Rough guide - Fruit & vegetable portion sizes. FRUIT - Adult portion size = 80g. Fruit. Adult portion size examples - approximately equivalent to 80g in weight. (As eaten 20 raspberries. Rhubarb: canned however much you eat. This is. Nutrition facts and Information for Rhubarb, raw. Calorie Information. Amounts Per Selected Serving. %DV. Calories. ( kJ). 1%. From Carbohydrate. Rhubarb is a vegetable, but it is often cooked, sweetened and It does contain potassium and a small amount of vitamin C and fiber, two grams per cup. jams, cakes, muffins and combined with other fruits in baked sauces.