16 December 2016

41,667% daily value of a vitamin


Part of the label for a bottle of vitamin B12 tablets.

I'm a bit puzzled.  If the once-a-day tablet represents 417 times the recommended dose, does that mean the manufacturer assumes that everyone taking it is deficient in intrinsic factor?  Does the "daily value" only apply to intravenous administration?  If that's the case, shouldn't the 2500 micrograms then become the recommended "daily value" for oral intake?

I suppose I could look this up, but I thought it would be faster to ask here, because some reader will know the answer.  Thanks in advance.

14 comments:

  1. First, you're misreading the label. If 100% is the recommended daily amount, then 41,667% is a 416x dosage, not a 41,000x dosage. Still a massive overdose, but two orders of magnitude different.

    Now to your question. I'm no nutritionist, but my understanding is that the Daily Value is what would be considered "sufficient," IE a minimum. For some nutrients, just a little more will become poisonous (and even water is deadly in large enough quantities), but apparently that's not the case for B12. "In the case of vitamin B12 there is no [intake limit], as there is no human data for adverse effects from high doses." https://en.wikipedia.org/wiki/Vitamin_B12#Dietary_Reference_Intake

    Finally, just because that's the amount of B12 in the pill doesn't mean your body will absorb all of it. I believe I've read that most of the content of supplements passes through the body without being absorbed.

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    Replies
    1. Tx, Kyle. I actually knew the % terminology - I was just typing too fast. Fixed.

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    2. Seems the actual RDA is 2.4 micro grams, which means this is over 1000x the RDA. I wonder if it is a labeling mistake? Confusion of mg vs mcg over multiple copies.

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    3. Apparently vitamin b12 supplements are very poorly absorbed (1% is absorbed) so 2500mcg has been suggested for vegans who have dietary intake (and would be aiming to absorb their RDI of 2.5mcg)

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    4. Oops. That was supposed to read "vegans who have no dietary intake of vitamin b12 in food"

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  2. I was told that the RDA as given was worked out by taking the what the average person needs and increasing it by two standard deviations.

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  3. it's just an european typo : comma instead of point. read 41.667%

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    Replies
    1. Made in the USA, so nope.

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    2. Yeah, I'm going with this solution as well. Note that 41.6666... (which becomes 41.667 when rounded off at 3 digits) is exactly one third of 125.

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    3. Hmmm, or maybe not. There are several other discussions on the matter that have the exact same figure, but without periods or commas. Odd.

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  4. B12 is a water soluable vitamin. It really doesn't matter how much is put in as the excess is excreted. It may be cheaper for them to out in the excess or maybe it's marketing (more is better?). If you look at vitamins K, A, D, E, the manufacturers are more careful about putting in excess (though they still do). These are fat soluble and sustained high doses can eventually be toxic.

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  5. The recommended Daily Value is released by the US FDA. It represents what the FDA considers the "correct" amount of that nutrient to be for an adult human. Some manufacturers make pills with a much larger dose than the FDA recommendation (such as this one) due to disagreement with the US FDA, or for specific *non-regular* uses, which is often called "megadosing". B12 megadosing is intended to supplement a B12 deficiency (either through a natural issue or due to a medication-induced reduced absorption), or to provide a temporary energy boost, or to alleviate some forms of depression.

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    Replies
    1. Make that "some forms of depressive symptoms", rather than the broader "depression".

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  6. This reminds me of the pseudo-scientific megavitamin therapy ideas advocated by Linus Pauling and others in the late 1960s. They were still kicking around in the early of the days of the internet when I first got involved in scientific skepticism. Here is an old site refuting vitamin megadosing.

    Specifically w.r.t. B12 is states:
    Apart from these specific applications, there is no known benefit from the consumption of high doses of vitamin B12 Herbert [51] has commented accurately that its lack of toxicity and attractive red colour in solutions makes it an "ideal placebo" used extensively by many physicians. However, this is an expensive and unjustified waste of money.

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