Everything You Ever Wanted to Know About Vitamin D from the Expert,
A medical librarian blog  Oct 2009
http://www.happyhealthylonglife.com/happy_healthy_long_life/2009/10/goodbye-sun.html 
 Dr. Michael Holick. How Much Do We Need? Why Is It So Hard to Get Enough? What About Breast-Fed Babies? Why Is It So Important for Good Health?
When it comes to good health, I pay very close attention to how the experts are taking care of themselves.
Dr. Michael Holick, the 62 year old Professor of Medicine, Physiology, and Biophysics at Boston University's Medical Center is probably THE world expert on Vitamin D & health--he's been studying Vitamin D for over 35 years.  When Holick talks--I'm listening!
What's his personal prescription for getting enough of this liquid gold?
    1. 2000 IUs of vitamin D a day.
    2. 3 glasses of milk a day = 300 IUs of Vitamin D
    3. 400 IUs in his daily multivitamin
    4. Between supplements & milk he's getting 2700 IUs a day
    5.  He plays tennis & cycles outside in his free time.  He always wears sunscreen on his face--but leaves his arms & legs exposed--but he lives in Boston.  Sensible sun exposure on your arms & legs is the BEST way to build up your Vitamin D stores--10 minutes a day if you are fair-skinned, between the hours of 10-3, with sunscreen on your face, for 2-3 times a week. That ought to do it!
    6.  What's his 25-hydroxyvitamin D level?  He's consistently in the 50-60 ng/mL range.  Just where you'd want to be to get all the health benefits of D.  30 ng/mL is the minimum and you can go all the way up to 100 & still be on the very safe side.
So, why am I writing about Vitamin D again?  There's just so much to say about it!  And besides, it's closing in on November--which means if you live north of Atlanta, Georgia there is no way you can get any vitamin D from the sun.  It's too high in the sky & the angle is too oblique.  By the end of the winter--if you aren't taking a Vitamin D supplement you are going to be deficient!  Not a good thing.
You can stand stark-naked on top of a building in Boston all day in February and get zippo Vitamin D!  So take that supplement & get some Real Sun in the summer!
Why Should I Care If I'm Sufficient or Deficient in Vitamin D?
I know, it sounds like snake-oil.  How can Vitamin D possibly have an effect on so many chronic diseases and conditions?
Simple--every cell and tissue in the body has a Vitamin D receptor--and all of them depend upon D for optimal health.  Here's just a sampling of the bad things that can happen if you aren't getting enough.
    * Cardiovascular disease - increase risk of heart attack 142% if under 15 ng/mL
    * Cancer - if you live in a northern latitude you have a higher risk of colorectal, breast, & prostate cancers.  Projected 50% risk reduction with over 1000 IUs a day.  Adequate Vitamin D actually inhibits cancer cell growth.
    * Autoimmune Diseases
    * Osteoporosis/fractures - study after study shows the necessity of Vitamin D to absorb calcium & build strong bones.  With sufficient Vitamin D you'll absorb 30% of the calcium in your diet.  Without Vitamin D, the absorption rate drops to 10-15%.  Although Dr. Holick recommends a Vitamin D level of 50 as the optimal number to prevent osteoporosis,  Dr. Heike A. Bischoff-Ferrari concluded that the optimal level of vitamin D to prevent hip and nonvertebral fractures in older adults should be at 75 nmol/l.  ("Optimal serum 25-hydroxyvitamin D levels for multiple health outcomes" in Sunlight, Vitamin D and Skin Cancer, edited by Jorg Reichrath, 2008)
    * Respiratory infections & flu - Yes, believe it!  Your immune system hums with D. Cytokine & immunoglobulin production is regulated by Vitamin D.  2009 Archives of Internal Medicine article shows the higher the Vitamin D, the lower the risk of upper respiratory tract infections.
    * Osteomalacia - generalized & isolated bone pain - it can vanish with adequate Vitamin D
    * Arthritis - both rheumatoid & osteoarthritis
    * Multiple sclerosis -risk increases the further one gets from the equator.  Studies show the risk is reduced for outdoor workers, and in people with higher levels of Vitamin D.
    * Schizophrenia - risk diminished in infants supplemented with D in first year of life.
    * Type 1 Diabetes - Finnish study showed an 80% reduction in developing Type 1 diabetes for infants receiving adequate Vitamin D supplementation.
    * Dementia - both vascular and Alzheimer's
    * Fibromyalgia is often a misdiagnosed Vitamin D deficiency causing generalized muscle aches & pains.
    * Type 2 diabetes.  May exacerbate type 2 diabetes & impair insulin production.  Obesity, associated with type 2 diabetes,  prevents adequate Vitamin D absorption.
Why Are So Many of Us Vitamin D Deficient & What Gets in the Way of Absorbing Adequate Vitamin D?
    * We're Indoors & Wear Sunscreen. We spend most of our time indoors & when we're outside we're slathered in sunscreen, or mostly covered up with clothes.  Dermatologists have been telling us to wear sunscreen & avoid the sun for almost 40 years.  An SPF 15 reduces Vitamin D absorption by 95-99%
    * No Mid-day Sun. To get adequate Vitamin D from the sun you would have to be exposed to the sun in the peak hours of 10 am to 3 pm.
    * It's a Vitamin D Deficiency Epidemic!  Vitamin D deficiency (a level under 30 ng/mL) is epidemic  in adults over 50 (over 70% of us); 50% of children are deficient; 42% of young adults are deficient; and Vitamin D deficiency even exists in California, Florida, Arizona, and Saudi Arabia.  Personally, I don't know a single friend who wasn't deficient when they were first tested.
    * It's an Age Thing. Age decreases the ability of the skin to make Vitamin D.  A 20 year old makes 3 times more Vitamin D than a 70 year old.
    * Dark Skin Color.  African-Americans need to be out in the sun 5-10 times longer to get enough Vitamin D.  They are walking around with a natural SPF of 15.  Many researchers believe that the excessively low levels of D in African Americans may be responsible for their higher rates of prostate cancer, hypertension, and diabetes.  For an interesting story of skin color & Vitamin D click here 
    * Obesity.  The more you weigh, the less Vitamin D is getting into your blood stream.  Obese people can only utilize 50% of their Vitamin D--because it ends up in their body fat & can't get into their blood stream.  They need to get 2-3 times as much Vitamin D from the sun or supplements to bring their levels up to normal.
    * Kidney disease & Liver Damage.  Either one will impair the body's ability to activate circulating Vitamin D.
    * Certain Drugs Inhibit Absorption of Vitamin D.  Like anticonvulsants, bile acid sequestrants (for cholesterol), Tagamet, corticosteroids, and heparin.
How Do I Find Out What My Level of Vitamin D Is?
    * Ask your doctor to order a simple, low cost 25-hydroxyvitamin D test for you.  It's the only way to know what your baseline is.  Then follow-up a few months later if you are deficient.
    * For optimal health aim for Dr. Holick's goal of 50 ng/mL.  Absolutely get yourself up to 30 ng/mL.  You're safe up to 100 ng/ML.  And it's impossible to get too much Vitamin D from the sun--the body will regulate it.  With supplements you would have to take over 10,000 IUs/a day, for six months to have Vitamin D intoxication.  Lifeguards wearing no sunscreen have been tested--they have super-high levels, and no intoxication.
    * Every 100 IUs of Vitamin D you take, you can figure it will raise your Vitamin D level by 1 point, assuming you are not obese--which necessitates increasing the level by 50% or more.
    * For those who are very low in Vitamin D, under physician guidance, you may need to take 50,000 IUs of Vitamin D2  (yes, D2--is now confirmed to be just as good as D3) once a week for 8 weeks, then 50,000 IUs every 2 weeks "forever" after, according to Holick.
How Much Vitamin D Can I Get Naturally From the Sun?  What's Safe?
    * You can get your Vitamin D from the sun, from April-September if you live north of Atlanta, Georgia, and it is the best source of Vitamin D.
    * If you are sunbathing mid-day on Cape Cod in the summer, wearing a bathing suit, without sunscreen, and you have fair skin, you will get 10,000-20,000 IUs of Vitamin D in just 15 minutes of exposure. Do that 2-3 times a week and you'll build up a healthy storehouse.
    * The body is able to store the Vitamin D it gets from the sun far longer than it can store the Vitamin D it gets from supplements.
    * Mother Nature has designed the body to store the Vitamin D we get from the sun in our body fat, and release it when we aren't "making" any more.
    * Our Vitamin D levels peak in the summer--but in you are barely Vitamin D sufficient at the end of the summer (a level of 30 ng/mL) you will deplete those stores in one month.  By the end of the winter, you will be severely Vitamin D deficient, unless you are taking a supplement.
    * Sensible sun exposure.  Here's what Dr. Holick advocates.  10-15 minutes of exposure on arms & legs in the peak sun hours of 10 am - 3 pm, two or three times a week.  Use a sunscreen on your face, and after 10-15 minutes get out of the sun or slather up.   Overexposure can increase non-melanoma skin cancer.   10-15 minutes is not overexposure. 
    * To get exact guidance on how long you would need to stay in the sun to get enough Vitamin D, based on where you live, your skin type, the time of day, & the time of year--take a look at Dr. Holick's book, The UV Advantage, or try Dr. James Dowd's online sun exposure calculator.
    * Vitamin D from the sun & depression.  Although Vitamin D is known to lessen depression and boost the mood--unfortunately, only the natural kind from the sun has this effect.
What About Skin Cancer?  I Thought It Was Risky to Be Out in the Sun Without Sunscreen?
    * The American Academy of Dermatologists is still not recommending that we go out in the sun without sunscreen for any amount of time. They are recommending we take supplements and eat fish.  But remember, Dr. Holick is only recommending short sun exposure with the face protected by sunscreen, and the truth of it is--melanoma, the most dangerous of skin cancers, is usually found in the unexposed parts of the body that never see sunlight.
    * Interestingly, occupational sun exposure decreases the risk of malignant melanoma and lifetime sun exposure is associated with a lower risk for malignant melanoma.
    * The Dermatological & Cancer Societies of Australia have recently changed their position on sun exposure.  Now that studies have shown that 30-50% of Australian's are Vitamin D deficient because the sunscreen campaigns have been so successful, the Aussies are rethinking "their sunscreen message".  Their new message:  Get sensible sun exposure.  Enough to get adequate Vitamin D, not too much to increase cancer.
Any Special Recommendations for Pregnant Women & Infants?
    * Vitamin-D deficient infants will never attain their genetically preprogrammed bone density or height.  That's one scary thought!
    * A Boston study looked at 40 mother-infant pairs--the moms took the recommended 400 IU/day Vitamin D in their prenatal vitamin and drank 2.3 glasses of milk a day--at birth, 76% of moms were Vitamin D deficient--81% of newborns were deficient.
    * All pregnant women need get 1000 IUs a day in addition to the Vitamin D in their prenatal vitamin, and an additional 200 IUs from their diet, according to Holick.
    * Higher Vitamin D levels decreased the likelihood of preeclampsia, and reduced the need for C-sections.
    * Moms who got adequate Vitamin D during pregnancy reduced the risk of wheezing disorders in their children by 61%.
    * Breast-feeding moms need to be vigilant that their babies are getting enough Vitamin D.  The breast milk of moms who are not getting enough Vitamin D has a paltry 25 IUs of Vitamin D per liter (1 quart, 2 ounces).  Not even close to the 400 IUs their babies need.  It would take 4000-6400 IUs/a day for a breast-feeding mom to get enough Vitamin D into her breast milk to meet the baby's requirement of 400 IUs a day.  But according to Holick, until more studies are done, "it's not something we're recommending."  Hopefully, we'll be able to in the near future."  In the meantime--breast-feeding moms need to make sure their babies are getting 400 IUs/a day of a Vitamin D supplement.
What Kind of Supplementation Does Dr. Holick Recommend?
    * 1000-1500 IUs/a day for most children
    * 1500-2000 IUs/a day for adults
    * All pregnant women need get 1000 IUs a day in addition to the Vitamin D in their prenatal vitamin, and an additional 200 IUs from their diet.
    * The American Academy of Pediatrics now recommends 400 IUs/a day for infants.
    * In August 2009 Dr. Holick participated in an Expert Panel convened by the Institute of Medicine to work on new recommendations for Vitamin D--in light of all the research that has come out recently.  Expect new standards sometime around the Spring of 2010.
Can You Get Enough Vitamin D from Diet Alone?  Not Likely!
    * The only food that contains Vitamin D, is oily fish, like wild (not farmed) salmon--clocking in at 500-1000 IU a serving.  See a Boston University breakdown of Vitamin D for various fish here.
    * Cod Liver Oil is an OK source.
    * Some foods are fortified, but at a typical 100 IUs a serving that's about 10 glasses of milk a day.
Want to learn more?   {Links}
Listen to Dr. Holick and Dr. James Dowd on the People's Pharmacy
The American Academy of Pediatrics updated Vitamin D guidelines for infants & children
The Audio-Digest Family Practice Summary of "Vitamin D: the Vital Vitamin".  57(12): Mar. 28, 2009
NPR Transcript from the Living on Earth broadcast of "Skin Color and Vitamin D"
Why Is Vitamin D My Favorite Vitamin?  Let Me Count the Reasons
"Institute of Medicine Studies a Boost In Vitamin D".  AMA News April 20, 2009  
Gretchen Reynolds.  Phys Ed. Can Vitamin D Improve Your Athletic Performance?  New York Times Sept. 23, 2009
So, What About Me?
I try hard, but rarely succeed in taking 2000 IUs of D a day, plus about 400 IUs from Citracal calcium supplements, and maybe an additional 400 IUs from an occasional multivitamin or from fortified food.  I'm not often out in the mid-day sun--but when I am, don't tell anyone--I'm not wearing sunscreen.
I haven't been retested in over 2 years, when it was 33 ng/mL at the end of winter.  I plan to retest in January 2010.