Later On

A blog written for those whose interests more or less match mine.

Important Vitamin D article (and test info)

with 2 comments

Here’s the article, which includes:

“Vitamin D deficiency has become epidemic for all age groups in the United States and Europe”

“The amount of 7-dehydrocholesterol in the epidermis is relatively constant until later in life, when it begins to decline. A person 70 years of age exposed to the same amount of sunlight as a 20-year-old person makes ~25% of the vitamin D3 that the 20-year-old person can make.”

“Melanin evolved as an effective natural sunscreen. Because it efficiently absorbs UVB photons, people with increased skin melanin pigmentation require longer exposures to sunlight to make the same amount of vitamin D3, compared with light-skinned people. For example, a young adult with skin type III (always burns, always tans) who was exposed to 1 minimal erythemal dose (MED) of 54 mJ/cm2 exhibited a 50-fold increase in blood concentrations of vitamin D3 within 8 h, whereas an adult of the same age with skin type V (an African American who never burns and always tans) who was exposed to 54 mJ/cm2 did not exhibit any significant increase in circulating concentrations of vitamin D3. The adult with skin type V required 5-10 times the exposure and exhibited only a 30-fold increase in the blood concentration of vitamin D3, to~30 ng/mL”

“Sunscreens work by absorbing UVB radiation and some UVA (321–400 nm) radiation before it enters the skin. Therefore, it is not surprising that a sunscreen with a sun protection factor (SPF) of 8 reduces the capacity of the skin to produce vitamin D3 by >95% (Figure 4Go) (20); properly used sunscreen with a SPF of 15 reduces the capacity by >98%.”

“Above 37°latitude during the months of November through February, there are marked decreases (~80-100%, depending on latitude) in the number of UVB photons reaching the earth’s surface. Therefore, very little if any vitamin D3 is produced in the skin during the winter.”

“Vitamin D3 is fat soluble and is stored in the body fat. Any excess vitamin D3 that is produced during exposure to sunlight can be stored in the body fat and used during the winter, when little vitamin D3 is produced in the skin. We recently determined that there was 4-400 ng/g vitamin D2 and vitamin D3 in abdominal fat obtained from obese patients undergoing gastric bypass surgery. Therefore, for obese individuals, the fat can be an irreversible sink for vitamin D, increasing the risk of vitamin D deficiency. We observed that, when we gave nonobese and obese subjects a 50,000 IU dose of vitamin D2 orally or exposed them to simulated sunlight in a tanning bed for the same periods of time, the obese subjects exhibited increases in blood vitamin D concentrations of no more than 50%, compared with nonobese individuals.”

So, although the idea that “15 minutes of sunlight will produce all the Vitamin D you need” is attractive, it is also simplistic and, in general, wrong—which is why studies looking at the actual vitamin D in the blood show that vitamin D deficiency is common.

There are two vitamin D tests (link NSFW—starts with sound) — 1,25(OH)D and 25(OH)D. 25(OH)D is the better marker of overall D status. It is this marker that is most strongly associated with overall health. The correct test is 25(OH)D, also called 25-hydroxyvitamin D. The gold standard company is DiaSorin. Quest labs is the largest commercial lab in the US and they use this company to measure 25 hydroxy D levels. However, many other commercial labs don’t.

Healthy people in the tropics and subtropics who receive ample sun exposure have 25-hydroxyvitamin D values of 45-50 ng/ml or 115-128 nmol/l.

Written by Leisureguy

20 December 2006 at 9:34 am

Posted in Health

2 Responses

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  1. Very interesting article. I was recently DX with vitamin D deficency via blood tests. The 1,25 (OH)D was normal but the 25 (OH)D was not normal. It showed up at as 6. (LOW) I am relatively fair skinned and live in hot climate and still deprived of Vitmain D. I am on Calcitriol and have to stand in the sun every day for 15 minutes with no sun screen. The D level was so low that the PTH was over 100, (Very high) I do have symptoms and feel like ^$%$^%!

    Thanks for this most interesting article.

    Lisa

    Like

    Lisa Rose

    27 December 2006 at 7:21 pm

  2. I just was tested at a clinic in New Zealand for Vit D 25 Hydroxy and received a score of 52 nmol/L, which on their charts was considered normal, as anything with a range between 50-150 nmol/L was considered normal. In reading the comments and observations on this site I am not sure I really am in a good normal range. The first problem is converting the British nmol/L to the American standards. Can anyone assist me in converting and analyzing my results in an American context??

    Thanks.

    Like

    Steve Raymen

    28 December 2006 at 2:48 am


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