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这一篇里有很多有用的信息。由于篇幅较长，所以单开一线贴出。建议大家耐心读完全文。
AF
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The Miracle of Vitamin D (ZT)
By Krispin Sullivan, CN
NOTE: Be sure to read the Winter 2000 and Fall 2002 updates to this article, at the end of the original article.
Contents
The Miracle of Vitamin D In April of 2000 a clinical observation published in Archives of Internal Medicine caught my attention. Dr. Anu Prabhala and his colleagues reported on the treatment of five patients confined to wheelchairs with severe weakness and fatigue. Blood tests revealed that all suffered from severe vitamin D deficiency. The patients received 50,000 IU vitamin D per week and all became mobile within six weeks.1
Dr. Prabhala's research sparked my interest and led to a search for current information on vitamin D, how it works, how much we really need and how we get it. The following is a small part of the important information that I found.
Any discussion of vitamin D must begin with the discoveries of the Canadian-born dentist Weston A. Price. In his masterpiece Nutrition and Physical Degeneration, Dr. Price noted that the diet of isolated, so-called "primitive" peoples contained "at least ten times" the amount of "fat-soluble vitamins" as the standard American diet of his day.2 Dr. Price determined that it was the presence of plentiful amounts of fat-soluble vitamins A and D in the diet, along with calcium, phosphorus and other minerals, that conferred such high immunity to tooth decay and resistance to disease in nonindustrialized population groups.
Today another Canadian researcher, Dr. Reinhold Vieth, argues convincingly that current vitamin D recommendations are woefully inadequate. The recommended dose of 200-400 international units (IU) will prevent rickets in children but does not come close to the optimum amount necessary for vibrant health.3 According to Dr. Vieth, the minimal daily requirement of vitamin D should be in the range of 4,000 IU from all sources, rather than the 200-400 currently suggested, or ten times the Recommended Daily Allowance (RDA). Dr. Vieth's research perfectly matches Dr. Price's observations of sixty years ago!
Vitamin D From Sunlight Pick up any popular book on vitamins and you will read that ten minutes of daily exposure of the arms and legs to sunlight will supply us with all the vitamin D that we need. Humans do indeed manufacture vitamin D from cholesterol by the action of sunlight on the skin but it is actually very difficult to obtain even a minimal amount of vitamin D with a brief foray into the sunlight.4,5
Ultraviolet (UV) light is divided into 3 bands or wavelength ranges, which are referred to as UV-C, UV-B and UV-A.6 UV-C is the most energetic and shortest of the UV bands. It will burn human skin rapidly in extremely small doses. Fortunately, it is completely absorbed by the ozone layer. However, UV-C is present in some lights. For this reason, fluorescent and halogen and other specialty lights may contribute to skin cancer.
UV-A, known as the "tanning ray," is primarily responsible for darkening the pigment in our skin. Most tanning bulbs have a high UV-A output, with a small percentage of UV-B. UV-A is less energetic than UV-B, so exposure to UV-A will not result in a burn, unless the skin is photosensitive or excessive doses are used. UV-A penetrates more deeply into the skin than UV-B, due to its longer wavelength. Until recently, UV-A was not blocked by sunscreens. It is now considered to be a major contributor to the high incidence of non-melanoma skin cancers.7 Seventy-eight percent of UV-A penetrates glass so windows do not offer protection.
The ultraviolet wavelength that stimulates our bodies to produce vitamin D is UV-B. It is sometimes called the "burning ray" because it is the primary cause of sunburn (erythema). However, UV-B initiates beneficial responses, stimulating the production of vitamin D that the body uses in many important processes. Although UV-B causes sunburn, it also causes special skin cells called melanocytes to produce melanin, which is protective. UV-B also stimulates the production of Melanocyte Stimulating Hormone (MSH), an important hormone in weight loss and energy production.8
The reason it is difficult to get adequate vitamin D from sunlight is that while UV-A is present throughout the day, the amount of UV-B present has to do with the angle of the sun's rays. Thus, UV-B is present only during midday hours at higher latitudes, and only with significant intensity in temperate or tropical latitudes. Only 5 percent of the UV-B light range goes through glass and it does not penetrate clouds, smog or fog.
Sun exposure at higher latitudes before 10 am or after 2 pm will cause burning from UV-A before it will supply adequate vitamin D from UV-B. This finding may surprise you, as it did the researchers. It means that sunning must occur between the hours we have been told to avoid. Only sunning between 10 am and 2 pm during summer months (or winter months in southern latitudes) for 20-120 minutes, depending on skin type and color, will form adequate vitamin D before burning occurs.9
It takes about 24 hours for UV-B-stimulated vitamin D to show up as maximum levels of vitamin D in the blood. Cholesterol-containing body oils are critical to this absorption process.10 Because the body needs 30-60 minutes to absorb these vitamin-D-containing oils, it is best to delay showering or bathing for one hour after exposure. The skin oils in which vitamin D is produced can also be removed by chlorine in swimming pools.
The current suggested exposure of hands, face and arms for 10-20 minutes, three times a week, provides only 200-400 IU of vitamin D each time or an average of 100-200 IU per day during the summer months. In order to achieve optimal levels of vitamin D, 85 percent of body surface needs exposure to prime midday sun. (About 100-200 IU of vitamin D is produced for each 5 percent of body surface exposed, we want 4,000 iu.) Light skinned people need 10-20 minutes of exposure while dark skinned people need 90-120 minutes.11
Latitude and altitude determine the intensity of UV light. UV-B is stronger at higher altitudes. Latitudes higher than 30° (both north and south) have insufficient UV-B sunlight two to six months of the year, even at midday.12 Latitudes higher than 40° have insufficient sunlight to achieve optimum levels of D during six to eight months of the year. In much of the US, which is between 30° and 45° latitude, six months or more during each year have insufficient UV-B sunlight to produce optimal D levels. In far northern or southern locations, latitudes 45° and higher, even summer sun is too weak to provide optimum levels of vitamin D.13-15 A simple meter is available to determine UV-B levels where you live.
Vitamin D From Food What the research on vitamin D tells us is that unless you are a fisherman, farmer, or otherwise outdoors and exposed regularly to sunlight, living in your ancestral latitude (more on this later), you are unlikely to obtain adequate amounts of vitamin D from the sun. Historically the balance of one's daily need was provided by food. Primitive peoples instinctively chose vitamin-D-rich foods including the intestines, organ meats, skin and fat from certain land animals, as well as shellfish, oily fish and insects. Many of these foods are unacceptable to the modern palate.
For food sources to provide us with D the source must be sunlight exposed. With exposure to UV-B sunlight, vitamin D is produced from fat in the fur, feathers, and skin of animals, birds and reptiles. Carnivores get additional D from the tissues and organs of their prey. Lichen contains vitamin D and may provide a source of vitamin D in the UV-B sunlight-poor northern latitudes.16 Vitamin D content will vary in the organs and tissues of animals, pigs, cows, and sheep, depending on the amount of time spent in UV-B containing sunlight and/or how much D is given as a supplement. Poultry and eggs contain varying amounts of vitamin D obtained from insects, fishmeal, and sunlight containing UV-B or supplements. Fish, unlike mammals, birds and reptiles, do not respond to sunlight and rely on vitamin D found in phytoplankton and other fish. Salmon must feed on phytoplankton and fish in order to obtain and store significant vitamin D in their fat, flesh, skin, and organs. Thus, modern farm-raised salmon, unless artificially supplemented, may be a poor source of this essential nutrient.
Modern diets usually do not provide adequate amounts of vitamin D;17 partly because of the trend to low fat foods and partly because we no longer eat vitamin-D-rich foods like naturally reared poultry and fatty fish such as kippers, and herring. Often we are advised to consume the egg white while the D is in the yolk or we eat the flesh of the fish avoiding the D containing skin, organs and fat. Sun avoidance combined with reduction in food sources contribute to escalating D deficiencies. Vegetarian and vegan diets are exceptionally poor or completely lacking in vitamin D predisposing to an absolute need for UV-B sunlight. Using food as one's primary source of D is difficult to impossible.
Vitamin D Miracles Sunlight and vitamin D are critical to all life forms. Standard textbooks state that the principal function of vitamin D is to promote calcium absorption in the gut and calcium transfer across cell membranes, thus contributing to strong bones and a calm, contented nervous system. It is also well recognized that vitamin D aids in the absorption of magnesium, iron and zinc, as well as calcium.
Actually, vitamin D does not in itself promote healthy bone. Vitamin D controls the levels of calcium in the blood. If there is not enough calcium in the diet, then it will be drawn from the bone. High levels of vitamin D (from the diet or from sunlight) will actually demineralize bone if sufficient calcium is not present.
Vitamin D will also enhance the uptake of toxic metals like lead, cadmium, aluminum and strontium if calcium, magnesium and phosphorus are not present in adequate amounts.18 Vitamin D supplementation should never be suggested unless calcium intake is sufficient or supplemented at the same time.
Receptors for vitamin D are found in most of the cells in the body and research during the 1980s suggested that vitamin D contributed to a healthy immune system, promoted muscle strength, regulated the maturation process and contributed to hormone production.
During the last ten years, researchers have made a number of exciting discoveries about vitamin D. They have ascertained, for example, that vitamin D is an antioxidant that is a more effective antioxidant than vitamin E in reducing lipid peroxidation and increasing enzymes that protect against oxidation.19;20
Vitamin D deficiency decreases biosynthesis and release of insulin.21 Glucose intolerance has been inversely associated with the concentration of vitamin D in the blood. Thus, vitamin D may protect against both Type I and Type II diabetes.22
The risk of senile cataract is reduced in persons with optimal levels of D and carotenoids.23
PCOS (Polycystic Ovarian Syndrome) has been corrected by supplementation of D and calcium.24
Vitamin D plays a role in regulation of both the "infectious" immune system and the "inflammatory" immune system.25
Low vitamin D is associated with several autoimmune diseases including multiple sclerosis, Sjogren's Syndrome, rheumatoid arthritis, thyroiditis and Crohn's disease.26;27
Osteoporosis is strongly associated with low vitamin D. Postmenopausal women with osteoporosis respond favorably (and rapidly) to higher levels of D plus calcium and magnesium.28
D deficiency has been mistaken for fibromyalgia, chronic fatigue or peripheral neuropathy.1;28-30
Infertility is associated with low vitamin D.31 Vitamin D supports production of estrogen in men and women.32 PMS has been completely reversed by addition of calcium, magnesium and vitamin D.33 Menstrual migraine is associated with low levels of vitamin D and calcium.81
Breast, prostate, skin and colon cancer have a strong association with low levels of D and lack of sunlight.34-38
Activated vitamin D in the adrenal gland regulates tyrosine hydroxylase, the rate limiting enzyme necessary for the production of dopamine, epinephrine and norepinephrine. Low D may contribute to chronic fatigue and depression.39
Seasonal Affective Disorder has been treated successfully with vitamin D. In a recent study covering 30 days of treatment comparing vitamin D supplementation with two-hour daily use of light boxes, depression completely resolved in the D group but not in the light box group.40
High stress may increase the need for vitamin D or UV-B sunlight and calcium.41
People with Parkinsons and Alzheimers have been found to have lower levels of vitamin D.42;43
Low levels of D, and perhaps calcium, in a pregnant mother and later in the child may be the contributing cause of "crooked teeth" and myopia. When these conditions are found in succeeding generations it means the genetics require higher levels of one or both nutrients to optimize health.44-47
Behavior and learning disorders respond well to D and/or calcium combined with an adequate diet and trace minerals.48;49
Vitamin D and Heart Disease Research suggests that low levels of vitamin D may contribute to or be a cause of syndrome X with associated hypertension, obesity, diabetes and heart disease.50 Vitamin D regulates vitamin-D-binding proteins and some calcium-binding proteins, which are responsible for carrying calcium to the "right location" and protecting cells from damage by free calcium.51 Thus, high dietary levels of calcium, when D is insufficient, may contribute to calcification of the arteries, joints, kidney and perhaps even the brain.52-54
Many researchers have postulated that vitamin D deficiency leads to the deposition of calcium in the arteries and hence atherosclerosis, noting that northern countries have higher levels of cardiovascular disease and that more heart attacks occur in winter months.55-56
Scottish researchers found that calcium levels in the hair inversely correlated with arterial calcium-the more calcium or plaque in the arteries, the less calcium in the hair. Ninety percent of men experiencing myocardial infarction had low hair calcium. When vitamin D was administered, the amount of calcium in the beard went up and this rise continued as long as vitamin D was consumed. Almost immediately after stopping supplementation, however, beard calcium fell to pre-supplement levels.27
Administration of dietary vitamin D or UV-B treatment has been shown to lower blood pressure, restore insulin sensitivity and lower cholesterol.58-60
The Battle of the Bulge Did you ever wonder why some people can eat all they want and not get fat, while others are constantly battling extra pounds? The answer may have to do with vitamin D and calcium status. Sunlight, UV-B, and vitamin D normalize food intake and normalize blood sugar. Weight normalization is associated with higher levels of vitamin D and adequate calcium.61 Obesity is associated with vitamin-D deficiency.62-64 In fact, obese persons have impaired production of UV-B-stimulated D and impaired absorption of food source and supplemental D.65
When the diet lacks calcium, whether from D or calcium deficiency, there is an increase in fatty acid synthase, an enzyme that converts calories into fat. Higher levels of calcium with adequate vitamin D inhibit fatty acid synthase while diets low in calcium increase fatty acid synthase by as much as five-fold. In one study, genetically obese rats lost 60 percent of their body fat in six weeks on a diet that had moderate calorie reduction but was high in calcium. All rats supplemented with calcium showed increased body temperature indicating a shift from calorie storage to calorie burning (thermogenesis).61
The Right Fats The assimilation and utilization of vitamin D is influenced by the kinds of fats we consume. Increasing levels of both polyunsaturated and monounsaturated fatty acids in the diet decrease the binding of vitamin D to D-binding proteins. Saturated fats, the kind found in butter, tallow and coconut oil, do not have this effect. Nor do the omega-3 fats.66 D-binding proteins are key to local and peripheral actions of vitamin D. This is an important consideration as Americans have dramatically increased their intake of polyunsaturated oils (from commercial vegetable oils) and monounsaturated oils (from olive oil and canola oil) and decreased their intake of saturated fats over the past 100 years.
In traditional diets, saturated fats supplied varying amounts of vitamin D. Thus, both reduction of saturated fats and increase of polyunsaturated and monounsaturated fats contribute to the current widespread D deficiency.
Trans fatty acids, found in margarine and shortenings used in most commercial baked goods, should always be avoided. There is evidence that these fats can interfere with the enzyme systems the body uses to convert vitamin D in the liver.80
Vitamin D Therapy In my clinical practice, I test for vitamin-D status first. If D is needed, I try to combine sunlight exposure with vitamin D and mineral supplements.
Single, infrequent, intense, skin exposure to UV-B light not only causes sunburn but also suppresses the immune system. On the other hand, frequent low-level exposure normalizes immune function, enhancing NK-cell and T-cell production, reducing abnormal inflammatory responses typical of autoimmune disorders, and reducing occurrences of infectious disease.26;67;68-71 Thus it is important to sunbathe frequently for short periods of time, when UV-B is present, rather than spend long hours in the sun at infrequent intervals. Adequate UV-B exposure and vitamin-D production can be achieved in less time than it takes to cause any redness in the skin. It is never necessary to burn or tan to obtain sufficient vitamin D.
If sunlight is not available in your area because of latitude or season, sunlamps made by Sperti can be used to provide a natural balance of UV-B and UV-A. Used according to instructions, these lamps provide a safe equivalent of sunlight and will not cause burning or even heavy tanning. Tanning beds, on the other hand, are not acceptable as a means of getting your daily dose of vitamin D because they provide high levels of UV-A and very little UV-B.
If you have symptoms of vitamin-D insufficiency or are unable to spend time in the sun, due to season or lifestyle or prior skin cancer, consider adding a supplement of 1,000 IU daily. Higher levels may be needed but should be recommended and monitored by your health care practitioner after testing serum 25(OH)D. 1,000 iu can be obtained from a concentrated supplement or from 2 teaspoons of high quality cod liver oil. Both Carlson Labs and Solgar make a 1,000 IU vitamin-D supplement naturally derived from fish oil. (Do not attempt to obtain large amounts of vitamin D from cod liver oil alone, as this would supply vitamin A in excessive and possibly toxic amounts.)
Supplementation is safe as long as sarcoidosis, liver or kidney disease is not present and the diet contains adequate calcium, magnesium and other minerals.
Adequate calcium and magnesium, as well as other minerals, are critical parts of vitamin D therapy. Without calcium and magnesium in sufficient quantities, vitamin-D supplementation will withdraw calcium from the bone and will allow the uptake of toxic minerals. Do not supplement vitamin D and do not sunbathe unless you are sure you have sufficient calcium and magnesium to meet your daily needs. Weston Price suggested a minimum of 1,200-2,400 mg of calcium daily. Research suggests that 1,200-1,500 mg is adequate as a supplement for most adults, both men and women. (Magnesium intake should be half that of calcium.)
Two excellent sources of calcium in the human diet are dairy products and bone broths.2 If the diet does not contain sufficient amounts, you will need to add supplements. Bone meal, dolomite powder or calcium and magnesium tablets (Solgar or Kal), or calcium carbonate or lactate (Solgar, Kal, Now or Twinlab) are good calcium sources, inexpensive and safe.74 All of these brands have been tested and found to be free of lead and other heavy metals.
In my experience, the forms of calcium given in supplements should be equivalent to those found in food-bone meal as in the broth, calcium lactate as in milk products and dolomite as in lime used to process cornmeal products. These forms work most efficiently and with the least cost for bone repletion and general repletion of serum calcium status.75 If your diet is high in protein, calcium lactate or carbonate is probably a better source of calcium.
Read the label carefully to see how much elemental calcium is contained in each dose or tablet and make sure to take the right amount. If the label says a serving size is three tablets and contains 1,000 mg of calcium, you must take the full serving size to get that amount.
Higher amounts of calcium are important for anyone diagnosed with bone loss. Total daily calcium as a supplement may range from 1,500 mg to 2,000 mg depending on current bone status and your body size. Make the effort to split up your daily dose. Do not take all your calcium and magnesium once a day. A higher percentage of the calcium dose is absorbed if delivered in smaller, more frequent amounts.82
Expensive "chelated" calciums are not necessary if vitamin-D status is adequate. Taking calcium without sufficient D may cause other problems. Vitamin D controls the production of some calcium binding proteins, which are critical to normal calcium utilization.
Patients on vitamin-D therapy report a wide range of beneficial results including increased energy and strength, resolution of hormonal problems, weight loss, an end to sugar cravings, blood sugar normalization and improvement of nervous system disorders.
A paradoxical transient and non-complicating hypercalciuria (more calcium in the urine) may occur when the program is first initiated. This resolves quickly when adequate calcium and other minerals are consumed. Two other temporary side effects may occur during the first several months of treatment. One is daytime sleepiness after calcium is taken. This usually resolves itself after about one week. The other condition is the reappearance of pain and discomfort at the site of old injuries, a sign of injury remodeling or proper healing, which may take some time to clear up.
Toxicity Issues Vitamin programs usually omit vitamin D because of concerns about toxicity. These concerns are valid because vitamin D in all forms can be toxic in pharmacological (drug-like) doses. The dangers of toxicity have not been exaggerated, but the doses needed to result in toxicity have been ill defined with the unfortunate result that many people currently suffer from vitamin-D deficiency or insufficiency.
Abnormally high levels of vitamin D are indicated by blood levels exceeding 65 ng/ml or 162 nmol/l for extended periods of time and may be associated with chronic toxicity. Levels of 200-300 nmol/l or higher have been seen in several studies using supplementation and quickly resolve when supplementation is stopped. In such cases no long-term problems have been found. Long-term supplementation, without monitoring, may have serious consequences.
Before 1993, there was no affordable and available blood test for vitamin D. Now there is. To avoid problems, anyone engaging in levels of vitamin-D supplementation above 1,000 iu daily should have periodic blood tests. Don't forget to calculate your total vitamin-D intake from all sources-sunlight, food (including vitamin D in milk) and supplements, including cod liver oil.
Dr. Vieth suggests that critical toxicity may occur at doses of 20,000 IU daily and that the Upper Limit (UL) of safety be set at 10,000 IU, rather than the current 2,000 IU. While this may or may not be the definitive marker for safety in healthy persons with no active liver or kidney disease, there is no clinical evidence that long-term supplementation needs to be greater than 4,000 IU for optimal daily maintenance. This level would be somewhat lower when combined with exposure to UV-B.3;76
Doses used in clinical studies range from as little as 400 IU daily to 10,000-500,000 IU, given either as a single onetime dose or daily, weekly or monthly. Such large doses are given either as a prophylactic or because compliance is considered a problem. There seems to be some evidence that vitamin D works better, without toxicity, when given in lower, more physiologic doses of 2,000-4,000 IU daily rather than as 100,000 IU once a month. However, a single monthly dose of 100,000 IU did replete low levels of vitamin D in adolescents during winter.77
In my experience and that of other researchers, high, infrequent dosing can lead to problems. In one recent study, blood levels rose from low to extremely high, (more than 300 nmol/l) 2 to 4 hours after a 50,000 IU oral dose,65 and then slowly returned to pretreatment suboptimal levels. Clearly this must disrupt normal feedback mechanisms in D and calcium regulation.
Vitamin A can be administered in large, infrequent doses from consumption of animal or fish liver (or injections, used in third world countries to prevent blindness) because we have storage capacity for vitamin A in our livers. Vitamin D is different. It has only a small storage pool in the liver and peripheral fat. Our ancestors most definitely did not get vitamin D in large, infrequent doses. While vitamin D is stored in body fat, storage is not sufficient to maintain optimum blood levels during winter months.78 A single exposure to UV-B light will raise levels of vitamin D over the next 24 hours and then return to baseline or slightly higher within 7 days. Historically our requirements for D were satisfied by daily exposure to sunlight and/or daily intake from food. Lowfat diets and lack of seafood in the diet further contribute to the current worldwide insufficiency of vitamin D.
Sunlight on the Inside If any nutrient incorporates the properties of sunlight, it is vitamin D. The healthy "primitive" peoples that Dr. Price observed not only had broad, round, "sunny" faces, they also had sunny dispositions and optimistic attitudes towards life in spite of many hardships. Typical food intakes for peoples who have not been "civilized" range from 3,000 IU-6,000 IU. Modern intakes are paltry in comparison. The standard American diet provides vitamin D only in very low quantities.
The first step towards redressing some of the ills of civilized life-from depression to road rage, from cavities to osteoporosis-would be to get more light, inside or outside. Vitamin D adds sunlight to life from childhood through the golden years. In nonagenarians and centagenarians high levels of vitamin D in the blood and normal thyroid function were the strongest markers of health and longevity.79
Whether in the form of sunlight or dietary vitamin D from food and fish oils, optimal levels of the sunshine vitamin allow your body and mind to thrive, even during periods of stress.
About the Author
Krispin Sullivan, CN is a researcher and clinical nutritionist in practice in Woodacre, California. She is currently working on a book, Naked at Noon: The Importance of Sunlight and Vitamin D, to be published in 2001.
Instructions for physician monitoring of vitamin D, calcium and magnesium repletion are available from www.sunlightandvitamind.com or by contacting Krispin at krispin@krispin.com or 1-415-488-9636.
References
Sidebar Articles
Food Sources of Vitamin D USDA databases compiled in the 1980s list the following foods as rich in vitamin D. The amounts given are for 100 grams or about 3 1/2 ounces. These figures demonstrate the difficulty in obtaining 4,000 IU vitamin D per day from ordinary foods in the American diet. Three servings of herring, oysters, catfish, mackerel or sardines plus generous amounts of butter, egg yolk, lard or bacon fat and 2 teaspoons cod liver oil (500 iu per teaspoon) yield about 4,000 IU vitamin D-a very rich diet indeed!
Cod Liver Oil
Lard (Pork Fat)
Atlantic Herring (Pickled)
Eastern Oysters (Steamed)
Catfish (Steamed/Poached)
Skinless Sardines (Water Packed)
Mackerel (Canned/Drained)
Smoked Chinook Salmon
Sturgeon Roe
Shrimp (Canned/Drained)
Egg Yolk (Fresh)
(One yolk contains about 24 IU)
Butter
Lamb Liver (Braised)
Beef Tallow
Pork Liver (Braised)
Beef Liver (Fried)
Beef Tripe (Raw)
Beef Kidney (Simmered)
Chicken Livers (Simmered)
Small Clams (Steamed/Cooked Moist)
Blue Crab (Steamed)
Crayfish/Crawdads (Steamed)
Northern Lobster (Steamed)
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680
642
500
480
450
320
232
172
148
56
20
19
12
12
12
12
12
8
4
4
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The Many Forms of Vitamin D There are two types of vitamin D found in nature. Vitamin D2 is formed by the action of UV-B on the plant precursor ergosterol. It is found in plants and in was formerly added to irradiated cows milk. Most milk today contains D3. Vitamin D3 or cholecalciferol is found in animal foods. Both forms of vitamin D have been used successfully to treat rickets and other diseases related to vitamin D insufficiency.
Many consider D3 the preferred vitamin, having more biologic activity. Vitamin D3 as found in food or in human skin always comes with various metabolites or isomers that may have biological benefit. Dr. Price believed that there were as many as 12 metabolites or isomers in the vitamin D found in animal foods. When vitamin D is taken in the form of fish oil, or eaten in foods such as eggs or fish, these metabolites will be present. Both D2 and D3 can be toxic when taken inappropriately in large amounts.
When humans take in vitamin D from food or sunlight, it is converted first in the liver to the form 25(OH)D and then in the kidney to 1,25(OH)D. These active forms of vitamin D are available by prescription and are given to patients with liver or kidney failure or those with an hereditary metabolic defect in vitamin-D conversion.
Assessing Vitamin D Status Blood Testing: Currently there are two tests available for physicians to assess vitamin-D status. One is for the somewhat biologically active precursor 25(OH)D and another for 1,25(OH)D, the most active form, which is converted in the kidney and other organs. The latter is often normal in the blood even when the precursor 25(OH)D is low or deficient. The precursor is a better marker of vitamin-D status (or reserves) than the most active 1,25(OH)D form. It is the optimum level of 25(OH)D that is most strongly associated with general good health. (The test values given in this article are for 25(OH)D.) For many years the acceptable level of 25(OH)D has been at least 9 ng/ml (23 nmol/l). Some researchers believe that 20 ng/ml (50 nmol/l) should be the lower acceptable limit72 but Dr. Vieth presents a large amount of data to support his claim that this is far from optimal.3 Optimal levels are certainly at least 32 ng/ml (80 nmol/l) and preferably closer to 40 ng/ml (100 nmol/l).
Salivary pH Testing for calcium sufficiency: A method of assessing ionized calcium levels has been used by Weston Price, DDS and Carl Reich, MD and has confirmation in current research.73 After determining your serum-D status (testing) and undertaking a program of supplementation with vitamin D, calcium and magnesium, morning salivary pH should read 6.8-7.2. Lower values may indicate insufficient vitamin D (retest), or low levels of calcium in the diet. Look for pH paper with a range of 5.5-8.0 and increments of 0.2. PH papers with 0.5-degree increments are not sensitive enough to monitor progress. (Note: Do not take more than 1,000 IU of vitamin D without testing and supervision by a knowledgeable healthcare practitioner. Calcium can be adjusted within the ranges suggested. Several months of supplementation may be required to show positive results if the deficiency is severe and prolonged.)
Sources
References
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2. Price, Weston A. Characteristics of Primitive and Modernized Dietaries. Nutrition and Physical Degeneration. New Canaan, Connecticut: Keats Publishing, Inc 1989:256-81.
3. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety [see comments]. Am.J.Clin.Nutr. 1999;69:842-56.
4. Glerup H, Mikkelsen K, Poulsen L et al. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. J.Intern.Med. 2000;247:260-8.
5. Glerup H, Eriksen EF. [Vitamin D deficiency. Easy to diagnose, often overlooked (see comments)]. Ugeskr.Laeger 1999;161:2515-21. 6. Diffey BL. Solar ultraviolet radiation effects on biological systems. Phys.Med.Biol. 1991;36:299-328.
7. Moan J, Dahlback A, Setlow RB. Epidemiological support for an hypothesis for melanoma induction indicating a role for UVA radiation. Photochem.Photobiol. 1999;70:243-7.
8. Ranson M, Posen S, Mason RS. Human melanocytes as a target tissue for hormones: in vitro studies with 1 alpha-25, dihydroxyvitamin D3, alpha-melanocyte stimulating hormone, and beta-estradiol. J.Invest Dermatol.1988;91:593-8.
9. Sayre, R. M., Dowdy, J. C., Shepherd, J., Sadig, I., Bager, A., and Kollias, N. Vitamin D Production by Natural and Artificial Sources. 1998. Orlando, Florida, Photo Medical Society Meeting. 3-1-1998. Ref Type: Conference Proceeding
10. Holick MF. The cutaneous photosynthesis of previtamin D3: a unique photoendocrine system. J.Invest Dermatol. 1981;77:51-8.
11. Matsuoka LY, Wortsman J, Haddad JG, Kolm P, Hollis BW. Racial pigmentation and the cutaneous synthesis of vitamin D [see comments]. Arch.Dermatol. 1991;127:536-8.
12. Matsuoka LY, Wortsman J, Haddad JG, Hollis BW. In vivo threshold for cutaneous synthesis of vitamin D3. J.Lab Clin.Med. 1989;114:301-5.
13. Season, latitude, and ability of sunlight to promote synthesis of vitamin D3 in skin. Nutr.Rev. 1989;47:252-3.
14. Pettifor JM, Moodley GP, Hough FS et al. The effect of season and latitude on in vitro vitamin D formation by sunlight in South Africa. S.Afr.Med.J. 1996;86:1270-2.
15. Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J.Clin.Endocrinol.Metab 1988;67:373-8.
16. Bjorn LO, Wang T. Vitamin D in an ecological context. Int.J.Circumpolar.Health 2000;59:26-32.
17. Xue L, Lipkin M, Newmark H, Wang J. Influence of dietary calcium and vitamin D on diet-induced epithelial cell hyperproliferation in mice. J.Natl.Cancer Inst. 1999;91:176-81.
18. Moon J. The role of vitamin D in toxic metal absorption: a review. J.Am.Coll.Nutr. 1994;13:559-64.
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