Onions

Onions are such an everyday food that it's easy to overlook how much they offer. They're one of the richest sources of quercetin, a plant compound with antioxidant properties that's linked with healthy immune and heart function. They also contain prebiotic fibers, which feed the friendly bacteria in your gut, plus the sulfur compounds that make your eyes water.

To get the most from them:

• Choose red and yellow onions for the most antioxidants
• Peel off only the papery skin, since the outer layers are richest in nutrients
• Enjoy them both raw and cooked

If you have IBS, onions may be a trigger, so notice how they sit with you.

Try this: add thinly sliced red onion to tonight's salad, or quick-pickle a jar with vinegar and a pinch of salt.