Your body makes vitamin D when it's exposed to sunlight. In fact, 80 to 100 percent of the vitamin D we need comes from the sun. The sun exposure that makes our skin a bit red (called 1 minimum erythemal dose) produces the equivalent of 10,000 to 25,000 international units (IU) of vitamin D in our bodies.
The problem is that most of us aren't exposed to enough sunlight.
Overuse of sunscreen is one reason. While these product help protect against skin cancer--they also block a whopping 97 percent of your body's vitamin D production.
If you live in a northern climate, you're not getting enough sun (and therefore vitamin D), especially during winter. And you're probably not eating enough of the few natural dietary sources of vitamin D: fatty wild fish like mackerel, herring and cod liver oil or porcini mushrooms.
In addition, aging skin produces less vitamin D--the average 70-year-old person creates only 25 percent of the vitamin D that a 20 year-old does. Skin color makes a difference, too. People with dark skin also produce less vitamin D. And I've seen very severe deficiencies in Orthodox Jews and Muslims who keep themselves covered all the time.
With all these causes of vitamin D deficiency, you can see why supplementing with enough of this vitamin is so important. Unfortunately, you aren't really being told the right amount of vitamin D to take.
The government recommends 200 to 600 IU of vitamin a day. This is the amount you need to prevent rickets, a disease caused by vitamin D deficiency. But the real question is: How much vitamin D do we need for OPTIMAL health? How much do we need to prevent autoimmune diseases, high blood pressure, fibromyalgia, chronic muscle pain,(vii) depression, osteoporosis and even cancer?
The answer is: Much more than you think.
Recent research by vitamin D pioneer Dr. Michael Holick, Professor of Medicine, Physiology, and Dermatology at Boston University School of Medicine, recommends intakes of up to 2,000 IU a day -- or enough to keep blood levels of 25 hydroxy vitamin D at between 75 to 125 nmol/L (nanomoles per liter).(viii) That may sound high, but it's still safe: Lifeguards have levels of 250 nmol/L without toxicity.
Our government currently recommends 2,000 IU as the upper limit for vitamin D -- but even that may not be high enough for our sun-deprived population! In countries where sun exposure provides the equivalent of 10,000 IU a day and people have vitamin D blood levels of 105 to 163 nmol/L, autoimmune diseases(like multiple sclerosis, type 1 diabetes, inflammatory bowel disease, rheumatoid arthritis and lupus) are uncommon. (Divide nmol/L by 2.5 to get ng/ml, the units used in USA. Jim)
Don't be scared that amounts that high are toxic: One study of healthy young men receiving 10,000 IU of vitamin D for 20 weeks showed no toxicity.(ix)
You might have seen a recent study in the Journal of the American Medical Association that shows that a single high dose of 500,000 Units of vitamin D3 (one year's worth of vitamin D) increased the risk of falls and fractures in elderly woman.(x) Does this mean that vitamin D doesn't prevent fractures or falls? Absolutely not! (Yes, many smart scientists can be very very stupid as I found when I worked among Ivy League Harvard and MIT scientists and engineers. Jim)
The design and logic of the study were completely wrong. As a friend once said, "The well meaning are often ill doing."
Imagine a study that gave people a year's worth of vitamin A, or iron (both are nutrients that are stored in the body like vitamin D) in one dose. The vitamin A would cause immediate liver failure and death. In fact, the way the Inuit used to kill explorers in the Arctic was to feed them polar bear liver, which gave them toxic doses of vitamin A. A year's worth of iron in one dose would cause severe intestinal problems and iron poisoning.
Biologically we understand why a single high dose of vitamin D may cause problems. A single high dose induces protective mechanisms that reduce the available vitamin D by increasing the activity of enzymes that cause the vitamin D to be broken down by the body. (xi) The body requires a balance of the right nutrients at the right dose at the right time. No one would eat a year's worth of anything in one day and expect it to be healthy. ...
6 Tips for Getting the Right Amount of Vitamin D
Unless you're spending all your time at the beach, eating 30 ounces of wild salmon a day, or downing 10 tablespoons of cod liver oil a day, supplementing with vitamin D is essential. The exact amount needed to get your blood levels to the optimal range (100 to160 nmol/L) will vary depending on your age, how far north you live, how much time you spend in the sun and even the time of the year. But once you reach optimal levels, you'll be amazed at the results.
For example, one study found that vitamin D supplementation could reduce the risk of getting type 1 diabetes by 80 percent.(xii) In the Nurses' Health Study (a study of more than 130,000 nurses over 3 decades), vitamin D supplementation reduced the risk of multiple sclerosis by 40 percent.(xiii),(xiv)
I've seen many patients with chronic muscle aches and pains and fibromyalgia who are vitamin D deficient--a phenomenon that's been documented in studies. Their symptoms improve when they are treated with vitamin D. A Danish study of Arabic women with fibromyalgia found significant vitamin D deficiency and recovery with replacement of vitamin D.(xv)
Finally, vitamin D has been shown to help prevent and treat osteoporosis. In fact, it's even more important than calcium. That's because your body needs vitamin D to be able to properly absorb calcium. Without adequate levels of vitamin D, the intestine absorbs only 10 to 15 percent of dietary calcium. Research shows that the bone-protective benefits of vitamin D keep increasing with the dose.
So here is my advice for getting optimal levels of vitamin D:
1. Get tested for 25 OH vitamin D. The current ranges for "normal" are 25 to 137 nmol/L or 10 to 55 ng/ml. These are fine if you want to prevent rickets -- but NOT for optimal health. In that case, the range should be 100 to 160 nmol/L or 40 to 65 ng/ml. In the future, we may raise this "optimal" level even higher. ... Five more important tips and medical references http://www.huffingtonpost.com/dr-mark-hyman/vitamin-d-why-you-are-pro_b_585311.html
