For optimal nutrition, don't let your spinach sit around too long before you eat it.

Packaged spinach can lose as much as half of its health-boosting carotenoids and folate in as few as 4 days after you bring it home from the market, research shows. This is true even if the spinach is refrigerated. Try to eat fresh spinach within a day or two of purchase.

Although fresh spinach may lose much of its nutrition in as few as 4 days after purchase, spinach that is frozen and packaged soon after harvesting will retain much of its nutritional value. Eating fresh or frozen fruits and vegetables is a great way to load up on health-boosting vitamins, minerals, antioxidants, and phytochemicals. Leafy greens such as spinach are a great source of folate, a B vitamin that protects the heart by reducing homocysteine levels. Folate is important for the synthesis of DNA, too, making it crucial for pregnant women. Spinach also provides a significant dose of carotenoids, a class of powerful antioxidants.