Vitamin D is getting more attention now that some experts are recommending higher daily intake. The currently recommended daily vitamin D intake is 400 IU/day. Some experts say that this is too low. They say that vitamin D is more important than calcium for bone health and that vitamin D has other potential health benefits. The jury is still out on the optimal intake of vitamin D, but many experts recommend 400 to 800 units a day. Keep in mind that ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) are no longer considered equivalent. Cholecalciferol is much more potent than ergocalciferol. Positive fracture prevention studies have used cholecalciferol. If you wish to purchase a Vitamin-D supplement.
   Very few foods naturally contain vitamin D or are fortified. Fish such as wild salmon (360 IU per 3.5-ounce serving), mackerel, and sardines are good sources of vitamin D3, while fortified foods include milk (100 IU per 8-ounce serving), orange juice (100 IU per 8-ounce serving), and some breads and cereals provide D2.
   Low blood levels of vitamin D appear to increase the risk of heart attacks in middle-aged and older men. Ecological studies have shown that death from heart disease is increased at higher latitudes, during the winter, and at lower altitudes, all of which are associated with low vitamin D levels. However, cold temperature can play a factor by increasing coagulation of the blood.

Daily need for vitamin D
Dietary reference intakes for Vitamin D were determined based on blood 25 hydroxyvitamin D concentration sufficient to prevent rickets and osteomalacia. Vitamin D deficiency is associated with cancers, diabetes, heart disease, periodontal diseases and influenza. Vitamin D deficiency has many causes including low levels in foods, latitude, solar-irradiation, atmospheric-pollution, skin-pigmentation, clothing, sunscreen-use and increased time spent indoors. Plasma 25-OHD concentration range from 25-138 nmol/L. Plasma 25-OHD  greater than 75 nmol/L improves calcium absorption, suppresses PTH elevation, reduces the risks of bone loss and fractures. Vitamin D supplementation with 10 microg/d is insufficient to lower fracture risks. Combined Vitamin D and calcium supplementation in higher doses has been found superior to Vitamin D alone to increase bone-mass in adolescents and to reduce non-vertebral fractures in postmenopausal women. The optimal level of Vitamin D has yet to be established.

Vitamin D levels
Many U.S. teenagers -- including half of African Americans -- would be considered vitamin D-deficient if the definition of deficiency were changed to what many experts recommend. People are considered to have an overt deficiency in vitamin D when blood levels drop below 11 nanograms per milliliter (ng/mL), but there is debate over how the optimal vitamin D level should be defined. Some researchers consider a level of 30 ng/mL or higher to be desirable for overall health, and many argue that the cutoff for deficiency should be 20 ng/mL. Vitamin D is naturally synthesized in the skin when it is exposed to sunlight. This process is less efficient in people with darker skin, which is one reason African Americans are at higher risk of deficiency. Overweight children and adults appear to be at elevated risk because vitamin D is stored in body fat. The more vitamin D that gets taken up by fat tissue, the less active vitamin there is in the blood. Pediatrics, March 2009.
   Persons with limited exposure to ultraviolet B light may not receive enough vitamin D. Some scientists believe that optimal serum 25-hydroxyvitamin D [25(OH)D] should be ≥80 nmol/L.

Vitamin D overdose and toxicity
Vitamin D is a fat soluble vitamin stored predominantly in the liver. High amounts of vitamin D intake could also lead to storage of the vitamin in fatty tissues. Vitamin D is not excreted in the urine or stools or otherwise eliminated as easily as water soluble vitamins such as vitamin C.  Vitamin D overdose can lead to toxicity such as very high levels of calcium in the blood called hypercalcemia. Hypercalcemia caused by excess Vitamin D can lead to unpleasant conditions such as kidney stones and kidney failure.
   Those predisposed to vitamin D toxicity have a high calcium intake, decreased kidney function, diminished estrogen levels, the existence of sarcoidosis or other vitamin D-hypersensitivity syndromes associated with overproduction of 1,25(OH)2D. Of course, vitamin D overdose or toxicity can easily result from excess intake of vitamin D supplements. Some people may be taking several hundred units of vitamin D through a supplement, and not realize their multivitamin or other supplement product also has vitamin D.
   Vitamin D overdose can lead to vitamin D toxicity such as nausea, vomiting, poor appetite, weakness, and weight loss. Vitamin D overdose can also raise blood levels of calcium, causing mental status changes such as confusion. High blood levels of calcium, known as hypercalcemia, can cause heart rhythm abnormalities. Calcinosis, the deposition of calcium nd phosphate in soft tissues like the kidney can be caused by vitamin D toxicity.

Vitamin D deficiency
Vitamin D deficiency may be a common but unrecognized problem among U.S. adolescents. Researchers found that among 11- to 18-year-olds living in Boston, nearly one-quarter were deficient in vitamin D, a nutrient that aids in calcium absorption and is vital for healthy bone development. Another form of vitamin D is calcitriol. The problem is preventable with an adequate diet and time outdoors. The body naturally synthesizes vitamin D when the skin is exposed to the sun, and milk and certain other foods, including many breakfast cereals, are fortified with the vitamin. But U.S. children increasingly fill up on soft drinks at the expense of milk, and spend more time in front of the TV or computer than outdoors. Soft drink, juice and iced tea intake are related to a greater risk of vitamin D deficiency. On the other hand, adolescents who drink milk and eat cereal are less likely to be low on the vitamin. People with a low level of vitamin D in the blood have poorly functioning insulin-producing cells and show a poor response to insulin, even when their blood sugar levels are normal.

More than three out of four Americans aren't getting enough vitamin D, a study in the Archives of Internal Medicine shows, which could be boosting their risk of cancer, cardiovascular disease, and early death. Archives of Internal Medicine, March 23, 2009.

Vitamin D recommended daily dosage
The recommended daily intake of vitamin D is 200 iu for adults younger than 50 years and 600 iu for those older than 70 years. Vitamin D supplementation is especially important in elderly persons because skin synthesis and absorption of vitamin D may be impaired.

Vitamin D and osteoporosis, bone health, proper dosage
Vitamin D3 (cholecalciferol) is crucial for optimal bone health. Vitamin D increases intestinal absorption of calcium and phosphorus. The major source of vitamin D for both children and adults is exposure of the skin to sunlight. Season, latitude, skin pigmentation, sunscreen use, clothing and aging can dramatically influence the synthesis of vitamin D in the skin. Very few foods naturally contain vitamin D or are fortified with vitamin D. Serum 25-hydroxyvitamin D [25(OH)D; calcifediol] is the best measure of vitamin D status. Vitamin D deficiency [as defined by a serum 25(OH)D level of less than 20 ng/mL] is pandemic. This deficiency is very prevalent in patients with osteoporosis. Vitamin D deficiency causes osteopenia, osteoporosis and osteomalacia, increasing the risk of fracture. Vitamin D deficiency causes muscle weakness, increasing the risk of falls and fractures, and should be aggressively treated with pharmacological doses of vitamin D. Vitamin D sufficiency can be sustained by sensible sun exposure or ingesting at least 800-1000IU of vitamin D(3) daily.
   Although most doctors and researchers agree that vitamin D supplementation is useful in reducing the risk for osteoporosis, not all studies support this viewpoint. We have included on such vitamin D and bone density study below.

A Randomized Controlled Trial of the Effects of Calcium with or Without Vitamin D on Bone Structure and Bone Related Chemistry in Elderly Women with Vitamin D Insufficiency.
J Bone Mineral Res. 2008 April. Zhu K, Bruce D, Austin N, Devine A, Ebeling PR, Prince RL.
There are few data on the relative effects of calcium supplementation with or without extra vitamin D on bone density and osteoporosis in patients selected for low vitamin D status. The aim of this study is to evaluate the relative importance of vitamin D and calcium treatment on bone density and bone related chemistry in elderly women with vitamin D insufficiency. 302 elderly women with serum 25OHD concentrations less than 60 nmol/L participated in a 1 year randomized, double-blind, placebo-controlled trial. All subjects received 1000 mg calcium citrate per day with either 1000 IU ergocalciferol (vitamin D2 or identical placebo (control). In patients with a baseline calcium intake of 1000 mg per day and vitamin D insufficiency, vitamin D(2) 1000 IU for one year has no extra beneficial effect on bone structure, bone formation markers or intestinal calcium absorption over an additional 1000 mg of calcium. Vitamin D supplementation adds no extra short term skeletal benefit to calcium citrate supplementation even in women with vitamin D insufficiency.

Older people can prevent fractures by taking vitamin D supplements as long as they use a high enough dose-and keep taking it. A dose of about 800 IU per day of vitamin D3 is recommended, according to Dr. Heike A. Bischoff-Ferrari of the University of Zurich. Dr. Heike A. Bischoff-Ferrari pooled the results of 12 randomized controlled trials of oral vitamin D supplementations. Overall, the supplements cut the risk of any non-vertebral fracture by 14 percent, and of hip fractures by 9 percent. While quantities below 400 IU a day had no effect on fracture risk, people who consumed more than 400 IU daily had a 20 percent lower risk of any type of fracture and an 18 percent lower risk of hip fracture. Archives of Internal Medicine, March 23, 2009.

Vitamin D may prevent alcohol-related bone loss
Numerous cell, animal and human studies have shown that heavy drinking leads to bone loss. New research conducted in rats now suggests that vitamin D or the anti-osteoporosis drug Boniva (ibandronate) can prevent alcohol-related bone loss caused by regular binge drinking. In a rat study, Dr. Frederick H. Wezeman from Loyola University Medical Center, Maywood, Illinois, observed that large quantities of alcohol, similar to those taken in by binge drinkers, led to a significant decrease in bone mineral density and bone strength. Treating the rats, before alcohol exposure, with a dose of vitamin D (2,500 IU daily) prevented alcohol-induced bone loss, significantly increasing bone mineral density in the tibia (shin bone) and lower spine. In addition, pretreatment with a single dose of Boniva (120 micrograms) also prevented alcohol-induced bone loss.

Vitamin D reduces the risk of Hip fracture
Vitamin D deficiency is quite common in cases of hip fractures. A look-back study of 548 patients older than 60 years of age who were admitted at South Glasgow University Hospital in Scotland in the previous 4 years, showed that 97 percent of the patients had Vitamin D levels below normal. Dr. Gallacher, lead researcher and consultant endocrinologist at the hospital said: ''Although the numbers were too small to justify extensive subgroup analyses the study appears to demonstrate that vitamin D inadequacy represents a significant correctable risk factor for fragility fracture and perhaps specifically for the hip."
    Most elderly patients do not get enough Vitamin D through sun exposure, particularly in cold climates with long winters. Vitamin D can be supplemented by taking a multivitamin and mineral complex, through cod liver oil, or through Vitamin D fortified foods. A Vitamin D supplement (preferably natural Vitamin D3) or multivitamin product with 400 to 800 units should be adequate. Sitting by the window or taking walks outside could be helpful. Getting exposed to sunlight or any type of light is also beneficial since it helps reset the circadian clock and helps one achieve a deeper sleep at night.

Vitamin D and cancer
Certain amounts of vitamin D may be able to reduce the risk for breast cancer and colorectal cancer cases in the United States, according to two studies by researchers at the Moores Cancer Center at the University of California, San Diego, and colleagues at other centers. In one study, the researchers reviewed two previous studies of 1,760 women and found that those with the highest blood levels of 25-hydroxyvitamin D, or 25(OH)D, had the lowest risk of breast cancer. The vitamin D serum level associated with a reduction in risk could be maintained by taking 1,000 international units of vitamin D3 daily, plus, spending 10 to 15 minutes a day in the sun. In the second study, researchers reviewed data from 1,448 people who took part in five previous colorectal cancer studies. Raising the serum level of 25-hydroxyvitamin D reduces the incidence rates of colorectal cancer. The study was published online Feb. 6, 2007 in the American Journal of Preventive Medicine.

June 2007 - Large doses of vitamin D may reduce the risk of cancer, according to a four-year U.S. study involving more than 1,100 women over the age of 55 in rural Nebraska. Women who took calcium and a dose of vitamin D almost three times the government's recommended daily intake for middle-aged adults saw a 60 percent lower incidence of cancer than women who were not taking the vitamin. The study was conducted by researchers at the Creighton University School of Medicine in Omaha, Nebraska.

Forms of vitamin D
There are two major dietary forms of vitamin D - vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is the form most often added to milk and other foods as well as the form most often used in nutritional supplements. Vitamin D3 in nutritional supplements is most often derived from fish liver oil or lanolin. Both D2 and D3 are capable of being converted to active vitamin D in the body.

Vitamin D hormone supplement questions
Q. Do you feel the USDA's recommended intake of 200 IU/day for adults is antiquated and too low, especially for folks like me and mine living in the northern latitudes? What are plausibly better doses for adults, along with kids and seniors?
   A. It would seem safe to have 400 to 600 units a day, but higher dosage safety and vitamin D toxicity has yet to be determined. Many people are taking 2,000 units or even higher amounts, and we are concerned that these could cause vitamin D overdose and toxicity.

Q. Since D3, 25(OH)D3, 1a,25(OH)2D3 and 24R,25(OH)2D3 are fat soluble, how long do they "stick around"? Is there evidence that we store them for later usage, to wit, when the sun hasn't shone in weeks? Would this be an argument against D3 supplements?
   A. We do store vitamin D, we are not exactly sure for how long.

3) Can you comment on how the "demonization" of the sun (Helios weeps) has impacted people's health, regarding decreased D3 synthesis in the skin? (Not to mention Seasonal Affect Disorder.) Obviously, too much sun is bad, but direct sunlight a few times a week for 20 minutes or so is actually quite healthy, right?
   A. The public has been told of the sun causing skin cancer, but the public has also heard of the benefit of sun exposure for vitamin D production, hence it seems the right balance has been put out.

How significant do you feel the research is showing that getting enough D3, via the sun and/or supplementation, plays a role in the prevention of certain cancers, Multiple Sclerosis, type-1 diabetes, psoriasis, and bone loss resulting from Crohn's disease? Is there enough evidence warranting supplementation in your opinion?
    Each medical doctor and researcher has their own opinion on this topic, and it is controversial, but it would appear that taking an extra 200 to 400 units a day is reasonable unless someone is exposed to an hour of sun on a daily basis. It is difficult to know for certain at this time the role of vitamin D supplementation in cancer prevention.

Are there any interactions between Tribulus Terrestris Extract and vitamin D pills that you know of?
    Not that we know of.

I have been prescribing vitamin D in various forms for years. Generally I only get a baseline level -- a 25-hydroxy vitamin D level -- in patients not already on vitamin D either (a) to convince the patient that vitamin D is necessary or (b) to convince some 3rd party, eg, payor, that vitamin D is necessary. Actually, if the serum calcium level is anywhere less than about 9.5 one can assume that some vitamin D can be used; once vitamin D is begun rather than following the vitamin D level one follows the calcium level, wanting to keep the patient just shy of hypercalcemia -- ie, around a calcium level of 10.1-10.2. There really is no known top limit for any of the measures of vitamin D as long as the patient is not hypercalcemic. Several years back I ran into a fair number of patients who had placed themselves on calcium plus vitamin D tablets -- or had been placed on the same by their physicians -- in the absence of knowing the serum calcium level, and these patients would be hypercalcemic -- presenting with irritability and memory loss. I put almost ALL pain patients, almost ALL cancer patients, and almost ALL fracture patients on vitamin D unless the serum calcium level is known to be high. While the data is less conclusive and more complicated, I also put almost ALL hyponatremic patients on vitamin D (as well as vitamin B12) as enhancing calcium absorption almost always raises serum sodium. So, the bottom line is that getting a calcium level -- most practically as part of a comprehensive metabolic profile -- is more important that getting a vitamin D level unless someone -- patient or payor -- needs to be convinced of the benefit -- even though it is close to impossible to get too much vitamin D as long as hypercalcemia has not been produced. With cancer patients, if one is trying to keep both vitamin D and calcium at the highest safe levels simultaneously, then one can get a 25-hydroxy vitamin D level followed later by that plus a 1,25-dihydroxy vitamin D level, so that one can figure out the optimal mix of vitamin D2 and vitamin D3 to recommend; if one is trying this approach then getting a 24-hour urine for calcium at least once a year also would be wise -- although, most practically, one can just maintain the serum magnesium level at the high end of the range in terms of avoiding producing kidney stones. I anticipate that you will want to work all this out for yourself, but perhaps my comments will give you some starting places for your further study.
   Your email illustrates the various viewpoints on vitamin D testing and treatment. I am not sure we need to get a test in order to convince the insurance companies since this vitamin costs so little and the testing itself is more expensive than several years of vitamin D supplementation.