Vitamin B12 and estrogen have a complex relationship with each other.
The research on this topic appears unclear because vitamin B12 can have a different effect on estrogen depending on how high estrogen levels are.
In other words, it appears that vitamin B12 has a regulating effect on estrogen in the body, but more research is needed.
I’ll break down the relevant research that I’ve read on this topic in this short post.
Table of Contents
The Relationship Between Vitamin B12 and Estrogen
There’s a few basic things we need to go over first.
A few terms you’ll see shortly are estrone and estradiol, which are 2 of the most common forms of estrogen in the body.
One thing that the body needs to use to break down estrogen in certain situations is vitamin B12, which is a big reason why the levels of these 2 substances are interlinked (1).
Both are very important for good health, but need to be kept in the right balance of each other.
How Vitamin B12 Supplements Affect Estrogen and Other Hormones
There’s not a ton of research looking at the effect of vitamin B12 on estrogen, but there is some, and it is high quality.
A 2021 study had 259 women take a combination of vitamin B2, B6, and B12 (2).
After adjusting the results for several factors like age, race, and body mass index, the researchers found:
- Vitamin B12 intake had a slight negative correlation on estradiol (estrogen) levels, but it was not statistically significant.
- Vitamin B12 intake had a positive and statistically significant impact on testosterone and free testosterone.
One other study looked at the effect of supplementing vitamin C, vitamin B6, vitamin B12, and folate for 8 weeks on obese postmenopausal women (3).
They found that:
Estradiol (estrogen) levels rose from a median of 22.0 pg/mL to a median of 27.8 pg/mL
Despite the short study length, the supplements had a significant effect, although it was more than just B12.
Postmenopausal women are expected to have lower estrogen levels. For reference, healthy premenopausal women typically have estradiol levels between 30-400 pg/mL.
It’s a reasonable time to note that nearly all research on estrogen and vitamin B12 is done in women, so it’s hard to extrapolate anything to men.
A lot more research is needed on this topic. However, it appears that vitamin B12 intake doesn’t affect estrogen levels significantly in women with healthy levels of both to begin with. However, vitamin B12 may raise estrogen levels in women with low estrogen levels.
Excess Estrogen Correlates With Low Vitamin B12 Levels
We can also look at this relationship from another perspective.
There are many side effects of vitamin B12 deficiency like low energy levels, depression, and even brain damage in the long term.
While there are many mechanisms involved, there’s research that suggests that some of these side effects may be caused by a vitamin B12 deficiency resulting in excess estrogen.
While not having enough estrogen can be bad, too much is also a negative thing.
This correlation can be seen in studies on contraceptives. Taking an oral contraceptive that contains estrogen leads to the suppression of vitamin B12 and can lead to a deficiency (4).
Presumably, vitamin B12 is being used to process the excess estrogen so that it can be disposed of.
Putting all this together, we can speculate that vitamin B12 might lower estrogen levels if they’re too high, or raise estrogen levels if they’re too low.
Summary: Vitamin B12 and Estrogen
Not only is this a complex topic that appears to have different results depending on the starting levels of both vitamin B12 and estrogen, there really isn’t a lot of research on this topic.
And the research that is available isn’t particularly conclusive.
While other substances are also involved, it does appear that having either one out of balance could cause the other one to go out of balance as well.
From a practical standpoint, it’s important to monitor both vitamin B12 and estrogen levels with your doctor when possible.