Sea Kelp & the contraceptive pill?

Q:My boyfriend has been taking Sea Kelp for a couple of months and he feels so much better. I am having problems with my weight and I bite my nails so this would be the perfect thing for me to take. However …… does anyone know if it affects the contraceptive pill i.e. Microgynon? I know St. Johns Wort does and the websites all just say “..some herbal remedies” may affect it. Any help would be gratefully recieved!!