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Shera Raisen, M.D.
December 23, 2007
Do you know your Vitamin D level and why should you?
Vitamin-D, the pro-hormone vitamin, important in Healthy Bones and Preventing Infections and Cancer
What does Vitamin D do for us?
Researchers are calling attention to a vitamin-D deficiency epidemic.
It is now realized that: vitamin D has many important biological functions, people are not getting enough, and the recommended daily allowance is far too low!
Vitamin D is integral to building bones. The absorption of calcium, the reabsorption of calcium in urine, and the remodeling or mineralization of bones are all dependent on sufficient levels of Vitamin D. When bone density or mass is lost, it is called osteoporosis; as more bone is lost, the risk gets higher to sustain a hip fracture or vertebral fracture. Vitamin D may be more important even than calcium to prevent osteoporosis and thus bad problems like hip fractures. Vitamin D receptor sites are also found in muscles, and muscle pain or damage and balance problems can result from insufficient levels. Some patients with fibromyalgia get relief from increasing their vitamin D levels.
Vitamin D also functions in regulating immunity and inflammation, which can relate to such medical problems as cancer and infections.
Many research studies show evidence of vitamin D deficiency implicated in 16 types of cancers. One study implies that appropriate vitamin D supplementation would avert colon cancer, which claims 56,000 lives per year. Research at University of California analyzed the prior scientific papers from 1966 until 2004. They concluded that 1000 IU of D3 daily could decrease a person’s risk of colorectal cancer by 50%.
Some studies found that people who lived in geographical locations that received more sunshine, had lower rates of specific cancers, including breast cancers. The groups in the areas with least sunshine had higher rates of winter colds, flus and respiratory infections. After analyzing all the factors of people in the different geographical locations, it appeared that the Vitamin D levels were responsible for the functioning immune system in both preventing cancer and infections. More prospective (versus these retrospective studies) studies need to done to prove this hypothesis, but in the meantime experts are recommending testing and treating Vitamin D insufficiencies as the preliminary research is very strong.
Other diseases that may benefit from appropriate vitamin D function are osteoarthritis, cardiovascular disease, and metabolic syndrome.
Other similar research shows promise for prevention and maybe being part of treatment plans in cancers like prostate and breast.
Vitamin D is needed for healthy white blood cells; and vitamin D receptors are found on many immune cells that are needed for killing viruses and bacteria. Thus, winter darkness causes low vitamin D exposure and may contribute to “cold and flu” seasonal epidemics. A recent study showed that newborn babies whose mothers had insufficient Vitamin D levels were more frequently hospitalized or treated for serious respiratory infections.
What is the physiology of Vitamin D, a prohormone?
Believe it or not, sunlight, via its ultraviolet B rays, initiates the formation of active Vitamin D3 (cholecalciferol) in the skin—it converts the previtamin 7-dehydrocholesterol (DHC) to cholecalciferol (D3). This D3 as well as D2(ergocalciferol) from the diet end up in the liver, where they are hydroxylated to the active form of Vitamin D know as 25-hydroxyvitamin D. The parathyroid hormone (PTH) further hydroxylates it into 1,25-dihydroxyvitamin D, whose activity increased calcium being absorbed in the gut, increased calcium reabsorption in the kidney, and increases bone mineralization.
Calcitriol, the active form of vitamin D, can halt the growth and reproduction of cells and cause them to mature into their finished forms. Thus, cancer cells may be stopped in their rapid growth, while the cells in the immune system mature quickly and do their job.
It is also implied that vitamin D then can modulate immune function, because its special ability to turn cell functions on and off.
Vitamin D also stimulates the formation of cathelicidin, which has anti-bacterial effect.
Why are people deficient?
There are many reasons why there is widespread vitamin D deficiency. Reasons include the use of sunscreen, which blocks sunlight’s effect of catalyzing the formation of Vitamin D. People who live in area far from the equator (at higher latitudes) where there is less time and intensity of sun exposure are at risk of deficiency. Thus, people will receive less ultraviolet light exposure during winter months and with the avoidance of sun or use of sunscreen in the summer and spring, they develop vitamin D deficiency.
People with darker skin, such as Africans, have lower absorption of sunlight via the skin because of their melanin. The elderly have less 7-DHC in the skin. Many people avoiding foods that have added Vitamin D, such as some milks and cheeses. People who suffer from damaged gut lining, such as in inflammatory bowel disease, colitis, and celiac disease (gluten allergy), will not absorb the vitamin D.
All these reasons make vitamin D deficiency and the resulting problems of bone fractures, infections and even cancer, more common.
What levels are normal and what vitamins are recommended?
These important questions are being worked out.
Some labs use these guidelines:
Vitamin D-25 hydroxy 0 to 20 is deficient
20 to 30 is insufficient
30 to 40 is hypovitaminosis
40 to 100 is adequate
Some studies with elderly women who are at risk for fractures showed the best results (least number of fractures)when the women's D-25-OH levels were greater than 80 nmol/L.
Dr. Michael Holick, an authority on vitamin D, suggests a healthy serum level of 75 to 125 nmol/L.
People at risk for bone fractures, infection and cancer, should make sure their levels are more than 80 nmol/L. For bone health minerals such as calcium, magnesium and boron are important to take with the vitamin D.
Vitamin D is a fat-soluble vitamin and can thus be stored in the body in fat. Taking 2000 IU (international units) of D3 (not D2) per day is helpful to reach adequate blood levels, if a person is not very deficient. It is difficult to reach toxicity levels, unless 10,000 IU or more per day are taken over a long time. Because it is stored in the body, a person could also take a 5000 IU dose 3 x a week. Someone who is deficient, who has less than 50 nmol/L, could also take a weekly dose of 50,000 IU of D3 for 8 weeks, and follow levels. When 80 to 100 level is attained, they could take 1000 IU to 2000 IU daily and be followed. These amounts should be discussed with their physician and monitored.
Adequate sun exposure can also raise levels: about 15 minutes 3 times a week, between 11 am and 2 pm, to the extremities or back may be safe for most people. Patients should check with their doctors if this sun exposure is safe for their skin type and history.
Foods with vitamin D include fish, like cod, salmon and tuna; eggs; and fortified foods, like soy milk and breakfast cereals. However, the mercury is fish limits how much fish someone should have. So, get your vitamin D-25-OH level tested and start taking D3 1000 IU or more per day, and discuss and monitor with your physician.
Next installment: what are theories on what causes breast cancer; what’s the best ways to prevent, and what are best imaging studies.