B12 - How much is too much?

mrsD · 04-27-2013, 07:31 AM

Can you link to the article that high B12 causes blood clots?
Was it Livestrong? That site is often spotty in its information.

It is important to watch for odd internet sites...that do not have scientific bibliography to corroborate their statements.

This is an example of one that provides a good bibliography:
http://lpi.oregonstate.edu/infocente...ns/vitaminB12/

Quote:

No toxic or adverse effects have been associated with large intakes of vitamin B12 from food or supplements in healthy people. Doses as high as 1 mg (1000 mcg) daily by mouth or 1 mg monthly by intramuscular (IM) injection have been used to treat pernicious anemia without significant side effects. When high doses of vitamin B12 are given orally, only a small percentage can be absorbed, which may explain the low toxicity. Because of the low toxicity of vitamin B12, no tolerable upper intake level (UL) was set by the Food and Nutrition Board in 1998 when the RDA was revised (6).

and:

Quote:

The IOM did not establish a UL for vitamin B12 because of its low potential for toxicity. In Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline, the IOM states that "no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals" [5].

Findings from intervention trials support these conclusions. In the NORVIT and HOPE 2 trials, vitamin B12 supplementation (in combination with folic acid and vitamin B6) did not cause any serious adverse events when administered at doses of 0.4 mg for 40 months (NORVIT trial) and 1.0 mg for 5 years (HOPE 2 trial) [62,63].

http://ods.od.nih.gov/factsheets/Vit...hProfessional/

Also a search on PubMed brought up no papers indicating clotting risk.

I did find on Mayo's site... a warning for people with cardiac stents. Because B12 may increase blood cell production, people with stents are to not use really high doses so as not to thicken the blood. The same goes for those with the genetic disease polycythemia Vera, which causes thickened blood with too many red cells. These are special situations, however. A simple CBC will show if there are too many red cells. Just about everyone here has had that test.

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B12 - How much is too much?

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