Vitamin B6 is important in maintaining a healthy cycle, yes. But it won't be simply due to this and it's best to ensure you are getting all the nutrients your body needs on a daily basis as well as for supporting fertility and a healthy cycle.
If you are lacking in certain nutrients, this can cause hormonal imbalance and also it's important to remember that hormonal imbalance is linked to an imbalance in healthy gut bacteria too.
Sometimes it's difficult to incorporate everything you should have into your daily diet for various reasons, so taking a supplement could be helpful, but the best way by far is to ensure a healthy balanced diet and also a reasonable exercise regime is important too. There are so many things all linked together that can impact on your cycle and fertility! Vitamin D, depending on where in the world you are (here in the U.K. vitamin D deficiency is hugely common during autumn/winter because we don't see much in the way of sunshine in the U.K. especially during these months and they do seem rather long!), can be difficult to maintain, and this plays a part in fertility. You can get certain foods fortified in vitamin D and also supplements, in some instances you can get supplements prescribed by your doctor if you are deficient.
If you are concerned you may be deficient in anything it may be worth asking for bloods to be carried out to take a better look.
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