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I understand the B Vitamins are water-soluble, so it is more difficult to take too much -- you flush them out of your system (as opposed to fat-soluble vitamins, which can stay with you for a long time).

However, is it possible to take so many B vitamins that they start to become toxic?

What are the negative effects?

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  • What would be your worry for taking to much? You don't have to take too many vitamin pill ;-)
    – Ivo Flipse
    Commented Mar 31, 2011 at 5:23
  • @Ivo I once tried an energy drink - shot size - that had over a year's supply of vitamin B in it (according to FDA recommendations).
    – G__
    Commented Apr 1, 2011 at 1:56
  • Off topic due to new FAQ, questions need some relation to exercise.
    – Baarn
    Commented Sep 20, 2012 at 18:43
  • This is now deemed as off-topic per the FAQ and will be closed. Only nutrition questions related to fitness are on-topic.
    – Nathan Wheeler
    Commented Sep 20, 2012 at 19:42

1 Answer 1

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Yes but it depends on which B Vitamin...

Here's the complete list.

thiamin (B1):

No known toxicity from oral intake.

riboflavin (B2):

No evidence of toxicity based on limited human and animal studies

niacin (B3):

Intake of 3000 mg/day of nicotinamide and 1500 mg/day of nicotinic acid are associated with nausea, vomiting, and signs and symptoms of liver toxicity. Other effects may include glucose intolerance, and (reversible) ocular effects. Additionally, the nicotinic acid form may cause vasodilatory effects, also known as flushing, including redness of the skin, often accompanied by an itching, tingling, or mild burning sensation, which is also often accompanied by pruritus, headaches, and increased intracranial blood flow, and occasionally accompanied by pain.[9] Medical practitioners prescribe recommended doses up to 2000 mg. per day of niacin, usually in time release format, to combat arterial plaque development in cases of high lipid levels.

Large doses (Ie, greater than 1000mg) are usually only taken as a measure to lower cholesterol in place of statins or other prescribed medications.

Also, the 'slow release' or 'no flush' formulas have been known to cause liver damage if taken in large doses.

pantothenic acid (B5):

No known toxicity

pyridoxine (B6):

All effects are unconfirmed: (peripheral) sensory neuropathy [causal association with intake of vitamin B6 is likely]; dermatological lesions [causal association is unlikely]; B6 dependency in newborns [causal association is also unlikely].

biotin (B7):

No known toxicity

folic acid (B9):

Masks B12 deficiency, which can lead to permanent neurological damage

cobalamin (B12):

Acne-like rash [causality is not conclusively established].

Note: All the information presented in block quotes is from Wikipedia.

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  • So which am I likely to have in my diet or regular food? I would somewhat reorganize your answer into no known toxicity and the ones that have some effects. Just put them in a bullet point or something :-)
    – Ivo Flipse
    Commented Mar 31, 2011 at 5:22
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    @Ivo All of them should be present in a remotely healthy diet. (If you only eat hot dogs, you probably don't have enough folic acid ...). Unless you're eating only papaya 24/7 or something, it's also safe to add in a B-vitamin supplement (since the toxicity levels are so high/nonexistent). See latimes.com/features/health/… (focuses on energy drinks, but has that info)
    – Matthew Read
    Commented Mar 31, 2011 at 13:41

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