If you’re a woman with any menstrual irregularities, there are a number of reasons why you might want to consider adding Vitamin B6 to your regimen, over and above what you might be getting in a multivitamin.

Vitamin B6 and Estrogen Metabolism

The liver breaks down estrogen into one of three metabolites (or breakdown products) called 2-hydroxyeone (2-OH), 4-hydroxyestrone (4-OH), and 16-hydroxyeone (16-OH). Their numbers are also listed from best to worst: 2-OH is gentle and balancing (and not associated with cancer), while 16-OH is a strong estrogen metabolite and has been associated with cancer. Vitamin B6 encourages estrogen to break down into 2-OH instead of 16-OH, which both decreases cancer risk, and decreases the strength of the estrogen metabolites on the way out of the body.

This means fewer estrogen dominance symptoms during PMS, including less breast tenderness and fewer cramps.

Vitamin B6 and Progesterone

After ovulation (when the ovary releases an egg), the follicle where the egg used to be develops into the corpus luteum. The corpus luteum produces progesterone during the second half of the menstrual cycle (called the luteal phase), and on into the first trimester of pregnancy, if pregnancy occurs that cycle. Progesterone is “pro-gestation”: it’s the hormone that tonifies the endometrial lining to make it nutrient rich for a fertilized egg.

All that to say, Vitamin B6 is necessary for the production of the corpus luteum. Low B6 means low progesterone, which is another way you can end up with estrogen dominance. (It also means you’re likely to have a luteal phase defect, meaning a luteal phase shorter than 10 days after ovulation–which is a problem if you’re trying to get pregnant.) If the cause of a short luteal phase is low B6, supplementing with the vitamin usually corrects the problem within a few cycles.

Vitamin B6 and Fluid Retention

Vitamin B6 is a natural diuretic, because it keeps your electrolytes (sodium, potassium, and magnesium especially) in balance. It won’t make you pee if you’re balanced already—but if you’re too high in sodium, for instance, you’ll retain fluid, because water follows sodium. Vitamin B6 will encourage sodium excretion through the kidneys—and again, water follows sodium, so you’ll pee more too. (If you eat a whole foods based diet, this will be less of an issue, since you won’t have nearly as much sodium in you to begin with.)

I suspect part of the reason why fluid retention often occurs premenstrually is because Vitamin B6 is otherwise occupied making the corpus luteum, and perhaps there isn’t enough left over to also adequately regulate electrolyte levels. But that’s a guess.

Vitamin B6 and Neurotransmitters

Vitamin B6 is also a necessary cofactor (required to make the enzyme work) for neurotransmitters, including GABA, serotonin, melatonin, dopamine, norepinephrine, and epinephrine. Lower levels of B6 will lead first to lower serotonin and GABA, which is part of why you can feel depressed and anxious around your period.

Why You Might Be Low in Vitamin B6

Stress is probably the biggest one: progesterone is the precursor for cortisol, the stress hormone, and progesterone is synthesized in part by B6. If you’re stressed, you’ll deplete your levels of both progesterone, and B6.

Birth control disrupts gut flora and decreases nutrient absorption, including Vitamin B6.

Alcohol also depletes B vitamins in general (which is one of the reasons it can decrease fertility rates). If you have more than a few drinks per week and have PMS, you might want to either cut back, or supplement.

Dosing with Vitamin B6

You can be intentional about getting Vitamin B6 from your food: it’s found in trout, blueberries, organ meats, molasses, green leafy veggies, and whole grains.

Or, you can take a supplement. Be aware that it is possible to overdose on Vitamin B6; if you do, you’ll get tingling and numbness in fingers and toes that reverses when you stop or lower your dose.

This is the one I most commonly prescribe, starting at 50 mg daily.