OnTrack Reading

Over time I will add to this list of questions that people first encountering the vitamin D3 discussion are likely to want addressed. Many of the answers can also be found on the website VitaminDCouncil.org maintained by Dr. Cannell. My answers will be brief and will include a link to more in-depth answers at Dr. Cannell’s website.

Is Vitamin D3 different than Vitamin D?

Dr. Cannell explains that the naming of various components of the Vitamin D complex are not exactly rational. Here is a brief description:

Vitamin D3 is cholecalciferol (coal’-i-kal-si’-fer-ul) and is either manufactured by the skin from sunlight (or the right tanning lamp) or provided as a supplement or, modestly, by diet.

Cholecalciferol is used by the body to manufacture a pre-hormone called Calcidiol (cal-si-die’-ol) that is then stored for use by various organs in the body. This is the substance that you want to obtain a measurement of when you order a Vitamin D3 test. The proper test is called 25(OH)D and measures the blood level of Calcidiol, not Calcitriol.

Calcitriol (cal-si’-tree-ol) is a hormone manufactured from Calcidiol body stores. It is measured by a test called 1,25(OH)D. The reason this test is not meaningful for our purposes is that the kidneys will first use as much calcidiol from the body stores as is necessary to get calcitriol levels in the blood raised to a level sufficient to maintain proper cell functioning. After, and only after, the kidney has manufactured sufficient blood-level calcitriol will the remaining calcidiol body stores be used by other organs in the body. If one is deficient in calcidiol, the blood level of calcitriol might still be within normal ranges, as it is produced first because sufficient blood levels of calcitriol are necessary to maintain blood calcium levels and calcium is absolutely essential to proper cell functioning.

Now take a look at Dr. Cannell’s explanation of the Vitamin D components on his website.

What is the blood test for Vitamin D3 called?

As explained above and on the Vitamin D3 and Dyslexia page of my website, you want the 25(OH)D test to measure the calcidiol level. The blood test designated 1,25(OH)D will not tell you what the body stores of calcidiol are, but it is the test normally ordered when you ask your physician for a Vitamin D test.

What are the recommended levels by the government?

As I wrote on the Vitamin D3 and Dyslexia page, the AAP recently went back up to 400 IU’s for children. In 1997 the Food and Nutrition Board and the Institute of Medicine (FNB/IOM), responsible for setting dietary intake recommendations, declined to establish a Recommended Daily Amount (RDA) but instead declared that a daily Adequate Intake (AI) of Vitamin D would be 200 IU for infants to 50 year olds, 400 IU for 51-70 year olds and 600 IU for those 71 and older. At that time they also declared a tolerable Upper Limit (UL) , a presumably safe upper limit for intake of Vitamin D, to be 1000 IU for children under one year old and 2000 IU for all other children and adults.

What levels are others recommending?

Levels as high as 4,000 to 6,000 IU’s daily are being advocated for adults who get very little sun exposure. For comparision, multi-vitamins typically provide 200-400 IU’s. However, the amount of Cholecalciferol required to provide 4,000 to 6,000 IU’s is so miniscule (measured in micrograms) that one needs to take care that overdosing is not an issue. There are apparently cases of manufacturing errors resulting in supplements containing levels much higher than the amounts indicated on the label. This is another reason why supplementation should be monitored by blood tests of the calcidiol levels.

The medical community becomes concerned when calcidiol (Vitamin D3) levels fall below about 10 nanograms per milliliter (10 ng/ml) and really doesn’t get concerned if levels are in the high 20’s. (Below a level of 10 ng/ml a child is likely to start to show symptoms of rickets.) Dr. Cannell and others maintain that the body doesn’t begin to store enough calcidiol for use by organs other than the kidney (to maintain essential blood calcium levels, remember?) until calcidiol levels have reached at least 40 ng/ml.

Note: Pay close attention to the abbreviation ng/ml (nanograms/milliliter) because Vitamin D3 levels (calcidiol levels) are sometimes cited in terms of nmol/L (nanomoles per liter) and these numbers are 2.5 times the ng/ml measurement. That is, a reading of 50 nmol/L is just 20 ng/ml. If you’re not careful, you’ll misread the nmol/L level as ng/ml and think that your calcidiol level is higher than it really is.

In summertime, if one is outside a lot and not regularly shielding the body with clothing or sun block it is quite likely that more than enough cholecalciferol is being manufactured by the skin to get levels above 40 ng/ml, but as winter progresses, a large proportion of the population in northern climates will find they are well below that level if they have a 25(OH)D test done. In fact, as I’ve become more interested in this, I’ve encountered a number of people below 20 ng/ml when they’ve ordered the test, at which point even their regular physicians have become concerned.

Dr. Cannell discusses the dosage issues, as well as the toxicity issues and the minute amounts of cholecalciferol needed on his website if you follow the links.

How does Vitamin A affect Vitamin D3 supplementation?

Dr. Cannell is the lead author (of a total of 17 co-authors) on a paper published in 2008 titled Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory Infections, and the Vitamin D Deficiency Epidemic. In that paper, the authors argue that supplementation with Vitamin A in the form of retinols (as opposed to carotenoids found in vegetables) will frustrate the body’s ability to efficiently utilize the Vitamin D3 (calcidiol) stores. He advocates providing needed Vitamin A in the manner nature intended, by eating the right vegetables, so that the body can regulate the needed amounts of Vitamin A on its own. At least this is how I understand his discussion.

This could be important because autistic children are often supplemented with Vitamin A (if website discussion topics are a decent indication) and Dr. Cannell (and 16 other authors) are claiming that it is important not to override the Vitamin D3 processes by supplementing Vitamin A in retinol form. Cod liver oil, for instance, provides Vitamin A in retinol form.

Read Dr. Cannell’s December 2008 Newsletter on Vitamin A Toxicity for a full explanation.

Where can Vitamin D3 supplements be purchased?

I am not qualified to recommend a source, but Dr. Cannell provides links that suggest sources of Vitamin D3 supplements as well as other products including an independent lab to get a blood test to measure your Vitamin D3 (Calcidiol) level. On his Vitamin D Links page, he states that he is just listing the information as a service, but is not endorsing any particular product. As with all consumer products, buyer beware is a good rule to keep in mind.

The next page discusses a study confirming that nutritional supplementation can increase nonverbal IQ and also discusses the possibility that the authors were unknowingly treating the dyslexic subset of the student body.

Next: More Evidence Nutrition Matters, or return to the Home Page