Folic Acid: What If You Take Too Much?

Folic acid (a form of vitamin B9 found in many foods, as well as popularly taken as a supplement) is critical to good health.

Indeed, that is part of the definition of “vitamin”.

However, it is possible to have too much of a good thing!

Highs and lows

Folic acid is essential for DNA repair, methylation, and fetal neural development, but both insufficient and excessive intake pose risks.

Insufficient intake can result in raised homocysteine levels (that’s bad), and resultantly, increased stroke risk. It can also cause problems in fetal neural development, but obviously that’s only important if you’re pregnant. Still, it’s a reason that folic acid is often marketed as an important thing to ensure plenty of during pregnancy.

As for excessive intake, that falls into two main categories. We’ll quote the breakdown of this directly from a paper that we’ll share in a moment, so pardon it’ll be jargon-heavy in the bullet points, but we promise we’ll explain it all underneath:

Neurotoxicity:

• High folic acid mimics glutamate-like excitotoxicity, similar to kainic acid (KA).
• Methyl-THF competes with KA for receptor binding in the brain.

Inflammation:

• Excess folic acid (>40 µg/mL) inhibits anti-inflammatory cytokine IL-10.
• Hypoxia increases inflammation via HIF-1 pathway → IL-1β and TNF-α production.

So, about that neurotoxicity: basically, an excess of folic acid can mimic certain neurotransmitters, which may sound like a good thing, but because it’s showing up in unexpected quantities in unexpected places, it can kill neurons in the CNS, which needless to say, is definitely a bad thing.

See also: The mechanism of kainic acid neurotoxicity

And, about that inflammation: there are two main things going on here, which are that it simultaneously excites some inflammatory systems and inhibits some anti-inflammatory systems. Now, both of those systems are supposed to exist and function, but playing them against each other, and without good reason, results in an overall dangerous increase in inflammation.

To make matters worse… Remember that whole “folic acid is needed for fetal neural development” thing? Taking it in excess can overstimulate neural stem cell proliferation, and while you may think “having more stem cells is surely a good thing”, please remember that excessive proliferation of any kind of cell is basically the hallmark of cancer. So, definitely not something you want in your brain, or anywhere else in your body, really.

You may be wondering what that bit about hypoxia was. In few words: excess folic acid can worsen sleep apnea due to disrupted methylation (we’ll explain this in a moment) in hypoxic (i.e. “not enough oxygen”) conditions (i.e. what happens when you stop breathing during sleep apnea).

About the disrupted methylation: ok, we’re having a lot of terms that need explaining today, but this one’s a good one to understand. You know how vitamins B9 and B12 are often discussed at the same time and pertaining to the same groups of people who are likely to be deficient in both?

Vitamin B12 deficiency combined with high folic acid can trap folate metabolites (i.e. what your body produces when metabolizing folic acid) and raise homocysteine (which we discussed up top), increasing risks of anemia, cognitive decline, and neuropsychiatric disorders.

We’ve got some good news, but before we get to that, here’s the paper we’ve been mostly working from today:

How Increased Dietary Folic Acid Intake Impacts Health Outcomes Through Changes in Inflammation, Angiogenesis, and Neurotoxicity

How to do it better

Of course, sticking to recommended dosage guidelines is important, but you can also skip folic acid entirely (yes, really) and go with a different vitamer of vitamin B9 (a vitamer is a variation of a vitamin), namely, l-methylfolate, which can help dodge a lot of the methylation issues and thus related problems we talked about.

See also: Which B Vitamins? It Makes A Difference

Please still stick to the recommended dosage guidelines of course, but it’s safer than folic acid and as a bonus, you’ll also get more “bang for buck”.

Want to try some? We don’t sell it, but here for your convenience is an example product on Amazon 😎

Enjoy!