Spinach is loaded with iron and folate, a B vitamin considered so important that it is now routinely added to flour. Folate not only prevents neural-tube defects in babies but also lowers blood levels of homocysteine, an amino acid that irritates blood vessels and is linked to heart disease. Just as impressive, spinach contains two phytochemicals, lutein and zeaxanthin, that seem to ward off macular degeneration, a leading cause of blindness. One cup of spinach contains just 41 calories and no fat, so you needn't worry about any unsightly bulges in your forearms or anywhere else. Kale, Swiss chard and collard greens have the same health benefits of spinach.