How Much Vitamin D do you Really Need?

New research on vitamin D, also called the sunshine vitamin, is showing that most Americans are deficient

and that a lack of it may be contributing to breast cancer, colon cancer, osteoporosis, multiple sclerosis, fibromyalgia and other autoimmune diseases. In fact, if you work inside and use sunscreen you’re probably vitamin D deficient. This applies even more if you live in a northern latitude.

Vitamin D is in fact a hormone and it is the only hormone that is meant to be activated by sun exposure of the skin, not obtained through diet. But the ability to activate D is lost by the majority of us by age 40 and even a dark tan is no assurance that sufficient skin prohormone D activation has taken place. Many people spend their days indoors at schools and offices, live in northern regions were sunlight is sparse and use sunscreen. As low as SPF 15 blocks 99% of vitamin D. Right now, vitamin D supplementation seems like the only answer.

Deficiency is More Common Than Expected

By current standards, it is estimated that at least one billion people worldwide have inadequate vitamin D levels. Three quarters of American adults and teens are deficient. Even using the traditional standards for vitamin D adequacy, nearly half of US African-American women ages 15 to 49 were recently found to be vitamin D deficient. Further, 30% of African-American women who were given more than 2,000 IU of vitamin D from supplements were still found to have low vitamin D levels.

In another study, 34% of Canadians surveyed had inadequate vitamin D levels. In a Boston study of elderly people who took vitamin D supplements or drank 2–3 glasses of vitamin D-fortified milk, 80% were overtly or borderline vitamin D-deficient at the end of winter. 32% of medical students and doctors at Boston Hospital were found to be vitamin D deficient eventhough they were taking a multi-vitamin and drinking cow's milk daily, and eating salmon once a week. 73% of new mothers and 80% of their infants were vitamin D deficient. All mothers were taking prenatal vitamins and 90% were drinking 1-2 cups of cow's milk daily, and eating fish.

Faulty Recommended Doses

The renowned osteoporosis researcher, Dr. Robert Heaney, was a member of the 1997-2002 US Food and Nutrition Board, which set the official vitamin D intake guidelines. Dr. Heaney now reports, however, that his new research suggests these government recommendations were far too low. "When [the U.S. government] set the DRI in 1997, the amount of vitamin D recommended was based on the prevention of rickets only," said Robert Heaney. Fortified foods now give most people protection from rickets, but we may not be getting enough of the nutrient to benefit from its protective effects against cancer, stroke, depression and other diseases. In fact, Dr. Heaney now calculates that our typical diet combined with the current recommended supplemental D intake (which is only 200 IU, raising to 400 IU at age 51 and 600 IU for 71 years and older) would only provide for 15% of an ideal vitamin D blood level. Dr. Heaney himself now classifies the US Food and Nutrition Board recommendations as “falling into a curious zone between irrelevant and inadequate.” For individuals with extensive sunlight exposure, the governmental intake recommendations add little to their daily vitamin D production, and for those without ultraviolet exposure the recommended levels are insufficient to ensure desired D blood levels. Most Americans are severely deficient (including children), especially during the winter, when many northerners don't get the exposure to the sun that lets their bodies make vitamin D.

Humans Need & Use Much More Vitamin D then Ever Imagined

Researchers find we use and need substantially more vitamin D than previously thought. Dr. Robert Heaney has documented that our bodies use between 3,000 and 4,000 IU of vitamin D daily. Depending on many factors, including one’s sunlight exposure, skin pigmentation, weight, age, and existing vitamin D body stores, maintaining an adequate level of vitamin D can require anywhere from a few hundred to 4,000 or more International Units (IUs) of vitamin D daily. Some studies have shown that adults need 3000–5000 IU per day, and others indicate healthy adults can readily metabolize up to 10,000 IU vitamin D per day without harmful side effects. The need for supplemental vitamin D can vary a great deal from individual to individual and blood testing for vitamin D level is the best way to insure appropriate dosing.

Recommendations: Supplement with vitamin D3 at 1000–2000 IU daily (adults) if you do not get testing (or higher with testing, under the care of your healthcare practitioner). You may need higher levels than 1,000-2,000 IU/day to reap all the long-term health benefits vitamin D has to offer you, so talk it over with your healthcare provider.
You will want to avoid buying swallowable tablets as they will not be absorbed as well as gelcaps or liquid.

If possible go outside in strong sun anywhere from 5-30 minutes a day (darker pigmentation needs full 30 minutes). Do this a minimum of twice a week, in 10-3 pm sun, without sunscreen. If you live in a northern region, you will need to supplement from around September-April or all year round if you avoid the sun or wear sunscreen all summer. Adjust your supplement according to how much sun you get.

Vitamin D Toxicity Fears Unwarranted

In 1999, Dr. Reinhold Vieth indirectly asked the medical community to produce any evidence 10,000 units of vitamin D a day was toxic, saying "Throughout my preparation of this review, I was amazed at the lack of evidence supporting statements about the toxicity of moderate doses of vitamin D." He added: "If there is published evidence of toxicity in adults from an intake of 10,000 IU per day, and that is verified by the 25(OH)D concentration, I have yet to find it.".
Like most medication, cholecalciferol is certainly toxic in excess, and, like Coumadin, is used as a rodent poison for this purpose. Animal data indicates signs of toxicity can occur with ingestion of 20,000 IU, while the oral LD50 (the dose it takes to kill half the animals) for cholecalciferol in dogs is about 3,520,000 IU. This would be equivalent to a 110-pound adult taking 176,000,000 IU or 440,000 of the 400 unit cholecalciferol capsules.
Vieth reports human toxicity probably begins to occur after chronic daily consumption of approximately 40,000 IU/day (100 of the 400 IU capsules). Heavy sun exposure when combined with excessive supplement use is a theoretical risk for vitamin D toxicity, but if such a case has been reported, I am not aware of it.

Physician ignorance about vitamin D toxicity is widespread. A case report of four patients appeared in the 1997 Annals of Internal Medicine, accompanied by an editorial warning about vitamin D toxicity. However, careful examination of the patients reveals that both papers are a testimony to the fact that incompetence about vitamin D toxicity can reach the highest levels of academia.

Cholecalciferol, Not Erocalciferol, Is Safe

Although there are documented cases of pharmacological overdoses from ergocalciferol, the only documented case of pharmacological—not industrial—toxicity from cholecalciferol that can be found in literature was intoxication from an over-the-counter supplement called Prolongevity. On closer inspection, it seemed more like an industrial accident but it was interesting because it gave some idea of the safety of cholecalciferol. The capsules consumed contained up to 430 times the amount of cholecalciferol contained on the label(2,000 IU). The man had been taking between 156,000–2,604,000 IU of cholecalciferol a day (equivalent to between 390–6,500 of the 400 unit capsules) for two years. He recovered uneventfully after proper diagnosis, treatment with steroids, and sunscreen.

The Sun Supplies 10,000 IU of Vitamin D

The single most important fact anyone needs to know about vitamin D is how much nature supplies if we behave naturally, e.g., go into the sun. Humans make 10,000 units of vitamin D within 20-30 minutes of full body exposure to the sun, what is called a minimal erythemal dose. Vitamin D production in the skin occurs within minutes and is already maximized before your skin turns pink.

Fear of the fatal form of skin cancer, malignant melanoma, keeps many people out of the sun. The problem with the theory is that the incidence of melanoma continues to increase dramatically although many people have been completely avoiding the sun for years. This is not to say sunburns are safe, they are not. Brief, full-body sun exposure (minimal erythemal doses) may slightly increase your risk of skin cancer but it is a much smarter thing to do than dying of vitamin D deficiency.


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