Why is my breast milk sour?

Are you or could you be pregnant? That could explain a change in taste and color. If you are pregnant, that's not really your milk going "sour". It just tends to change in taste due to hormone fluctuations, and it will eventually turn back to colostrum, which is golden in color.

Some women also experience a change in taste when they're about to menstruate, or when they're on their period: http://www.breastfeed-essentials.com/menstruation.... Hormonal changes are also responsible for that.

You tasted it to know it's sour, or just thinking it is because of baby's reaction to nursing? personally I really don't care if you tasted it...I know of only one mom that didn't! I ask because if it is truly sour there are 2 reasons I can think of off the top of my head. 1.) you've been eating something sour and it cause you milk to follow suit, which is common with other foods like garlic, onions, spicy, etc. I don't remember hearing about sour foods turning the milk sour flavored, but it wouldn't surprise me. 2.) You're pregnant and your hormones are reacting and changing you milk flavor! Either way, if baby doesn't like the flavor, baby won't take. Aside from changing your diet, you can't do much of anything else to change baby's mind!

Breast milk can go bad just like any other perishable food. It is good in the fridge for about 5 days or it can be frozen for up to 6 months.

Take a pregnancy test. I do not know why it would taste sour... Normally it is relatively sweet I believe.

not enough nutrition