http://www.findarticles.com/p/artic...30/ai_111356934
Soaking up the D's - vitamin D
Michael F. Holick
It's winter. Do you know what your vitamin D level is?
Millions of adults are at risk of vitamin D deficiency, according to Michael Holick, director of the Vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center.
Many people use too much sunblock to make enough vitamin D, says Holick. Multivitamins supply only about half of what people need. And only a few foods are good sources.
The consequences: Vitamin D deficiency can exacerbate osteoporosis. And it can cause weak or aching muscles and bone pain that's often misdiagnosed as arthritis or fibromyalgia. To make matters worse, many doctors miss a vitamin D deficiency because they order the wrong blood test.
Q: Why do so many people get too little vitamin D?
A: Very few foods contain it, and most people get too little sun to make it. Your skin can make vitamin D when it's exposed to sunlight. When the highest energy ultraviolet light, called UVB, penetrates the skin, it converts a precursor into vitamin D, which becomes 25-hydroxyvitamin D in the liver, and is then activated to 1,25-dihydroxyvitamin D in the kidneys.
But if you live north of Los Angeles on the West Coast or Atlanta in the East, you don't get enough UVB from the sun in the winter to make adequate vitamin D (see "The Winter Sun," p. 5).
And even in the summer, many people are so concerned about getting too much sun that they always use sun protection, which blocks the UV light that makes vitamin D in your skin. The message used to be "don't burn" and "get some safe sun," which I totally agree with. But now the recommendation is to get no direct sun exposure. That has put many more people at high risk of vitamin D deficiency.
Q: What harm does vitamin D deficiency do?
A: It increases the risk of bone fracture. Vitamin D increases the efficiency of your intestine to absorb calcium and phosphorus from food, so you can mineralize your skeleton. It also increases the activity of bone cells that make and lay down bone matrix.
Q: The matrix is like the frame of a building?
A: Yes. If you have an adequate amount of calcium and phosphorus, it gets incorporated into the bone matrix and you have good, healthy bone. Young children who are deficient in calcium and vitamin D are unable to properly mineralize the rubbery matrix. Gravity pushes on the skeleton and causes the typical bowing of the legs that you see in a child with rickets.
By the time you're an adult, your long bones have stopped growing and you have enough calcium in your bones to prevent skeletal deformities. Instead, if an adult is deficient in vitamin D and not getting enough calcium, calcium is drawn out from the bones, which causes osteoporosis.
Q: The bones break down?
A: Yes. Bone cells called osteoclasts dissolve the matrix and release the calcium out of the bones and into the bloodstream. So a vitamin D deficiency will precipitate and exacerbate osteoporosis because it's increasing the number of holes in your bones.
In addition, bone cells called osteoblasts continue to produce new matrix, just like they do in children. However, when you are deficient in vitamin D, the matrix cannot be properly mineralized. The result is osteomalacia, the bone disease that's caused by vitamin D deficiency.
Q: How does osteomalacia differ from osteoporosis?
A: Osteoporosis isn't painful unless you have an acute fracture. Holes in your bones don't hurt.
In contrast, osteomalacia can cause muscle weakness as well as bone ache and bone pain. Until you have it, you can't really appreciate this gnawing sensation. Many patients are diagnosed with some kind of arthritis or collagen-vascular disease or fibromyalgia. In my clinic, I find that patients with aching bones are often suffering from vitamin D deficiency.
Q: Why does the body take calcium from the bones?
A: We evolved from the ocean, which is a high-calcium bath. Early in evolution, calcium became critically important for most metabolic functions--for example, to keep your heart beating and your muscles contracting. So the body makes sure that your blood calcium is in the normal range, even if it means removing calcium from your bones.
Q: Do people who get more vitamin D have stronger bones?
A: Yes. For example, postmenopausal women in Boston who were given 700 International Units of vitamin D a day for two years lost less bone than women who got 100 IU a day in addition to the 100 IU from their usual diets. All the women also received 500 milligrams of calcium a day.
Q: Does vitamin D reduce fracture rates?
A: Absolutely. For example, in 1992, French researchers showed that by giving nursing home residents 800 IU of vitamin D and 800 mg of calcium a day, they could markedly reduce the risk of fractures. Multiple studies done in the U.S. show the same in men and women.
Q: Why give both vitamin D and calcium?
A: You need the vitamin D to increase the efficiency of calcium absorption. If you're deficient in vitamin D, you only absorb about 10 to 15 percent of the calcium you consume. So if you just take calcium it may not do you any good.
Every day you lose about 100 to 200 milligrams of calcium in your urine and about 100 to 200 mg from the gastrointestinal tract. So if you had 1,000 mg of calcium in your diet and you absorb 15 percent, that's 150 mg. But if you've lost 100 mg in urine and 100 mg from the gastrointestinal tract, you have a 50-milligram deficit.
Where does that come from? It's not like the federal government, which can just forget about the deficit. Your body takes those 50 milligrams out of your skeleton to make sure your blood calcium remains normal.
Q: Are women at greater risk of osteomalacia?
A: No. But women start out with lower bone density so they begin to fracture earlier in life due to both osteoporosis and vitamin D deficiency.
BEYOND BONES
Q: Could vitamin D deficiency cause other problems?
A: It may raise the risk of Type 1 diabetes, multiple sclerosis, congestive heart failure, and some cancers.
We also have preliminary evidence that vitamin D may lower blood pressure. When we exposed vitamin-D-deficient people with mild hypertension to just enough UVB light to raise their blood levels of vitamin D to normal, their blood pressures became normal. We were able to maintain them at a normal blood pressure for nine months by continuing that therapy. But the results need to be confirmed.
Q: How might vitamin D affect blood pressure?
A: If your kidneys produce more of a hormone called renin, you have a higher risk of hypertension. And the active form of vitamin D--1,25-dihydroxyvitamin D--decreases renin production.
Q: What's the evidence on vitamin D and diabetes?
A: It's intriguing. The NOD mouse, which is used to study diabetes, gets Type 1 diabetes when it's about 200 days old. If you treat the mice with activated vitamin D throughout their lives, it reduces their chances of getting diabetes by 80 percent. And a study in Finland where--vitamin D deficiency is common--followed 10,000 children for 30 years. Those who took at least 2,000 IU of vitamin D a day during the first year of life had an 80 percent lower risk of diabetes than those who took no vitamin D.
Q: How is vitamin D linked to multiple sclerosis?
A: In MS, the body's antibodies attack the myelin sheath that covers nerves. To study the disease, researchers inject myelin into mice. The mice develop antibodies to it and the antibodies start destroying myelin on the animals' nerves. That doesn't happen if the animals get activated vitamin D first.
Q: Any evidence in people?
A: So far, it's just circumstantial. For example, we know that the further you live from the equator, the higher your risk of multiple sclerosis.
Q: What's the link between vitamin D and cancer?
A: We know that almost every tissue in your body--brain, breast, bone, colon, intestine, heart, kidneys, and prostate--has a receptor for the active form of vitamin D. The question is: why?
It turns out that the active form of vitamin D is one of the most potent hormones to inhibit cell proliferation. So if you have a cancer cell that's proliferating out of control, activated vitamin D could inhibit its growth. That's what happens when activated vitamin D is added to breast, colon, lung, or prostate cancer cells.
Q: In test tubes?
A: Yes. And researchers are getting excited about using vitamin D-like compounds called analogs to treat cancer. The analogs are designed to suppress proliferation more--and raise calcium levels less--than activated vitamin D. The problem is that the cells can become resistant.
Q: Are there any human studies?
A: Researchers are investigating a vitamin D analog on liver cancer--hepatoma. The preliminary data look spectacular. Liver cancer isn't a big problem in the U.S. But it's a major problem in Asia, because many Asians have hepatitis C, a viral infection that markedly increases their risk of developing hepatoma later in life.
Q: What about other cancers?
A: The results haven't been as good. Early studies showed that leukemia patients who were given activated vitamin D went into remission, but then they all died. Researchers think that some of the cells became resistant and more aggressive in their growth. But a recent study found that giving a vitamin D analog with chemotherapy may be effective in treating prostate cancer, so that's another possibility.
SUN SHY
Q: So sunscreens can be a problem?
A: Yes. If you use a sunscreen rated SPF 8 properly, it reduces your ability to make vitamin D by more than 90 percent. The same happens it you use an SPF 15 improperly--if you use too little or don't reapply it every two hours. And that's a shame, because there are clear benefits to sensible exposure to sunlight, and essentially no evidence that it will increase your risk of skin cancer.
Q: What's sensible?
A: If the sun's UVB rays are reaching you, we're talking about no more than maybe five to ten minutes of sun exposure on the arms and legs or face and arms two to three times a week. I recommend going out sometime between the hours of 11 a.m. and 2 p.m., because that's when your skin makes the most vitamin D. You could make vitamin D at 10 a.m., but then you'd have to be out for a longer period of time. In Boston, you wouldn't make any vitamin D at 8 a.m., even if it's a sunny summer day.
Q: Because the sun's UVB rays aren't reaching you?
A: Yes. Just like in the wintertime, the UV rays come in at an angle. That means that the rays--or photons--have to pass through more ozone in the atmosphere, and UVB rays are efficiently absorbed by ozone. Even if the sun is directly above you at noontime at the equator, only one tenth of one percent of the UVB photons, which are responsible for making vitamin D, actually penetrate to the earth's surface. So if the sun comes in at an angle, essentially none of those photons reach the Earth.
Q: You'd need less time in Florida than Boston?
A: Yes. Five to ten minutes is for a light-skinned Caucasian in Boston in June between 11 a.m. and 2 p.m. In Florida, it may be only two to three minutes.
Q: And Floridians can make vitamin D year-round?
A: Yes, even as far north as Los Angeles or Atlanta. But you may need to stay out a little longer because the sun isn't as strong. North of that latitude--above 35 degrees--you can't make any vitamin D in your skin in the winter, even at noon. In fact, Canadians can't make vitamin D in their skin for four to seven months of the year. They're at high risk of vitamin D deficiency.
Q: Why not get vitamin D from foods?
A: It's not easy. Many experts now agree that, on average, you need 1,000 IU a day if you're not exposed to sunlight. Only a few foods contain vitamin D (see "Getting Your D's"). And a typical multivitamin-mineral supplement has only 400 IU.
Q: Why did the National Academy of Sciences recommend only 400 IU for people over 50 and 600 IU for people over 70?
A: I was on the committee that issued the recommendations. Many committee members believed that the levels were inadequate, but we were obligated to base our recommendations on published studies. We had evidence that much higher levels were needed, but it hadn't yet been published.
For example, in the study we just published, we gave healthy young and middle-aged adults 1,000 units of vitamin D a day at the end of the winter and the beginning of the spring. That raised and maintained their blood levels of 25-hydroxyvitamin D right where you want them--between 30 and 40 nanograms per milliliter. In the absence of sun, that's what you need to maintain a healthy vitamin D status all year round.
Q: What level is deficient?
A: A 25-hydroxyvitamin 13 below 20 nanograms per milliliter. From 20 to 30 is borderline adequate. A healthy level is between 30 and 50.
Q: Do older people absorb less vitamin D?
A: Aging has no impact on how much vitamin D you absorb from food or pills. How much you make from the sun is a different story. If you're 70, your skin can make only a quarter of the vitamin D that a 20-year-old can make when exposed to the same amount of sun (see "More Years, Less D"). But a 70-year-old can make enough.
Studies have shown that if elders are out in the sun light for 15 to 20 minutes a couple times a week, they'll maintain their vitamin D levels. In Britain, researchers showed that if you put a UVB light source in the ceiling in a nursing home, you can maintain adequate vitamin D levels in residents.
TOXIC LEVELS
Q: Why is milk fortified with only 100 IU of vitamin D per cup?
A: Because of the risk of toxicity.That's been the limit since the 1930's, even though it takes huge amounts to cause toxicity. We got a call from a doctor in Florida whose patient bought a powdered vitamin D supplement from a company in Canada. The patient started taking two teaspoons a day, which was supposed to have 2,000 IU.
But the company forgot to dilute the powder, so the patient was actually ingesting up to a million units a day. And he ended up with vitamin D toxicity. But most experts agree that even if you take 5,000 to 10,000 IU a day, you won't get vitamin D toxicity.
Q: Why did the National Academy say that people shouldn't exceed 2,000 IU a day?
A: Our committee recommended an upper safe limit of 2,000 IU because we had to rely only on published studies. Other studies suggest that at least 5,000 IU and maybe 10,000 IU a day is safe. It's virtually impossible to get that much from diet and supplements. And there's never been a reported case of vitamin D toxicity because of too much sun. Nature has cleverly programmed into the system that any excess from the sun is destroyed.
Q: What happens if you consume too much vitamin D from food or pills?
A: You absorb too much calcium, so you can get high blood calcium, kidney stones, kidney calcification, kidney failure, soft-tissue calcification, and calcification of your blood vessels that can ultimately lead to death. But you're talking about huge amounts. Remember the Florida patient who was taking a million units a day? Once he stopped taking the vitamin D, his levels fell gradually over three years and now he's perfectly fine.
Q: So you have to take high levels for a long time?
A: Exactly. Typically, I'll give my patients who are deficient in vitamin D 50,000 IU once a week for eight weeks to fill up their vitamin D tank because it's on empty. That works extremely well. Then I put them on 50,000 units once or twice a month. And I've never seen any toxicity.
TESTING
Q: Should people get their vitamin D levels checked?
A: Yes, just like you get your cholesterol checked at least once a year. The best time is around November, because if you're deficient then, you'll be severely deficient at the end of winter. And make sure that your doctor orders a test for 25-hydroxyvitamin D, not 1,25-dihydroxyvitamin D, which is the active form. That can be misleading.
Q: How?
A: Your 1,25-dihydroxyvitamin D levels are a thousand-fold less than your 25-hydroxyvitamin D levels. As you become deficient, the body tries to compensate by increasing the kidneys' production of 1,25-dihydroxyvitamin D. So those levels are normal or even elevated. In 50 percent of all assays done worldwide, doctors order a 1,25-dihydroxyvitamin D assay. I don't have a clue what they do with that information.
Q: They may misinterpret it?
A: Yes. It comes back normal or high, so they think the patient has more than enough vitamin D, when it's really a sign that the patient is becoming deficient.
Q: Do you recommend taking a supplement?
A: Yes. If you get enough sun in the summer and fall, it will carry you through the winter, because you store vitamin D in your body fat. But most people don't get enough.
To give you an example, my mother recently went into a nursing home. While she lived at home, I made sure she wasn't deficient by prescribing 50,000 IU of vitamin D twice a month. I urged her primary care doctor to make sure she didn't become deficient. He finally tested her blood level and she was severely deficient. He's now treating her, as I would, with 50,000 IU of vitamin D once a week for eight weeks followed by 50,000 IU twice a month.
Dhea
cause it might screw up something thats not there. 
so i really dont know what to do anymore i am so confused even with the thousands of question ive asked my doc and i know shes a good geno cause shes sure is on the ball this woman and wont let anything go pass her. 
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