Celery is a nutrient-rich, low-calorie food. Two stalks of celery contain only 15 calories. Aside from its low calorie count, celery contains dietary fiber, vitamin K, and small amounts of vitamins A and C, calcium and iron. Although celery also contains some natural sodium, it’s still considered a low-sodium food. Celery also has antioxidant properties, which may help reduce the risk of some chronic conditions. Made up of almost 95% water, celery is a great snack to have on hand during warm summer months to help maintain hydration.