In Your 30s

Folic Acid
If you plan on having babies before now, then you definitely want to move this vitamin up a decade, but since many women are getting pregnant in their 30s, now is the time to start taking folic acid (even before you actually start trying). It’s key to baby-brain development — so obviously you don’t want to mess with not having enough of that. And a little goes a long way — experts suggest about 1 mg per day (often the number in a multi, but check the label to be sure).

Vitamin C
This immune-booster is like the Jennifer Aniston of the vitamin world — it just doesn’t get old. No matter how many new kids on the block come in and try to trump its stay-healthy power, this tried-and-true vitamin always comes out on top. Of course, oranges and citrus fruits in general stand out as the vitamin C powerhouse, but really all green veggies have it, too, as well as many fruits (think: blueberries). Whether it’s in pill or powder form, it doesn’t really matter in terms of how your body takes it in — but opt for a "buffered" formula (as in the C is not solo, but mixed with say, calcium, magnesium, potassium, etc.).

“A cocktail is easier on the stomach, and then you get benefits of other minerals, too,” says Morrison. As for OD-ing on C once winter strikes and germs are seemingly everywhere? “Anectodately, people swear by it, but there’s no real proof that when you take way more than usual that it does anything for you,” says Gans. “Better to take it consistently at a regular dose.” But if you do take too much: Don’t worry. The whole you-pee-it-out thing is true — because C is water-soluble. Aim to get around 1,000 mg a day (also typically the amount in a multi) but you can take a little extra to be sure you get it all, if you want.

Probiotics
Anyone who has dealt with a yeast infection knows that probiotics can be life changing. While, of course, any female can benefit from some good bacteria (especially when on prescription antibiotics), Morrison says he tends to have 30-something women who also deal with some digestive issues, and probiotics can help regulate their um, movements. There is no one-size-fits-all magic number in terms of quantity — more of a what’s-good-for-you basis (we wouldn’t expect anything less from our lady parts). “The reality is that every person has their own normal types and amounts of good bacteria, so it’s hard to put an overarching quantity that’s right for all — so, instead test out different kinds and see what you get the best results from,” says Morrison. “But what you do want to do is make sure that it has a combo of lactobacillus and bifidobacterium.”