Onions

Onions are a member of the allium family that also include garlic, shallots, leeks, scallions and chives
Onions are loaded with nutrients - they are excellent sources of vitamin C, sulfur-containing compounds, flavonoids and phytochemicals as well as fiber, potassium and folate
A particularly valuable flavonoid in onions is quercetin, which has a host of health benefits
Onions are a rich source of prebiotics, which help boost digestive health
Red onions contain anthocyanins — special plant pigments in the flavonoid family that give red onions their rich color

Leeks, despite their mild flavor, are rich in beneficial phytonutrients found mainly in the green parts that most people discard. When cooking, since the green parts are less tender, first cook them for a few minutes before adding the more tender white parts
When chopping onions, first cut them in half and only partially remove the outer skin so that you will have something to hold on to when chopping which makes the task a little easier.
The more pungent the onion the better it is for you. Sweeter, milder and larger varieties have fewer health benefits than the more pungent ones
Like garlic, let onions and leeks sit for at least 10 minutes after cutting and before cooking
Scallions are not smaller verisions of onions, but they are a species unto themselves with health benefits that far exceed those of regular onions and like leeks the most beneficial part of the scallion is in the green parts
Unlike onions, leeks and scallions lose most of their nutrient benefits after a few days in the fridge - it is best to eat them as soon as possilbe
Shallots, which have a milder and more layered flavor than regular onions, are superstars of nutrition - they have six times more phytonutrients and twice as much quercetin than a typical onion - ounce for ounce
Don’t store onions with potatoes as this will hasten the spoilage of both