Maybe "size matters" and maybe not so much. I am only 5'3" and 117 lbs yet I require 8000 iu/day to hold steady at around 50 ng/ml.  So small body needs large dose. I have seen the opposite as well.

I totally agree that the current recommendations are absurd but appropriate dosage for Vitamin D cannot be determined by body size nor any other observable I know of except for blood testing.

Grassrootshealth have recently published new data on responses to vitamin D supplementation.
A 25(OH)D test shows how your body responds to oral supplementation / sun exposure.
Everyone responds individually, most people require more than expected.
Remember in the same way our natural production of the anti-inflammatory anti-oxidant cholecalciferol has been disrupted by current lifestyle changes so to most people fail to get sufficient sleep, so production of the other anti-inflammatory antioxidant, melatonin, is disrupted by light at night and insufficient exposure to bright light during the day.
We make a  very good job of totally wrecking our natural secretion/production of anti-inflammatory anti-oxidant protection.  It's such a shame inflammation and oxidation create dysfunctional mitochondria resulting in metabolic syndrome, diabetes, heart disease cancer and Alzheimer's etc.
Pity we haven't sufficient common sense to go to bed early and spend time outdoors in the midday sunshine.

Vitamin D supplementation does not work in linear manner.  From International Journal of Cancer Research 2011 (pdf link on request by commentators):

Starting at the following vitamin D ng/ml participant levels and adding on increments of 1,000 25(OH)D supplement daily:

10 ng/ml + 1,000 D = 11 ng/ml
30 ng/ml + 1,000 D = 38 ng/ml
50 ng/ml + 1,000 D = 55 ng/ml
90 & above each 1,000 D adds 1.6ng/ml

* and 10,000 IU D daily put no one over 200 ng/ml "toxic" threshold
* and 50,000 IU D daily would be required to surpass 200 ng/ml and be toxic

Geoffrey: I completely agree.  I take 10,000 IU/day and at that I STILL only had 41 ng/ml in February.  My GP, who is, well, of substantially lower mass than I am -- probably to the tune of 100 lbs less, at least -- is in pretty much the same boat regarding dosage and results both.

While I don't disagree... we live in a culture were I'm sure their lawyers are telling them not to change their opinion.

Can we expect these expert associations to change their opinion when they are probably faced with law suits up their ... if they do?

Loved his post.
I have added graphs to IU which should be added for age, skin color, latitude, season, etc.
http://www.vitamindwiki.com/tiki-index.php?page_id=1460

The real deal with IOM's recommendation is that it is simple minded. It's more than conservative; it was doomed from creation. An RDA is a failed way to attempt to convey helpful nutrition information to the American public. Sometimes it takes more than one number to convey something of value, and sometimes oversimplifying a concept does more harm than the good generated by its discovery.

Size in weight, of different adults, is probably less of a factor in the D levels they each get from the same IU D taken as a supplement . The measurement is of our D in fluid concentration (ng/ml), not kg. of our body.

A 13 month baby dose of 600 IU/d
is safe for their blood volume. Adults have more blood volume than infants; the weight difference is a distraction (I think).

Between "average" adults we've
similar amount of blood volume.
Two "average" height adults taking the same dose of vitamin D (like rfrancis describes) are likely starting from a different baseline on ng/ml.

Data I reported was for 5 years tracking +/- 3,400 non-hispanic white adults : age 52 +/- 13 years; weight 74 kg. +/- 17 kg.; height 1.71 mt. +/- 0.10 mt.; latitude N. +/- 40.2*; women = 2090; men = 1312.

For some people who are taking a high dose of D3 and are not getting adequate levels as indicated by 25-hydroxy vitamin D test, 1,25 dihydroxy-vitamin D must be checked as well. They might be hyperconverters.

HI, Henry--

Wow! Nice work.

Anyone wanting to see a graphic representation of some thinking about vitamin D, take a look at the graphics commenter Henry Lahore created:http://www.vitamindwiki.com/tiki-index.php?page_id=1460


Hi, Daniel--

Well said!

One thing I would like to see noted on Vit D levels is the name of the lab that does the test. I believe there are only 2 labs in the US that do the test: Lab Corp and Qwest Labs. The reference ranges are different (Lab Corp 32-100 and Qwest 18-77)

I had my D tested in July of 2008 and was found to be low (15.8 Lab Corp). My doctor gave me the standard script for 50,000 units 1x a week. I knew that D3 was suppose to be superior to the D2 that was prescribed. I decided to go with the D2 for the first 8 weeks, then switch to D3 for the next 8 weeks to compare the results and rate of rise in Vit D levels.

On the D2 my levels went DOWN to 14.9! I was shocked. The nurse pretty much called me a liar and said I hadn't taken the D2. Not only did I take it, I was fanatic about it. I enjoyed the chance to do a small interesting experiment on myself. I then switched to D3 (Carlson Labs brand) for the next 12 weeks at 50,000 units a week. That brought my level up to the low 30s. I quit following the docs advice of 50,000 units per week and increased to 100,000. That got the level up in the 50s. I then read an article by the Iowa bone center in Waterloo, IA that recommended 150,000 units per week. After 4-5 months of that my level was 77. I now take 100,000 per week and am waiting to retest.

I take 10,000 u soft gels by Carlson Labs, and they are small enough to be easy to swallow. I get them at Vita Cost online, current price is $10.93 for 120.

(I am not affiliated in any way with Carlson Labs, their products just work well for me.)

"The Institute of Medicine kept thinking about vitamin D somewhere in the Stone Age"
If they did we would all be better off. You can gauge the optimal evolutionary level of vitamin D by looking at present day hunter gatherers. I don't have time now to find the link but it is in the 40-50 ng/ml range.

"You can gauge the optimal evolutionary level of vitamin D by looking at present day hunter gatherers. I don't have time now to find the link but it is in the 40-50 ng/ml range."

Reference please !

I think you will find that the highest vitamin D levels are found in northern Europe.

Vitamin D production from UV radiation: The effects of total cholesterol and skin pigmentation

RIP Frank Garland

My 71 yo husband's recent test came out surprisingly high at 111! The doctor advised him to stop taking extra vitD. He's been taking 2000IU for at least 2 years and his number was always around 50. Nothing else has changed. He only goes out into the sun maybe once a week for an hour or less.

Are mistakes common in these test results?  

I guess he'll have to retest soon to see.

Para-thyroid hormone rises and  the kidney tubules re-absorb calcium; then inactive 25 D is converted into active 1,25 D. If someone can show me cholesterol controls our para-thyroids I'd like to hear.

Low magnesium in circulation stops para-thyroid up-regulation.
Adequate magnesium is desireable for down the line active 1,25 D production.

I'm 6'2'' and 200 and so far I haven't been able to get my level above 31. I went from 3,000 to 5,000 units and picked up maybe two points. I switched to carlson oil based capsules and bumped it up to 8,000 a day. Wondering if I should push it to 12,000 (caps are 4,000 apiece). I plan on re-testing in August.

Kenneth

"I believe there are only 2 labs in the US that do the test: Lab Corp and Qwest Labs."

Single test:
http://www.zrtlab.com/vitamindcouncil/home-mainmenu-1.html?page=shop.product_details&flypage=flypage.tpl&product_id=4&category_id=1

If you trust the accuracy of blood spot tests for Vit D (and the Vit D Council seems to!)--
4 test kit:
http://www.zrtlab.com/vitamindcouncil/home-mainmenu-1.html?page=shop.product_details&flypage=flypage.tpl&product_id=5&category_id=1

For some, when the level of (inactive) 25 D hits 30 - 40 ng/ml the para-thyroid feedback loop kicks in. The hormone secretion diminishing then causes  a 25 D production down shift.

When the (active) 1,25D is being generated in the kidney tubules it draws down on the pre-cursor 25 D. For some individuals they might see measured blood level of 25 D drop then; if liver synthesis or fat storage slow to respond.

One commentator M.D. here made the point that we want to measure 25 D and not 1,25 D. It seems what's available on demand is more significant than what got activated already.

In November 2010, my vitamin D level was tested with the 25(OH)D, twice. The first result was 12 ng/ml and the second results (a week later) was 7 ng/ml. My doctor prescribed 50,000IU/week. I took that for about 8 weeks and through some more in-depth research which led me to this blog, I discovered the difference between D2 and D3 and, of course, my prescription is Ergocalciferol. At that point, I bought the Kirkland-brand 2,000IU D3 gelcaps and have been taking them (4 per day = 8,000IU or 56,000IU/week) since early- to mid-January. My levels were re-tested again on February 18, 2011 and it is 46 ng/ml.

Is that a quicker-than-normal increase in the 25(OH)D? It seems very quick for the level to rise 34-39 ng/ml. Should I reduce the dosage at this point or maintain it at 8,000IU/day for the next 3 months to see what the level does?

Thanks in advance for any advice or guidance those in the know can provide!

Jeff