Fortunately, you don't need to change your diet too much while breastfeeding—all the vitamins you take in will naturally go to your breast milk first. This means it's nearly impossible to deprive baby of what they need. However, there are a few things that you should cut down on while baby's nursing.
You don't need to completely cut out fish, but the FDA recommends that nursing women (as well as those trying to conceive or pregnant) should limit fish intake because of its mercury content. Can't do without a good tuna sandwich now and then? Just remember that the FDA advises no more than six ounces of canned albacore ("white" tuna) a week.
Opinions on this one are mixed, but the American Academy of Pediatrics says alcohol in moderation (one or two drinks a week) is fine, while the March of Dimes recommends against drinking any alcohol while breastfeeding. Either way, you definitely need to keep an eye on your intake. Alcohol may make it harder for your body to product breast milk, and trace amounts can show up in your milk and may harm or bother baby. If you do have the occasional drink, wait at least two hours afterwards before nursing baby.
Your morning cup of coffee is fine, but don't go overboard. Too much caffeine can lead to a fussy baby who doesn't want to sleep. (Meaning you'll need more caffeine to stay up with her... meaning she'll be even less into sleep... meaning you'll need more... you see where this is going, no?) Remember, caffeine can be found in soda and tea as well as some of those over-the-counter medications you may be taking for common ailments. Just to be safe, always read the label.
Though your diet doesn't need to be completely bland, you might need to forfeit some flavor... especially if you're a lover of foods with a kick. Too much spice can make baby gassy and uncomfortable, so play it safe and avoid foods strongly seasons with spices like garlic or chili powder. Of course, every baby is different, so if yours doesn't seem bothered by spice, it's fine to indulge now and then.
We wouldn't normally knock a vitamin, but this one has actually been linked to mild diaper rash in babies. Watch vitamin C rich foods, especially fruits like oranges and grapefruits. You don't need to completely avoid the vitamin, but be especially careful if you notice that baby seems to react after you eat citrus.
Looking for foods you can eat? Try these 10 breastfeeding superfoods.