Rhubarb stalks are a nutritious, low-calorie vegetable that are perfectly safe to eat. However, rhubarb leaves contain oxalic acid, which may cause kidney stones and oxalate poisoning. Even though you’d have to eat over 10 pounds of leaves to put your health at risk, why chance it? Eat the stalks and leave the leaves behind. If you’re craving greens, cook up some kale or chard.