This article, which contains potentially life-saving information, is a comprehensive discussion of the importance of the hormone commonly referred to as "vitamin D" in the maintenance of good health. The article discusses the link between vitamin D insufficiency and numerous chronic diseases including cancer, heart disease, diabetes and more. This article offers a perspective on one of the factors that may cause African-Americans to be more prone to these illnesses, and provides information on what you can do to protect and enhance your health.
A brief word about calcium before we move on to the important topic of vitamin D:
Calcium is one of the most important elements in the diet because it is a structural component of bones, teeth, and soft tissues and is essential in many of the body's metabolic processes. It accounts for 1 to 2 percent of adult body weight, 99 percent of which is stored in bones and teeth. On the cellular level, calcium is used to regulate the permeability and electrical properties of biological membranes (such as cell walls), which in turn control muscle and nerve functions, glandular secretions, and blood vessel dilation and contraction. Calcium is also essential for brain function and proper blood clotting. When calcium levels fall too low, nerve and muscle impairments can result. Skeletal muscles can spasm and the heart can beat abnormally—it can even cease functioning!
Among the many other benefits of calcium is its ability to help regulate body weight. The link between calcium deficiency and weight gain has to do with your body's response to a calcium deficit. When you're low on calcium, your body thinks you're starving and enters emergency mode, releasing parathyroid hormone from four glands in your neck. This hormone stimulates your bones to release calcium into your bloodstream. Your kidneys also deliver a dose of a hormone called calcitriol, a form of vitamin D, to increase your ability to absorb calcium. The trouble is that parathyroid hormone and calcitriol also stimulate the production of fat and inhibit its breakdown. As a result, your body stores fat and holds on to it stubbornly, even if you're on a low-calorie diet.
Another benefit is heart protection. Research shows if you're low on calcium, you're more likely to have high blood pressure. The reason for this is the calcitriol released from the kidney in response to a calcium shortage acts on the smooth muscle walls of your arteries, constricting them and elevating your blood pressure.
Now to the important matter of vitamin D:
It is vitamin D that stimulates the intestinal absorption of dietary calcium, including calcium obtained through supplementation. Without vitamin D, only 10 to 15% of dietary calcium is absorbed.
While the role of vitamin D in calcium absorption is widely known, recent research has made some exciting discoveries regarding the link between vitamin D deficiency and numerous diseases. In fact, current research has implicated vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer as well as heart disease, high blood pressure, stroke, hypertension, autoimmune diseases, diabetes, depression, inflammatory bowel disease, macular degeneration, chronic pain, rheumatoid arthritis, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, periodontal disease, and more.
Vitamin D modulates the neuromuscular and immune functions and reduces inflammation. Additionally, and of great importance, the active form of vitamin D (1,25-dihydroxyvitamin D) modulates the growth of cells. In fact, the prostate, breast, colon, and many other tissues in the body have a vitamin D receptor and convert circulating 25-hydroxyvitamin D into active 1,25-dihydroxyvitamin D (more on these 2 forms of vitamin D later). Claims that vitamin D may help reduce the risk of such a wide variety of diseases seem incredible until one realizes vitamin D is not a vitamin. Vitamin D is a hormone. A March 2008 article for the Alternative Medicine Review by Drs. John J. Cannell and Bruce W. Hollis states: "Vitamin D's final metabolic product is a potent, pleiotropic, repair and maintenance seco-steroid hormone that targets more than 2000 human genes in a wide variety of tissues, meaning it has as many mechanisms of action as genes it targets". Vitamin D's influence on key biological functions vital to one's health and well-being mandates that it no longer be ignored by the health care industry, or by individuals striving to achieve and maintain a greater state of health.
There are 2 types of vitamin D; vitamin D2 and vitamin D3. Vitamin D2 is manufactured by plants or fungus. Certain foods such as juices, milk, and cereals are fortified with vitamin D2. Vitamin D3, on the other hand, is formed when the body synthesizes sunlight on the skin's surface. Solar ultraviolet B radiation penetrates the skin and converts 7-dehydrocholesterol in the skin to pre-vitamin D3, which is rapidly converted to vitamin D3. The body has a built-in mechanism for maintaining the optimal amount of vitamin D3 obtained from sunlight. Any excess pre-vitamin D3 or vitamin D3 is destroyed by sunlight. As a result, excessive exposure to sunlight does not cause vitamin D intoxication. Vitamin D, whether it's D2 from dietary sources or D3 from the synthesis of sunlight, is then absorbed into the blood-stream and transported to the liver, where it is hydroxylated and becomes what's called 25-hydroxyvitamin D. This is the major circulating form of vitamin D, and is what should be checked to determine your vitamin D status. 25-hydroxyvitamin D is then carried to the kidney where it is modified to its active form which is called 1,25-dihydroxyvitamin D. It is this form of vitamin D that tells your intestine to absorb calcium from your diet more efficiently.
Vitamin D can be obtained from four sources: sunshine, food, nutritional supplements, and tanning beds (please note, if you choose to increase your vitamin D production through the use of a tanning bed, use a bed with an electronic rather than a magnetic ballast as magnetic ballasts emit potentially harmful electromagnetic radiation). Few foods contain adequate amounts of vitamin D to satisfy our needs for this important hormone. In fact, 90% of vitamin D intake comes from sunshine. Only 10% comes from food sources.
In order for your skin to produce vitamin D3, the sun's UVB rays must be unobstructed and must make direct contact with the skin. Skin covered in clothing does not allow penetration of UVB rays. Even in the sunniest areas, vitamin D deficiency is common when most of the skin is covered. In studies in Saudi Arabia, The United Arab Emirates, Turkey, India, and Lebanon, where people cover most of their skin for cultural and religious reasons, 30-50% of children and adults had 25-hydroxyvitamin D levels below 20 ng/mL (nanograms per milliliter), which is a severely deficient state. UVB rays do not penetrate transparent materials such as glass. So being inside of an enclosed building or automobile with the sun shining in does not enable your skin to produce vitamin D3. The angle of the sun is also a very important determinant in the potency of UVB rays. UVB radiation is most potent when the sun is at its highest point. People who work indoors during this time of day are more likely to be vitamin D deficient. In fact, studies have shown people who work outdoors routinely have significantly higher levels of vitamin D than those who work indoors. People who are overweight are also more prone to vitamin D deficiency because body fat absorbs and sequesters vitamin D, making it unavailable to the body. And while being overweight makes you more prone to vitamin D deficiency, vitamin D deficiency in turn may lead to more weight gain because the absence of vitamin D creates interference with a hormone called leptin, which signals to the brain that you are full and should stop eating. Also, as we age our skin has less 7-dehydrocholesterol, and therefore is less capable of producing vitamin D3. Air pollution, cloud cover, and the use of sunscreen are also important factors in determining the amount of vitamin D3 you receive from UVB radiation.
The problem of vitamin D deficiency in African-Americans and other dark-skinned people:
The fact that most of our vitamin D intake comes from direct skin contact with the sun's UVB rays brings us to a point of particular concern for African-Americans. Due to our skin pigmentation, our skin does not produce nearly the amount of vitamin D we require. In fact, on average, African-Americans require a sun exposure level that is six times that which is required on average by Caucasian Americans to produce the same amount of vitamin D. African-Americans and other dark-skinned people are born with a built-in sun screen in the form of the skin pigment melanin that blocks most of the sun's beneficial UVB rays. Vitamin D deficiency and insufficiency are wide-spread throughout the African-American community. According to a study published in the Archives of Internal Medicine, 97 percent of African-Americans have vitamin D levels that are too low for optimal health.
In addition to the inhibitive effect melanin has on the production of vitamin D3, geography plays a big role as well. The farther one lives from the equator, the less potent UVB rays are due to the angle of the sun. This generally reduces the amount of vitamin D3 produced in those living at higher latitudes. In fact, above about 35 degrees north latitude (roughly north of Atlanta), little or no vitamin D3 can be produced from the sun from November to February (incidentally, this is a major reason the "cold and flu season" in America coincides with the winter months). As a result, supplemental doses of vitamin D generally need to be increased during the winter. People living at higher latitudes are at increased risk for a number of diseases including Hodgkin's lymphoma as well as colon, pancreatic, prostate, ovarian, breast, and other cancers, and are more likely to die from these cancers as compared with people living at lower latitudes. Living at higher latitudes also increases the risk of type 1 diabetes, multiple sclerosis, and Crohn's disease. Living below 35 degrees latitude for the first ten years of life decreases the risk of multiple sclerosis by approximately 50%.
Health disparities:
Disparities in the incidence of vitamin D deficiency between African-Americans and Whites are substantial. The CDC reported the results of a study of women ages 15-49 throughout the United States that showed 42% of African-American women were vitamin D deficient compared to 4% of White women. Recent research shows the definition of vitamin D deficiency used for this study is outdated, and that a much higher level of vitamin D is necessary for optimal health than is currently generally recommended. As mentioned previously, it is estimated the rate of vitamin D insufficiency in African-Americans is as high as 97%.
Equally alarming are the disparities between Blacks and Whites in America in the rates of various diseases in which vitamin D deficiency has been implicated: Based on the most recent data available from the National Cancer Institute as of this writing (2003-2007), the incidence of prostate cancer in African-American men is 56% higher than in White men. The incidence of pancreatic cancer is 32% higher in Blacks than in Whites. And the incidence of colorectal cancer is 25% higher in Black Americans. A July 19, 2007 article by Dr. Michael F. Holick, M.D., Ph.D. published in the New England Journal of Medicine cited the following: "both prospective and retrospective epidemiologic studies indicate that levels of 25-hydroxyvitamin D below 20 ng per milliliter are associated with a 30 to 50% increased risk of incidence of colon, prostate and breast cancer along with higher mortality from these cancers". According to the CDC's 2009 National Vital Statistics Report, Blacks are 31% more likely to die from heart disease than are Whites. The American Heart Association reported in 2006 the death rate from high blood pressure was 197% higher for Blacks than for Whites. 2007-2009 national survey data for people aged 20 years or older diagnosed with diabetes show Blacks are 77% more likely to be diagnosed with diabetes as are Whites. The active form of vitamin D is known to synthesize a peptide capable of destroying M. tuberculosis. African-Americans are more prone to contracting tuberculosis than Whites, and tend to have a more aggressive form of the disease.
The solution:
The need to keep abreast of our vitamin D status and to optimize our vitamin D level is clear. Here's what you need to know to protect yourself from vitamin D deficiency:
The current U.S. RDA (recommended daily allowance) for vitamin D was recently changed from 400 IU (international units) to 600 IU for those from 1 to 70 years of age, and 800 IU for those over 70. As more scientific evidence emerges, many scientific and medical experts on vitamin D have concluded the currently recommended daily allowance is woefully inadequate. The RDA of 400 IU was adequate for the purpose for which it was developed decades ago, to reduce rickets. However, neither the old recommended daily intake level nor the recently revised recommended intake levels are sufficient to provide the much more important protection from the variety of illnesses recently associated with vitamin D deficiency.
Natural blood serum levels of 25- hydroxyvitamin vitamin D, those found in humans living in a sun-rich environment who receive plentiful amounts of direct skin exposure to the sun, are between 40-70 ng/mL. A number of studies confirm there are numerous health benefits to be derived from maintaining vitamin D levels within this range. Keep in mind the body has a built-in mechanism for maintaining the optimal amount of vitamin D3 obtained from sunlight, and that sunlight destroys any excess vitamin D3. The vitamin D levels in people who live in sun-rich environments and receive plentiful UVB exposure naturally normalize in this range. However, a study found of a group who at the end of summer had naturally achieved, on average, a level of 50 ng/mL through direct skin exposure to sunlight, 50% of them had dropped to less than 30 ng/mL by the end of winter. Clearly the levels obtained during the summer were not able to be maintained without an increased level of vitamin D intake during the winter.
According to the March 2008 article written for the Alternative Medicine Review by Drs. Cannell and Hollis, one should seek to maintain their 25- hydroxyvitamin D level in the 40-70 ng/mL range year-round. This level should be sought in all people – infants, children, pregnant women, lactating women, healthy young adults, and the elderly. However, in addition to the factors that determine the amount of vitamin D you receive naturally, there are a number of factors that impact your body's ability to synthesize and metabolize vitamin D. Therefore daily intake needs are highly individual, and the only way to determine your current vitamin D intake need is to have your current level tested, and then increase your daily intake until it is sufficient to maintain a level of 40-70 ng/mL. Generally a higher level of supplementation is going to be required during the winter.
There are blood tests to determine your level of both forms of vitamin D; 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The correct test your doctor needs to order is for 25-hydroxyvitamin D, which is the marker that is most strongly associated with overall health. My recommendation if you're in the U.S. is to use LabCorp. They use a standard testing methodology, and the test result requires no numerical adjustment. Simply have your doctor write a request for the 25-hydroxyvitamin D test on a sheet from his or her prescription pad, and take the request to your nearest location. LabCorp will draw a blood sample, and will send the result to your doctor's office. Initially, you'll probably want to be tested every three months, including one test at the end of summer and one at the end of winter.
For those requiring supplementation, the preferred type of vitamin D is D3. Vitamin D2 is approximately 30% as effective as vitamin D3 in maintaining serum 25-hydroxyvitamin D levels. Therefore up to three times as much vitamin D2 may be required to maintain sufficient levels.
According to Drs. Cannell and Hollis, treatment of vitamin D deficiency in otherwise healthy people with 2,000 – 7,000 IU of vitamin D3 per day should be sufficient for most people to maintain year-round levels between 40-70 ng/mL. For African-Americans and other dark-skinned people, the dosage level required is likely to be toward the higher end of this range or even a bit beyond. As a frame of reference, the blood serum level of 25-hydroxyvitamin D of the African-American publisher of this website, who supplements with 7,500 IU of vitamin D3 per day during the eight months of the year that allow for hour-and-a-half long bike rides a few times a week, and 10,000 IU of D3 per day during the indoor cycling season, ranges from about 50 ng/mL at the end of winter to 70 ng/mL at the end of summer. While vitamin D supplementation is not to be taken as a replacement to standard treatment, according to Drs. Cannell and Hollis, in those with serious illness associated with vitamin D deficiency, doses of vitamin D3 taken should be sufficient to maintain year-round levels of 55-70 ng/mL. If you are currently being treated with any medications, you should consult with a qualified health care provider before taking vitamin D supplements. Keep in mind the links between vitamin D deficiency and numerous diseases are recent discoveries. Your physician may not yet be aware of the most recent science on this topic, and may not be aware of the higher intake levels needed to provide important protection from the variety of illnesses recently associated with vitamin D deficiency.
While the body has a built-in mechanism that ensures you don't acquire vitamin D intoxication from overexposure to the sun, it is possible to accumulate a toxic amount of vitamin D through supplementation. This can result in hypercalcemia, a condition in which the calcium level in your blood is above normal. Your body stores calcium mainly in your bones, but calcium also resides in certain cells, particularly in your muscles and in your blood. Your body rids itself of any excess calcium through your urine, keeping a normal level of calcium in your blood. In chronic toxicity, first urine calcium, then blood serum calcium will begin to gradually increase when blood serum 25-hydroxyvitamin D levels exceed 150 ng/mL. Most patients with vitamin D toxicity fully recover by simply suspending their vitamin D supplementation. It should be noted that vitamin D toxicity is exceedingly rare and few practitioners ever see it. Drs. Cannell and Hollis report: "credible evidence of vitamin D toxicity in those chronically consuming 10,000 IU of supplemental cholecalciferol (vitamin D3) daily is absent in the literature. In fact, the literature contains few cases of cholecalciferol toxicity from supplemental use; virtually all of the reported cases of hypercalcemia are from faulty industrial production, labeling errors, dosing errors, and patients treated medically with pharmacological doses of ergocalciferol (vitamin D2)".
Ensure both adequate vitamin D levels and calcium intake:
As mentioned previously, vitamin D and calcium work synergistically. While vitamin D is one of the most prevalent "vitamin" deficiencies in America, calcium is the mineral most likely to be deficient in the average American diet. If you're not getting enough of this vitally important mineral from dietary sources, be sure to supplement your dietary intake.
Click here for the full report on this issue as well as other important health information from BlackHealthWeb.com.
Posted By: Patrick Delaney
Saturday, December 8th 2012 at 11:41PM
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