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Vitamin C
Flying off the handle at the littlest thing? Your hormones might be to blame. "At age 35, you start to run out of ripe eggs in your ovaries, which means you're making less progesterone," says board-certified ob-gyn Sara Gottfried, MD, author of Younger. Progesterone keeps you calm and prevents those harried moments. To keep the hormone in the right range, you need ample vitamin C, she says. Though you can eat rich sources of vitamin C—strawberries, kiwis—a higher amount has been shown to make a difference in progesterone levels.

How much to take: 750 to 1,000 mg daily, recommends Gottfried.