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As we will learn later, fair skinned people produce more than those of darker complexions with higher melanin content. The angle and time under the sun is also determinant; equatorial inhabitants fare better with vitamin D production than do those living in higher latitudes. In man, the newly produced Vitamin D goes through some additional changes in the liver to produce calcidol and from there further metabolization to the bioactive calcitriol by the kidneys and immune system’s monocytes-macrophages. Calcitriol is responsible for calcium and phosphorus concentrations in our serum as well as healthy growth and remodeling of bone. This substance also lessens the chances of hypocalcemia (low serum calcium). On the immune side, calcitriol converted by the macrophage system acts as a cytokine (a sort of chemical immuno-messenger) to help modulate immune function against microbes. Having renal (kidney) disease or liver damage can greatly impair circulating activated Vitamin D. Experiments show that Vitamin D2 absorbs UV-B radiation in fungi, plants and invertebrates and acts as a natural sunscreen against what the damaging sun’s rays can cause on DNA and cells. Vitamin D2 is not as bioactive in humans as is D3 for several reasons outlined below. Much of what has been used to fortify cow’s milk and other food products, however, has been Vitamin D2 prior to 2006, things have changed recently. As our knowledge of Vitamin D grows and with the current research trends, the food and supplement industries are pushing to utilize better preparations for supplements and fortifying foods. Those preparations are in the form of Vitamin D3, as the lesser expensively produced D2 form falls by the wayside. Deficiency in Vitamin D results in Rickets (a bone mineral loss disease), osteomalacia (soft bone disease) and osteoporosis (demineralization and bone matrix loss seen as we age). Supplementing with higher doses of Vitamin D3 beyond what will keep you out of trouble with Rickets has added health and wellness benefits. Vitamin D3 will reduce inflammation, influence genes that regulate proliferation, differentiation and apoptosis (cell death) in cells, thus playing a major role in cancer prevention. There have been studies showing benefit not only in bone health, immune function and cancer prevention, but also delaying onset and prevention of dementia, multiple sclerosis and schizophrenia. In history, Vitamin D played a major roll, for example Dr. Adolf Windaus won the 1928 Nobel Prize in Chemistry for his work with Vitamin D. Dr. H. Steenbock discovered, in the 1920’s, that irradiated foods produced higher levels of Vitamin D and that fortifying foods in this way would reduce Rickets. By 1945 with Dr. Steenbocks work recognized and his patent near expiration, the fortifying of milk and some staple foods was common practice; Rickets was all but eradicated in America. Along with producing Vitamin D naturally ourselves with sun exposure, dietary intake is the other form of receiving this beneficial nutrient. Intake can be measured in terms of micrograms or International Units (IU), where one mcg of Vitamin D is equivalent to 40 IU. More often foods and supplements are labeled using IU. The National Academy of Sciences (now know as the National Academies) recommends 200IU for those under the age of 50 years and 400IU for those over 50-years and 600IU for those over 70-years of age. The typical American diet however, averages 100 IU/day, but this is not saying much, as the “typical” American diet is rather poor when considering the fast foods we generally eat and the processed foods we buy. Despite this fact, the combination of adequate dietary intake and sun exposure may allow us to reach these recommended levels without supplementation; however, longevity and nutritional medicine physicians and organizations recommend quite a higher daily dose for wellness and health. Dosages of up to 5000IU/day are recommended in certain instances. Generally, a range between 1000 IU to 2000 IU is the standard recommendation by the Linus Pauling Institute and other organizations with a focus on prevention and nutrition. Foods that contain higher doses of Vitamin D3 are the groups of fatty fish, eggs and lean meat. For example, a 3.5 oz piece of salmon will give you 360 IU, Tuna (3.5 oz) will give you 235 IU, and Catfish tops the carts with 425 IU per 3 oz. A whole egg gives 20 IU and 15cc (a tablespoon) of cod liver oil is worth 1360 IU of Vitamin D3. Fortified milk (historically containing D2) will give on average 98 IU per 8 oz glass. It should be noted that a person would have to consume ten glasses of Vitamin D fortified milk daily to get the minimum effective levels for wellness of Vitamin D in their diet. The only vegan source, the mushroom, will bestow about 141 IU per gram of un-irradiated, and 500 IU per 100 gram of UV-B irradiated fungi. We can practically and efficiently measure our body’s stores of Vitamin D in the clinical setting. Measuring serum levels of 25-OH-Vitamin D is by convention the best way to assess levels, as this metabolite has a longer (15-day) half-life than other forms and assays serum and tissue levels quite well. Levels of > 30 ng/ml are desirable while >200 ng/ml are nearing the toxic (hypercalcemia, hyperphosphatemia) range. Levels below 30 are considered too low for good health. While “normal” ranges vary considerably from one reference lab to another, the widely accepted normal range for 25-OH-Vitamin D is between 30.0 and 74.0 ng/ml (32ng/ml – 100ng/ml by Life Extension Foundation).A person's fat (obesity) content is linked with lower vitamin D levels, not that fat blocks UV-B rays from doing their thing, but rather adipose tissue can store Vitamin D and take it out of serum circulation. Children born to women with lower levels of Vitamin D during pregnancy, have been shown to be at higher risk for Multiple Sclerosis (MS) and psychiatric disorders (schizophrenia). Researchers are finding that low Vitamin D levels can cause a drop in hair follicle growth, increase risk for peripheral vascular disease, cancers (breast, colon, prostate, ...) and neurological disorders. Rheumatoid Arthritis (RA) and other immune disorders, juvenile Diabetes (DM), Parkinson’s and Alzheimer’s Disease have also been implicated as resulting from low Vitamin D levels. It should be noted that natural Vitamin D production affected by skin pigmentation, as dark skinned people don’t produce as much as lighter skinned people may be the reason African-American men have a significantly higher risk for prostate cancer than do Caucasian men in this country.Researchers have learned that women with low Vitamin D tend to have children with twice the risk for schizophrenia. Some studies have shown that vitamin D supplementation can lower the doses of anti-psychotropic medication and have witnessed a drop in frequency of symptoms of schizophrenia in those patients. It is estimated that forty (40%) percent of the US population has a known vitamin D deficiency. In our nursing home patient population, it has been shown that some eighty (80%) percent have a deficiency. Unfortunately, some seventy-six (76%) percent of pregnant mothers show levels of deficiency, and the repercussions on their offspring are worrisome as one example is noted above. Studies conducted on patients with dementia, Alzheimer’s Disease and Parkinson’s Disease have shown some promise with regards to Vitamin D. Apparently, it acts on HLA-DRB1 genes and reduces MS in susceptible individuals as well. An active metabolite of 25-OH-Vitamin D converted by immune system cells will bind to Vitamin D Receptors (VDR) located on Natural Killer Cells (NKC), enhance phagocytosis in macrophages, increase T- and B- Cell function, and increase cathelicidine, a natural antimicrobial peptide, yet another downstream metabolite of Vitamin D. Experimentally and in theory, this is what is understood as Vitamin D’s importance to our immune function. This goes way beyond Vitamin D for bone health. Higher doses of Vitamin D3 have been shown to aid in absorption of calcium in our diet allowing for better bone mineralization, it acts as a hormone promoting bone development and health and has even been shown to have analgesic (pain killing) effects with bone pain in arthritic individuals. What is Vitamin D’s link to the Flu? It has been noted that with lower endogenous production due to decreased sun exposure in winter, in theory, a drop in Vitamin D effects immune system function to the point that we are more susceptible to the Influenza virus and may be responsible for passing it along more effectively. There are other factors as well that may prove this theory incorrect. Yet, it is sound advice to increase Vitamin D intake (high dose) when exposed or infected with the flu as it does gear up our immune system. Scientists have found and published reports that doses of Vitamin D in the range of 1000 IU/d will reduce colon cancer risk by 50%, breast and ovarian cancer by 30% and as little as 400 IU/d has shown in at least one study to reduce pancreatic cancer by 43%. When correcting a long standing Vitamin D deficiency, one must be patient, as it can take months to right low levels with proper supplementation. Vitamin D has also been linked to lowering elevated blood pressure and cholesterol, as well as Peripheral Vascular Disease (PVD). VDRs in the renin system, which is integral in blood pressure control can regulate the ACE- Angiotensin II conversion process that affects blood pressure. Low Vitamin D can cause Non-Insulin Dependent Diabetes Mellitus patients to produce less insulin secretion from the pancreas. It should be noted that in the medical literature, all deaths (due to all causes) rise when Vitamin D levels are less than 18 ng/ml.How much sun exposure is necessary to achieve levels of Vitamin D3? Experiments range in levels depending on ethnic groups and level of sun exposure (altitude and latitude), but in general for whole body irradiation without sun blockers in a Caucasian person, a dose of UV-B likely to just about induce a sunburn, will yield a comparative dose equivalent to between 10,000 and 25,000 IU taken orally. To put it more simply and practically, a fair skinned man wearing shorts and a t-shirt in mid-day sun at the equator for 10-minutes can produce 10,000 IU of Vitamin D3. You cannot produce toxic doses of Vitamin D (hypervitaminosis) with sun exposure, as there is an equilibrium state that is reached in the skin. As you reach this equilibrium point, Vitamin D3 is degraded as quickly as it is produced, thus prohibiting overproduction and toxicity. Obviously, from a pedantic perspective, sun exposure trumps dietary supplements as an inexpensive and practical way of achieving levels in the health range, however, skin cancer and photo-aging issues arise. Studies observing surfers in Hawaii noted quite a variance in Vitamin D production, so there is a good bit of variability, with sun exposure, time of day, region, ethnicity and skin pigmentation, leaving oral supplementation a viable recourse. Vitamin D3 makes for better supplementation than D2, as D3 binds with greater affinity to the Vitamin D Binding Protein (VDBP) that is responsible for carrying Vitamin D in the blood stream without degradation. Having a higher level of circulating VDBP/D3 allows the metabolite of 25-OH-Vitamin D (inactive D3), specifically 1,25-OH-Vitamin D, which is the bioactive form to attach to Vitamin D Receptors (VDR) on cells and at the nucleus. When active forms of Vitamin D attach to these VDRs that is where the magic happens. It is necessary for VDBP to carry 25-OH-Vitamin D to the liver and other cells for enzymatic metabolization, otherwise it would be degraded in our blood stream. The ability of Vitamin D2’s inactive precursor to do this is much less than D3. Vitamin D3 also has a longer shelf-life and is more stable than Vitamin D2 when placed in tablet or capsule form as a supplement or in fortified foods. Since 2006 the supplementation and fortification industry is switching over to Vitamin D3 more exclusively in higher-end products, despite the fact that it costs more to produce. With regard to drug interactions, there are some medications that block or interfere with production, others that interfere with the vitamin’s ability to bind with VDRs and block metabolism in the liver. Steroids impair Vitamin D metabolism, Xenical (aka orlistat or alli, a diet pill) and cholestyramine (cholesterol lowering medication) reduce Vitamin D absorption in the gut. And with lower Vitamin D levels, this affects the way calcium and magnesium are absorbed by the gut. Phenobarbital and Dilantin (both seizure medications) reduce absorption and metabolize Vitamin D into less active compounds. Dr. Saleeby is a nutritionally minded physician that offer consultation on diet, weight loss, wellness and natural hormone therapy. For more information visit www.saleeby.netReferences http://www.healthcentral.com/schizophrenia/news-296046-98.html http://en.wikipedia.org/wiki/Vitamin_Dhttp://ods.od.nih.gov/factsheets/vitamind/ http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/ http://health.usnews.com/health-news/family-health/heart/articles/2008/06/23/time-in-the-sun-how-much-is-needed-for-vitamin-d.html http://www.ajcn.org/cgi/content/full/84/4/694 http://www.naturalnews.com/003069.html http://news.discovery.com/human/vitamin-d-schizophrenia.html © 2010 |
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by JP Saleeby, MD
Vitamin D is a group of fat soluble secosteroids of which there are five known forms. Vitamin D1 through D5 are their designations as they were the 4th group of "vitamins" discovered and named; hence the "D", fourth letter in the alphabet designation. Vitamin D is not exactly a vitamin in the strictest sense, since humans do produce them endogenously. By definition a vitamin is a substance necessary for survival of an organism that is required to be consumed or ingested. Non-the-less, Vitamin D is a constituent nutrient where deficiencies lead to illness and disease, and supplementation is known to reduce illness, extend and enhance quality of life.