Vitamin D is also referred to as the sunshine vitamin, since the body, when exposed to sunlight, can manufacture this nutrient from sunshine on your skin using cholesterol from your body [which naturally produces all that you require] to do so. Please remember that this can be achieved in about 15 minutes by fair skinned people, while dark skinned people, because of the pigmentation need about 30 minutes to reach the same level of manufacture. The sunlight needed for this process is pure unfiltered sunlight.
     Vitamin D consists of a group of similar molecules called vitamers, which are involved in calcium homeostasis and in bone metabolism. The human body makes vitamin D by the effects of ultraviolet light on the skin’s cholecalciferol also known as D3. Plants make a slightly different version of vitamin D called D2; however this form of vitamin D is also used by humans - veg(etari)ans are not known for vitamin D deficiency or ailments linked to lack of this nutrient.

REQUIRED FOR:
     Helps with increasing the absorption of calcium, assists in the growth and integrity of bone, and promotes strong teeth. Vitamin D plays an important role in calcium and phosphorus homeostasis by regulating bone resorption, affecting absorption of calcium in the gut, and by regulating calcium losses in urine.
1. In the kidney vitamin D works with estrogen to regulate renal tubular reabsorption of calcium and phosphorus. In bones, vitamin D works in conjunction with PTH to regulate the release of calcium and phosphorus from the bones into the bloodstream as well as assisting in a healthy heart and nervous system.
2. Vitamin D also plays a genetic role by regulating the gene coding for calcium binding protein known as Calbindin. Vitamin D’s genetic role has been confirmed in over 50 genes extending beyond balancing mineral metabolism. New findings have confirmed direct effects by vitamin D on various nuclear receptors of different cells such as those of the prostate, liver, thyroid, and brain.
3. Cells of the prostate gland respond to vitamin D levels.
These findings have lead to new potential chemotherapeutic treatments targeting specific lesions on cancer cells using doses of 1alpha25 (OH) 2D3.
4. Another group of cells directly affected by vitamin D levels appear to be the T helper cells of the immune system. Other studies have also shown great promise in assisting psoriasis, thyroid function as well as normal blood clotting.
5. Polymorphisms in vitamin D receptors in brain cells (due to low levels of vitamin D early in life), also appear to be linked to schizophrenia.

DEFICIENCY:
     Symptoms include Rickets in children - resulting in bent legs - and osteomalacia in adults resulting from poor ossification of bone tissue, resulting in soft, weak bones that bend readily as well as low serum calcium concentrations and tetany. In adults, the shortage causes loss of minerals from the bones, (osteomalacia) where the bones are sore, tender, and weak muscles [with twitching and convulsions] and the possibility of deafness developing.
     Less severe vitamin D deficiency can result in hyperparathyroidism and increased bone turnover leading to bone loss and osteoporosis. Osteoporosis may appear when protein is also lost from the bone (osteoperpsis rates are much higher in those who consume dairy products fortified with vitamin D).
     In short supply is also linked to having a burning sensation in the mouth and throat, diarrhea, insomnia and visual problems. Vitamins D deficiency is relatively "common" in the U.S. Studies have demonstrated that nearly 60% of people over 70 years are vitamin D deficient (under new increased RDA levels designed to get people to buy more pills).
     Furthermore, the average daily intake of vitamin D in the United States is only 30% of the RDA. A deficiency can result from inadequate intake [low consumption of plant matter], limited exposure to sunlight, kidney and/or liver dysfunctions which inhibit conversion of vitamin D to its metabolically active forms, or fat-malabsorption syndromes.

Recommended Daily Allowance:
Men / Women:	200IU [5mcg]
Adults over 50:	400IU [10mcg]
Adults over 70:	600IU [15mcg]

     *In light of the recent -sketchy- findings many "experts and professional associations" have pushed for an increase in the recommended amount of vitamin D intake to "combat" diseases (which are associated with the consumption of animal products). These "experts" call for an increase in of vitamin D intake to 1000IU for an adult which is substantially higher than the current recommendation of 200IU. This has greatly delighted and benefited the animal agrikulture sector, as much of the D supplements are in the D3 (animal derived) form.
     The promotion of D supplements has also been a heavy burden on health care systems as people have unthinkingly flooded laboratories with requests to have costly blood work-ups done to check D levels...rather than eat a healthy balanced diet. Increases in both the recommended dose as well as in the upper tolerable intakes are currently under review by the Institute of Medicine and changes in favour of increases are expected by the "scientific" community.
     NO studies, predictably, have been conducted on any vegetarian population (despite "expert" claims that vegetarians are "at risk" of "deficiencies") to see if there is indeed any merit to increase the levels of D above 200IU. The production of calcitriol is regulated by enzymes which lead to a feedback inhibition mechanism. Efficacy of absorption for vitamin D is 50% from the diet.

TOXICITY:
     This vitamin is fat-soluble so can accumulate in the body and overdoses are dangerous. Some clinical guidelines for toxicity are sometimes set as 5,000 to 10,000IU per day to cause toxicity, but other researchers place the value much higher to reach toxicity.
     You are however advised to keep your supplement intake to no more than 600 iu per day. Having too much vitamin D in your system could leave a too elevated calcium level, a lower appetite, increased thirst, nausea, vomiting, drowsiness, abdominal pain. These symptoms were commonly seen during decades when parents would give their children doses of cod liver oil to prevent rickets.
     A long-term effect of too much vitamin D is the deposit of calcium in soft tissues of the body including the blood vessel walls and kidneys where it can cause serious damage.

ENHANCED BY:
     Check to have vitamin A around this vitamin as well as calcium and phosphorus.

WHEN MORE MAY BE REQUIRED:
     When you consume little plant foods, are very seldom exposed to sunlight, or if you always wear sunscreens with a SPF factor higher than 8, you might need extra vitamin D. Consumption of alcohol may alter absorption of vitamin D and may lead to deficiency. People with compromised kidneys or liver are at risk of too little of this vitamin, since the kidneys and liver are required to activate this vitamin in processes taking place in those organs. Obese individuals are also at high risk of vitamin D deficiency. Though the skin is able to manufacture vitamin D normally, it is not able to enter into the circulation as well as it does in non-obese persons. Obesity is directly tied to the consumption of animal products. Kidneys and livers are often over-burdened by the consumption of animal products and the need to eliminate their vast quantities of toxic substances from the body.

INTERESTING NOTES:
     Since vitamin D works on specific target tissues, and does not have to be supplied by the diet, it is by definition a hormone, and not truly a vitamin. The vitamin D hormone usually functions as a steroid. Ironically, from a supplemental point of view, milk is fortified with plant-derived D2. Humans do not to take vitamin D supplements to be healthy, they simply need to eat much less animal products which cause nothing but problems.

FOOD SOURCES:
Plant matter, such as dark leafy vegetables.