Magnesium
Some of the best evidence for PMS and cramps. Around 200-400 mg/day (glycinate form is best tolerated) may reduce bloating, mood symptoms, and cramping over 2-3 cycles. Found in leafy greens, nuts, seeds, dark chocolate.
Vitamin B6
Studied for PMS mood symptoms (irritability, low mood). Doses up to ~100 mg/day have evidence, but don't exceed that without medical advice - too much can harm nerves. Often combined with magnesium.
Iron
Important if you have heavy periods, which can cause iron deficiency and fatigue. Don't self-prescribe high doses - ask for a ferritin blood test first. Get iron from red meat, lentils, spinach (pair with vitamin C for absorption).
Vitamin D and omega-3
Vitamin D supports overall hormone and bone health; many people are low, especially in winter (1000-2000 IU/day is common). Omega-3 (from oily fish or supplements) may reduce period pain and inflammation.
Food first, then supplements
A balanced diet covers most needs. Supplements help fill gaps or target specific symptoms - they don't replace good food, sleep, and movement. Talk to a doctor before starting, especially if you're on medication, pregnant, or trying to conceive.