HOW MUCH: 1 cup Beets are rich in nitrate, which is converted in your body to nitric oxide (NO). NO can help increase blood flow by dilating arteries, aiding endurance and strength. (For natural supps that help boost strength, turn to page 94.) A study in the Journal of Applied Physiology found that subjects who took beetroot juice showed a 16% improvement in time to exhaustion on a cycling test. Because you need to eat a lot of beets to get the benefits, juice may be your best option.