get in the sun. By the time it absorbs you will have produced your vitamin D. While there clearly are risks associated with frequent sunbathing, sensible sun exposure is likely to allow your body to produce adequate amounts of vitamin D while not putting you at great risk of skin cancer.

There are 3 ways to get vitamin D: from exposure to sunlight, dietary sources, or supplements. If you live in Portland (or anywhere in a temperate zone), even if it didn't rain much, between the months of November and March, the sun is at such an angle that we do not get enough UVB rays to produce sufficient vitamin D. Unfortunately, there aren't many foods that are rich in this vitamin, so just eating a healthy diet does not guarantee that you are getting the vitamin D you need. Fortified milk contains less than 100 IU of vitamin D per serving, egg yolks 20 IU, cooked tuna or sardines between 200 to 360 IU per serving, and wild salmon between 600 to 1000 IU per serving. Cod liver oil is a vitamin D powerhouse, clocking in at over 1300 IU per tablespoon. In the US, good quality vitamin D supplements are available over the counter. And they are inexpensive. New Seasons sells Carlson vitamin D3 (1000 IU), 100 capsules, for less than $6.

So how much do you need? The jury is still out on this one. According to the Institute of Medicine, the daily adequate intake (AI) for all people under the age of 50 is 200 IU daily, 400 IU between the ages of 50 and 70 and 600 IU for individuals over the age of 70. Some experts believe that the recommended daily allowance of vitamin D is too low. Way too low. Without adequate sun exposure, most people need between 800 to 1000 IU per day. There are certain medical conditions and circumstances in which you may need more or less. For brief periods of time, doses of up to 10,000 IU per day have been found to be safe, and some experts advocate for daily doses of 2,000 to 5,000 IU. Since this vitamin is fat soluble, it is possible to develop vitamin D toxicity. In order to maintain an adequate level of vitamin D, you could have your physician order a 25-hydroxy vitamin D level. This simple blood test is ideally performed after fasting for 8 to 12 hours. While the reference range is broad, in order to get the benefits of vitamin D it is best to maintain a level near 50ng/ml.

In sum, our bodies are loaded with vitamin D receptors and deficiency of this important vitamin has been linked with diseases ranging from breast, colon, prostate and other cancers, multiple sclerosis, and osteoporosis, to name a few. If you live in a temperate zone, as we do here in Portland, even if you get adequate, sensible sun exposure in the summer you are still at risk of being vitamin D deficient in the winter and early spring. There are some health conditions in which higher doses of vitamin D should be avoided, so it is best to discuss supplementation with your physician before getting started.

By Portland Health and Wellness