Your hormones are doing an intricate relay race every month. Specifically at play are estrogen, progesterone, and follicle stimulating hormones. These will go up in anticipation of supporting a pregnancy and then go down when its job is complete.
Fluctuating or irregular hormones are what can lead to many symptoms associated with periods and menopause. The purpose of seed cycling is to regulate estrogen in the first half of your cycle and then progesterone in the second half. The seeds involved are high in essential fatty acids (EFAs), which are necessary for regular hormone production, and can also help in binding and excreting excessive hormones.
A common approach is to eat 1 tablespoon each of freshly ground flax and pumpkin seeds per day for the first 13 to 14 days of your menstrual cycle (aka the follicular phase). Then during the second half (aka the luteal phase), eat about 1 tablespoon each of ground sunflower and sesame seeds per day until the first day of your next period when your cycle starts again.