[surferjoe2007]

I've looked into it a bit and haven't found any clear answer on whether or not NBE interferes with birth control. Vendors say no. Others say maybe. In theory the weaker phytoestrogens could compete with the stronger estrogen for spots in estrogen receptors. That might decrease their impact. I'd think a billion people would be complaining if it was a common problem, but at the same time I haven't found any confirmation that people's birth control worked fine either.

Since progesterone decreases estrogen it might theoretically interfere too. Fennel, cinammon and saw palmetto are less likely to interfere sine they work on other hormones (prolactin, insulin and decreasing testosterone) but I still can't be certain. Cinammon might also have phytoestrogens, for example.