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Lately, when I perform physical exams, I’ve been including Vitamin D levels with the routine lab tests. Very frequently, these levels come back low. Is this important? What does it mean to have a low Vitamin D level, and what impact does that have on our health?
Vitamin D is actually a group of five fat-soluble vitamins known as D1, D2, D3, D4, and D5. Of these, D2 and D3 are the most important to us. Known as the sunshine vitamin, Vitamin D is synthesized in the body from sun exposure, and is also consumed in the diet from food and/or supplements. Vitamin D is well known for preventing rickets in children and osteomalacia (softening of the bones) in adults. Together with calcium, it protects adults from osteoporosis.
Some of us live in areas with very little sunshine, or restrict our sun exposure for health-related reasons. To make up for that, we can increase our intake of Vitamin D-rich foods, including some fish (salmon, mackerel, tuna, sardines), fortified milk and fortified orange juice, beef liver, and eggs. Vitamin D supplements are also readily available, and it is included in most multivitamins. Note that because Vitamin D is a fat-soluble vitamin (as are Vitamins A, E, and K) it is stored in the liver and fatty tissues, and does not need to be replaced every day. Because it is stored, however, it poses a greater risk for toxicity if too much is taken. Nevertheless, I generally recommend that adults take a Vitamin D supplement of 1,000 IU per day.
The beneficial effects of Vitamin D on health are not all clearly proven, but current studies indicate that:
•It is crucial for the absorption and metabolism of calcium and phosphorus, which have various functions, especially that of maintaining healthy bones.
•It plays an important role in immune system regulation. During months of little sunshine when our production of Vitamin D is low, there is a higher prevalence of flu and other viral infections. Many factors may be in play, and researchers are investigating further.
•Researchers have found a correlation between Vitamin D levels and memory function. It may play a role in helping us maintain our mental agility. Stay tuned!
•There may be a correlation between levels of Vitamin D and adolescent and abdominal body fat. This has opened the doors to more studies on using Vitamin D supplements to aid weight loss.
•Low levels of Vitamin D have been linked to more severe asthma attacks in children. Taking supplements has been linked to fewer and milder attacks.
•Various studies link low levels with some cancers, but supplements do not appear to help.
•Low blood levels of Vitamin D are associated with increased mortality in general. Vitamin D3 supplements appear to decrease all causes of mortality, especially in elderly women.
•Also under investigation is the theory that Vitamin D might have a protective effect against multiple sclerosis. Multiple sclerosis occurs at high rates in regions of the world with long periods of little sunlight, and thus far less Vitamin D production in the body.
However, too much of a good thing can be harmful! Vitamin D toxicity, also called hyper-vitaminosis D, is a potentially serious but treatable medical condition. Toxicity comes, not from too much sunlight, but from too many supplements. The body can generally handle up to 10,000 IU (International Units) per day, but sustaining that level of intake for several months may lead to toxic symptoms.
We are more likely to become toxic if we have certain underlying problems, such as hyperparathyroidism. Symptoms of Vitamin D toxicity include nausea, frequent urination, weight loss, poor appetite, constipation, weakness, irregular heart rhythm, kidney stones, headaches, dehydration, fatigue, irritability, and muscle weakness. Treatment includes stopping all supplements and restricting calcium intake in the diet.
I wish for all of us good health and plentiful Southern California sunshine!
Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.
Published: January 12, 2012 – Volume 10 – Issue 39