A cup of raw rhubarb has 26 calories, zero fat and cholesterol, 5 milligrams of sodium, 6 grams of carbohydrates and 1 gram of protein, according to Self Nutrition Data.
The same cup of raw rhubarb has 2 percent of the recommended daily allowance of vitamin A, 16 percent of vitamin C, 10 percent of calcium and 1 percent of iron. There is 9 percent of the recommended daily allowance of dietary fiber, at 2 grams. There are 1 gram of sugars and 2 calories from fat. Raw rhubarb is also a source of magnesium, manganese, vitamin K and potassium.