There have been concerns about the vitamin D status in the United States because of increasing reports of deficiencies, with an estimated 10 million Americans over the age of 50 diagnosed with osteoporosis.
Vitamin D is the only vitamin that also acts as a hormone. As a hormone, it regulates the calcium and phosphorus levels in the blood by promoting their absorption from the intestines, and by promoting re-absorption of calcium in the kidneys, which enables normal mineralization of bone and also helps to maintain muscle strength. Vitamin D also affects the immune system by promoting anti-tumor activity and immunomodulatory functions.
There is a high prevalence of vitamin D deficiency in the chronic kidney disease population. Diseased kidneys can’t remove excess phosphorous found in foods, as normal kidneys do. As phosphorous builds up, calcium in the blood drops. Four small glands in the neck, called parathyroid glands, then become too active, and too much calcium is removed from the bones. This causes them to weaken and possibly fracture. When parathyroid hormone, as well as blood levels of phosphorous and calcium, build up to excess, the risk of bone fractures, disability and death increase.
Vitamin D deficiency most commonly occurs as a result of inadequate sunlight exposure. Almost no one consumes enough vitamin D from foods to prevent a deficiency when exposure to sunlight is inadequate. However, there are concerns about adequate sunlight exposure and the fear of certain skin cancers, like melanoma. In addition, liver and kidney disorders also may lead to vitamin D deficiency.
Without enough vitamin D, muscle and bone weakness and pain occur. Infants may develop rickets and adults may develop osteomalacia or osteoporosis. The Vitamin D Council stated that vitamin D deficiency also could cause stroke, muscle weakness, muscle wasting and birth defects. Several studies have suggested that vitamin D deficiency contributes to cardiovascular disease, cancer and death.
Blood tests to measure vitamin D can confirm a deficiency, but X-rays also may be needed. The diagnosis of rickets or osteomalacia is based on symptoms, the characteristic appearance of bones on X-rays, and a low level of vitamin D in the blood.
A study published in the Journal of the American Society of Nephrology, links treatment with activated vitamin D to a 20 percent reduction in the risk of either death or dialysis in patients with chronic kidney disease. Appropriate use of active forms of vitamin D may improve the outcomes of patients with chronic kidney disease. If you have been diagnosed with chronic kidney disease, talk to your physician or nephrologist and discuss the options of vitamin D therapy to find out if it is right for you.
In order to get the proper amount of vitamin D your body requires, you need to be able to find a healthy balance of sunlight, while wearing sunscreen and keeping exposure to 20 minutes at a time to reduce the risk of skin cancer. Some of the natural sources of vitamin D include fish liver oils, fatty fish species, eggs, cooked beef liver and UV-irradiated mushrooms. Most people will not get enough vitamin D from sunlight or natural sources, and they may need to take vitamin D supplement.
Nephrologist Dr. Mohammad J. Shafi is board-certified in internal medicine and a fellow of the American College of Physicians.