Tuesday, March 20, 2012

What's The Big Deal About Vitamin D? It turns out quite a bit.


Vitamin D deficiency has become a hot topic with headlines about its dangers becoming ubiquitous.  Of course, not everyone agrees on what the problem is and how to best treat it.  
Accordingly, I’ve compiled a list of questions and answers to help people navigate through the plethora of issues raised. If you have additional questions, please send me an email at steven.charlap.md@mdprevent.net.

1.      Can sun exposure restore vitamin D to adequate levels?
It is well documented that lack of exposure to sunlight is a major risk factor for vitamin D deficiency. Therefore, you would think if you increased your exposure to sun, you would be all set. That may not be the case according to one doctor.
Here is an excerpt from Medscape News article from today:
"The 'epidemic' in vitamin D deficiency is clearly not from too little sun exposure," and dermatologists can be confident in insisting that their patients continue their sun protection efforts, said Richard Gallo, MD, PhD, here at the American Academy of Dermatology (AAD) 70th Annual Meeting.
"Clearly solar exposure is an influence — there is no doubt about that — but you cannot predictably say that a certain amount of exposure will normalize vitamin D deficiency," said Dr. Gallo, chief of dermatology and professor of medicine and pediatrics at the University of California, San Diego.
I’m not sure that all doctors agree with Dr. Gallo and I still believe that some sun exposure, up to 15 minutes per day (avoid mid-day peak sun) is prudent unless you have already had skin cancer. By the way, your belly skin absorbs sun the best.

2.      What level of Vitamin D defines deficiency?
Serum 25(OH)D - The circulating half-life of 25(OH)D is 2 weeks. This is the best test to determine vitamin D status. A 25(OH)D level of less than 32 ng/mL is considered vitamin D insufficient. A 25(OH)D level of less than 15 or 20 ng/mL have been used to define vitamin D deficiency. Intestinal calcium absorption is optimized at levels above 32 ng/mL. An Institute of Medicine report recommends that patients should have serum vitamin D levels above 20 ng/mL, but the American Endocrine Society sets this level at 30 ng/mL

One issue I have not seen addressed is the fact that Vitamin D is a fat soluble vitamin and blood teats only detect circulating Vitamin D and not fat-stored Vitamin D. I'm not sure if this is significant in diagnosing deficiency, but I would love to hear if you know of anyone who studied this issue.

3.      Who should be tested for Vitamin D deficiency
It is generally recommended to screen only those individuals who are at high risk for vitamin D deficiency, including patients with osteoporosis, malabsorption syndromes, black and hispanic individuals, obese individuals (BMI >30 kg/m2), and those with several other medical conditions.
I don’t agree with these recommendations as I have found deficiency among a much broader group of patients. I don’t believe we should test everyone, but I do believe in testing everyone over the age of 65 who routinely avoids sun exposure.

4.      Is testing of parathyroid hormone (PTH) necessary to make the diagnosis of Vitamin D deficiency?
No, but it is helpful. An elevated PTH is supportive of the diagnosis.

5.      What is the recommended daily intake of Vitamin D?
There is some debate on this one. Some say for adults it is 800 IU, others 1,000 IU, and still others, even higher. I unscientifically vote for 1,000 in absence of deficiency and initial 2000 to restore levels. Others supplement at much higher dosages, even to 50,000 IUs. 

6.      Is Vitamin D toxic at higher levels?
At blood levels of 125 ng/ML, Vitamin D may be toxic and that is why I believe in treating deficiency more cautiously so to avoid going from one unhealthy extreme to another. Doses can always be increased as needed. Obviously, the greater the deficiency, the higher the restorative dose should be.
7.      Which form of Vitamin D--D2 or D3--is best to treat deficiency?
Most scientists agree that D3 (cholecalciferol) is much better but studies support D2 (ergocalciferol) as well. Stick with D3 which everyone accepts.

8.      Is milk a good source of Vitamin D?
Milk may be an unreliable source.  Fortified milk may contain less than the stated amount of vitamin D3 on the product (in some cases less than 80% of the amount), so if the only reason you are drinking milk is for Vitamin D, drink Almond Milk instead which is also fortified.

9.      What foods are good sources of Vitamin D?
Most dietary sources of vitamin D do not contain sufficient amounts of vitamin D to satisfy daily requirements. Foods thought to contain high amounts of vitamin D3 are oily fish, such as salmon and mackerel. A single serving (3.5 oz) of wild-caught salmon has 988 ± 524 IU vitamin D3, an amount that remains unchanged after baking but that decreases by 50% if the salmon is fried in vegetable oil. In comparison, farm-raised salmon has only 25% the content of vitamin D3 found in the flesh of wild salmon, whereas blue fish and mackerel have even lower vitamin D3 levels, at 280 ± 68 and 24 IU, respectively. Vegetables and fruits are not a good source for vitamin D.
The following foods contain the indicated amounts of vitamin D, as reported by the US Department of Agriculture's (USDA's) Nutrient Data Laboratory
·         Fortified milk (8 oz) - 100 IU
·         Fortified orange juice (8 oz)  100 IU
·         Fortified cereal (1 serving) - 40-80 IU
·         Pickled herring (100 g) - 680 IU
·         Canned salmon with bones (100 g) - 624 IU
·         Mackerel (100 g) - 360 IU
·         Canned sardines (100 g) - 272 IU
·         Codfish (100 g) - 44 IU
·         Swiss cheese (100 g) - 44 IU
·         Raw shiitake mushrooms (100 g) - 76 IU
·         Most multivitamins (1 tab) - 400 IU

10.  Does Vitamin D deficiency lead to cancer, both types of diabetes, and increased mortality (death)?
Recent studies suggest that it does, but further study is necessary. Best to stay at healthy blood level regardless of future study results.

11.  Are there prescription drugs that lead to Vitamin D deficiency?
Drugs such as Dilantin, phenobarbital, and rifampin can induce hepatic p450 enzymes to accelerate the catabolism of vitamin D.

12.  Does Celiac Sprue increase risk for Vitamin D deficiency?
Yes, due to malabsorption.

13.  Who is at greatest risk of Vitamin D deficiency?
Elderly homebound and institutionalized individuals don’t get much sun exposure. However, a study from Boston determined that nearly two thirds of healthy, young adults in Boston were vitamin D insufficient at the end of winter. People with dark skin and older people are also at increased risk because their skin does not absorb sunlight as well as others.

14.  Are there any physical findings for Vitamin D deficiency?
Other than rickets and osteoporosis in extreme cases, in adults with a severe vitamin D deficiency, a physical examination can reveal periosteal (outer surface of bone) bone pain. This is best detected using firm pressure on the sternal (chest) bone or tibia (larger leg bone).

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