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Vitamin D, fortification, and Subway

Posted on: August 4, 2011   by  John Cannell, MD


Last month Professor Rebecca Mason of the University of Sydney and her co-authors wrote an excellent review of vitamin D.

Mason RS, Sequeira VB, Gordon-Thomson C. Vitamin D: the light side of sunshine. Eur J Clin Nutr. 2011 Jul 6. doi: 10.1038/ejcn.2011.105. [Epub ahead of print]

With two references, she confirmed what I always thought likely: higher calcium intake increases vitamin D levels. It makes sense, as less vitamin D is used up for absorbing calcium if calcium intake is high enough to trigger only passive calcium absorption.

I also liked her reiteration of vitamin A’s ability to interfere with the function of vitamin D, something I have written about in detail. I continue to think cod liver oil is confounding many vitamin D studies.

In several places, Professor Mason questions whether ethical concerns will mean that randomized controlled trials will never be done. After all, do you want to be randomized to the 600 IU/day control group? Not me.

I also liked her brief discussion of a wonderful paper that I wrote about last year on the study of 675 fresh cadavers. The authors compared bone biopsies and vitamin D levels of the cadavers to conclude that vitamin D levels of at least 35 ng/ml are needed for healthy bones, a study the recent FNB must have missed.

My only criticism is her failure to realize that food fortification is essential for large subgroups of the globe’s population. For example, African Americans are unlikely to seek sun exposure or take vitamin D supplements, proven by the fact that so many black women of childbearing age have vitamin D levels less than 10 ng/ml.

It appears as though some food companies are picking this up. Yesterday, Subway (the world’s largest food chain in terms of restaurant units) announced they will begin adding about 100 IU of vitamin D to the bread they use to make their subs.

Subway’s ‘Healthy’ New Bread Will Include Vitamin D, Calcium. Huffington Post, 2nd Aug 2011.

Although 100 IU is a menial amount of vitamin D, every little bit helps. And with Subway’s large and global influence, they might even help spread a little awareness.

8 Responses to Vitamin D, fortification, and Subway

  1. boston

    what i don’t see a lot in the literature about—is the fact that vit d should be taken with fat—
    no wonder it seems to be best absorbed when one takes it with the largest meal of the day. there’s probably more fat in it.
    isn’t that what fat soluble vitamin means?

    i haven’t read dr. Horlick’s new book, but i understand that he does not mention that vit d needs to be taken with fat. if that is correct, how can that be?

    also, you don’t see a lot in the literature about taking it with the co-factors.

    • Dana Clark

      hi chibaby33 –
      according to dr. cannell, vitamin D can be taken at any time of day, with or without food or other supplements, and it should be absorbed just fine. the exception to this would be those who may already have absorption issues present. there are also some D3 supplements out there which are water soluble, such as bio-tech pharmacal’s D3.
      unfortunately, i am not able to answer your question as to how a fat soluble compound can be absorbed without fat…i’m hoping one of the experts will chime in here…

      – dana clark
      web director, vdc

  2. boston

    your answer from Dr. Cannell does not explain the fact (if I am correct) that he has a vitamin d supplement that he sells that have several co-factors in them…
    AND , according to my recollection, he talked about them in his past newsletters (before you changed your format)…. ie MAGNESIUM, K2, ZINC AND I THINK BORON ALSO…..
    Both that past article and your statement above regarding what he said—seemingly conflict with his statement above regarding not needing any other supplements with it….
    I believe I still have the article from the newsletter–as i have sent it to many of my friends.
    Please clarify.

  3. Brant Cebulla


    See this study on the absorption of vitamin D when fortified in milk (contains fat) vs. orange juice (does not contain fat): http://www.ajcn.org/content/77/6/1478.full

    They found that the body absorbed vitamin D just as well in the orange juice as the milk. The study does not speculate as to why this is.

    Studies like the following, suggest that there are unknown factors in absorbing fat-soluble vitamins, and it is not simply a matter of the bioavailability of fat: http://www.ncbi.nlm.nih.gov/pubmed/12964802

    Finally, here is a good, easy read on how fat and fat-soluble vitamins behave in your intestine: http://health.howstuffworks.com/wellness/food-nutrition/vitamin-supplements/fat-absorb-vitamins.htm

  4. boston

    thanks for the info, Brant,
    on the one hand, from what I read that you sent me about the co factors, it seems that those co factors, ie. k2,magnesium, etc. DO help to absorb the d better —yet you write above that Dr. C says you don’t have to take D with anything special to have them absorb….
    and to add to this confusion—the articles written in your newletter way back regarding the “co-factors” as being necessary for absorption of D–and the fact that Dr. Cannell has produced a D vitamin bottle with these co-factors in them—seems to be in conflict with his saying that you don’t need anything to get it absorbed. Has he changed his mind due to the testing you sent me to read???
    and how then do you explain all those descriptions of what vit k2, magnesium,etc. do regarding the vitamin d in your body?

  5. Brant Cebulla

    I think you’re over thinking the whole matter. The aforementioned co-factors do help you metabolize vitamin D, and they also increase the efficacy of vitamin D.

    Now, if someone was taking vitamin D supplements over a long period of time, and the health benefits of vitamin D were still not noticeable, then the logical question is: could you be deficient in some co-factors?

    You can obtain the co-factors in a healthy diet consisting of vegetables and lots of leafy greens (magnesium, K1), nuts (magnesium) and some meat (K2, zinc). If your diet, for whatever reason, excludes some of those food groups, then you could look into supplementing with those vitamins as well.

    What is your particular concern about co-factors?

    Edit: I apologize for the use of the word “absorption.” Important distinction: co-factors help you metabolize vitamin D, not absorb.

  6. boston

    It took me a while to find this blog–perhaps you can tell me how to access it on the site. when i put in vitamin d, fortification and subway, into the search engine, I can’t find it….what else should I be putting into the search engine to find it? Fortunately, I found the original blog in my “sends.”

    In regard to my concerns about co-factors–it’s just that in the older newsletters from Dr. C. there was a great deal of emphasis put on having them for “metabolizing” the d. ( I’m not sure if those articles said “metabolizing” or “absorbing.” I’d have to look them up to be sure.)

    I think I’m obsessing over this because I had put a lot of stock in those articles, to the extent that I told everyone i know that they needed the co-factors to get the full benefit of the d…. I try to be correct about something like this, especially because everyone I know is buying the d vitamins now with the co-factors in them because of what I told them….I do know that Dr. Horlick in his new book(as I mentioned in another blog), says that you can take them with or without food….so the fact that Dr. C’s newsletters and bottles of vitamin d suggest that they need to be taken with the d–is the reason I wanted to clarify this…….I do realize that some foods give one these things—-so what i think you’re saying is that just in case you are not getting everything–it wouldn’t hurt to take the supplements.
    Perhaps more evidence has come up that has changed the emphasis on these co factors….
    I hope so…..

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