Although it will not produce the magical effects that Popeye enjoyed, spinach is most definitely good for you. It is exceptionally rich in carotenoids, including beta carotene and lutein, and also contains quercetin, a phytochemical with antioxidant properties. Spinach is rich in vitamins and minerals, particularly folate (folic acid), vitamin K, magnesium, and manganese; it also contains more protein than most vegetables. (Although the protein is incomplete spinach and other leafy green vegetables are low in the amino acid methionine, it is complemented by the protein in rice and other grains.)

Raw spinach is a healthy addition to salads, but to get the full benefit from this vegetable , eat it cooked at least some of the time. Cooking makes the antioxidant carotenoids responsible for much of spinach's nutritional potency easier for the body to absorb.

Loose spinach is easier to evaluate for quality, since you can examine each leaf individually. Select small spinach leaves with good green colour and a crisp, springy texture; reject wilted, crushed, or bruised leaves, and those with yellow spots or insect damage. Fresh spinach should smell sweet, never sour or musty.
Look for stems that are fairly thin; coarse, thick ones indicate overgrown spinach, which may be leathery and bitter. If only bagged spinach is available where you shop, check whether the contents seem resilient when you squeeze the bag.

Leave packaged spinach in its cellophane bag, or pack it loosely in a plastic bag and store in the refrigerator . Fresh spinach will keep for three to four days.

Your first priority is to get rid of the grit. Fresh spinach often has sand trapped in the leaves and stems, and spinach always requires careful washing. (Don't, however, wash spinach before storing it for any length of time: After a day or so, it will begin to wilt and decay.) Trim off any roots, separate the leaves, and drop them into a large bowl of lukewarm water; agitate them gently with your hands. Lift out the leaves, letting the sand and grit settle, then empty and refill the bowl and repeat the process until the leaves are clean. And although bagged spinach is often labeled "pre-washed," it still must be carefully rinsed to clean away sand and grit. Loose spinach usually has more stem on it than bagged spinach, but both need to be stemmed if the stems are not very thin and tender. Pinch off the stems and also the midribs (the part of the stem that extends into the leaf), if they are thick and tough. You can easily stem spinach by folding each leaf in half, vein-side out, and pulling up on the stem as you hold the folded leaf closed. To crisp spinach for salad, wash the leaves, then dry in a salad spinner or shake dry in a colander. Wrap the spinach in paper towels, place in a plastic bag, and refrigerate for no longer than a few hours. Spinach that is to be cooked need not be dried; in fact, there is usually just enough water clinging to freshly washed leaves so that they can be steamed without additional cooking liquid.