B-Vitamins: benefits and risks of going beyond RDI?


It seems like all the supplements for B vitamins go way beyond RDI. Additionally, they vary significantly from one another.

I know for some micronutrients there is growing consensus that RDI is far from ideal (Vitamin D being perhaps the best example).

Anyone have info about which of the B vitamins offer benefits in large amounts? Or if any should be avoided?

Here are a few examples of supplements: https://www.evernote.com/l/AAJAMcbV9x1J1K-qFEsTZqz_74qq06sKZCs


Here is a decent breakdown of the symptoms of B vitamin overdose.


That’s not a bad breakdown, but I don’t agree with their limit for niacin. That upper limit is based on avoiding “niacin flush reaction,” a minor skin flushing effect that happens only the first time you start taking those doses of niacin.

Generally speaking, the B vitamins have no meaningful negative effects from the levels in over-the-counter “high-potency” multivitamin formulas, and may have some benefits. I suggest looking at the details for each B vitamin on the LPI site to see the specific benefits and potential risks, if any:


I thought you just peed excess of B vitamin away?


The B vitamins are water-soluble, so yes, you pee them away. But not just the excess. You pretty much pee them all away, if more gradually. That’s why we need to consume them every day to keep our levels up.

That having been said, if you consume an extreme excess of something, and it hits toxic levels, it doesn’t matter if you can eventually pee it away - it can still cause problems. For example, hyponatremia - also known as water poisoning.


Niacin flush doesn’t just happen when you first start taking it. It can be a repeatable reaction for some people.

There are numerous sources that say it can certainly have serious side effects from taking too much, and I’d rather take a better safe than sorry approach of there are conflicting studies.


I’m also very safety-conscious; I’m looking for a health benefit, not a health risk.

That being said, you need to keep in mind what a “larger dose” or "too much " is.

The RDI for adult males for Niacin is 16 (14 for females.)

The UL for Niacin intake/supplements is 35 mg based on the risk of the flushing reaction, which is minor and not a health risk, and tends not to persist (at these dosages.)

I take a multivitamin that supplies 190 mg per day, but I take it split into at least two doses. I’ve never had a flush reaction with this product; some people have an initial flush, but reports are that it goes away.

In studies, they have found more serious side effects, such as signs of hepotoxicity (liver damage), “observed at intakes as low as 750 mg of niacin per day for less than three months (84, 85)” (from the LPI Niacin page).

Niacin is used for treatment of dyslipidemia (abnormal fat or cholesterol in the blood) at levels of 1000 mg and 1500 mg per day; at these levels, some people have persistent flushing. Also,you must monitor for liver problems - they are rare, but it’s possible. Here’s a short-term safety study of 148 patients, 1/3 of them dosing at 1000 mg and 1/3 of them dosing at 1500 mg per day. Result: “Four patients discontinued participation because of inadequate glucose control. Rates of adverse event rates other than flushing were similar for the niacin and placebo groups. Four patients discontinued participation owing to flushing (including 1 receiving placebo). No hepatotoxic effects or myopathy were observed.”

So the safety profile of niacin is well established, and the 35 mg upper limit is conservative; most of the few people who flush at that level will not continue to flush. That being said, you can always find someone very sensitive to flushing - note that in the last study I cited, one of the four people who quit the study because of flushing was actually receiving placebo, and not getting any niacin at all!


Aka the nocebo affect :smile:


Then there’s Scientology, which uses niacin and prolonged sweating in a sauna for a “Purification Rundown” that’s supposed to get drugs, toxins and radiation (!) out of your body fat. Hubbard claimed the niacin flush was radiation visibly leaving the body! He thought your body was reliving and reversing old sunburns. And other fun stuff (“Dianazene” was what he called his vitamin mix, mostly a megadose–200 mg.–of niacin):

Dianazene runs out radiation—or what appears to be radiation. It also proofs a person up against radiation in some degree. I have seen it run out skin cancer. A man who didn’t have much liability to skin cancer (only had a few moles) took Dianazene. His whole jaw turned into a raw mass of cancer. He kept on taking Dianazene and it disappeared after a while. I was looking at a case of cancer that might have happened.

Good times.


Well, if you’re going to drown in it…


Hyponatremia doesn’t refer to drowning.



It’s a figure of speech.