Vitamin D: is it the missing link in (bone) health?
Most women past the age of menopause have probably been offered one of several drugs to treat or prevent osteoporosis. These drugs work primarily by inhibiting hormones like parathyroid, although in most cases these hormones are at healthy levels and are not what causes bone loss. The drugs may well lead to stronger bones, but toxicity and side effects are a real concern.
All of us know about the importance of calcium for bone growth in children and healthy bones in adults. However taking calcium alone has not been shown to help reduce bone loss and osteoporosis. One reason is that the body needs vitamin D to absorb calcium and deposit it in bones.
A recent study showed that taking 800 to 900 IU of vitamin D in addition to 1,200-1,300 mg of calcium resulted in increased bone density in both younger and older postmenopausal women. The study also revealed that vitamin D deficiency was widespread among aging individuals. Ensuring adequate intake of vitamin D and calcium would seem to be a reasonable first step in manag ing osteoporosis before even considering drugs that cause undesirable hormone disruption (J Women’s Health (Larchmnt) 2003 Mar; 12:2: 151-6).
Unlike other vitamins, our bodies can make Vitamin D. The skin has enzymes that, when exposed to the ultraviolet rays of the sun, convert cholesterol into Vitamin D. We also obtain some Vitamin D from food, but since the amount we get from the sun can vary a great deal, it is a challenge to determine exactly how much Vitamin D we need from our food or supplements.
The US recommended daily allowance (RDA) is 400 international units (10mcg) daily from infancy to adulthood, and it was long thought that intakes exceeding 2,000 IU daily posed a risk of toxicity. However, expert opinion is shifting on this point since it has become apparent that the body can make many times more Vitamin D from even brief exposure to the sun.
Deficiency of Vitamin D is probably becoming more common in part because of widespread use of sunblocks that interfere with the skin’s ability to synthesize this vitamin. Large doses of Vitamin A, while beneficial in certain cases, can also induce a deficiency of Vitamin D if the levels of the two vitamins are not monitored and maintained in proper balance.
Studies have also shown that Vitamin D plays a central role in regulating the immune system. People with low blood levels of Vitamin D have been shown to have a higher occurrence of numerous cancers, including prostate, breast, colon, and others. The rate of autoimmune disease is higher in those who are deficient in this important vitamin.
Regular but sensible exposure to the sun may be the best way to ensure adequate stores of Vitamin D. Individuals at risk for osteoporosis, those who take Vitamin A supplements, or those with immune system disorders should ask their healthcare professional to order a simple test called 25-hydroxy-vitamin D to help determine their level of this important vitamin.
