All the minerals of course, but especially cal/mag with D worked for me, but not without a hefty dose of EFAs. When I found the right amounts for me and good sources (I like New Chapter Bone Strength and Flora Flax + DHA with black currant seed oil), it worked wonders for my cramps and other PMS symptoms.
Actually, Cathy Crystal suggested that I use cramp bark tincture every 15 minutes for acute cramping, and wow, why was I using ibuprofen for so many years when the name of this herb says it all? The key was the every 15-30 minute dose. It worked amazingly.
Another obvious part of my foundation for PMS/cramping prevention is regular exercise. Haven't tried cinnamon exactly for that problem, but I guess it has been working.
Be careful if you use magnesium for acute cramping-as you may know, too much desperation can give you some explosive diarrhea

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