Cabbage can taste bitter because tearing or cutting the leaves ruptures the cell walls that release oils containing sulfur compounds and gaseous oils. They are made from mustard oil and are a natural repellent to keep pests from eating them. Add one teaspoon of sugar and a teaspoon of salt for every two cups of cabbage. This brings on osmosis, which balances out the bitterness. You can also use honey, lemon juice, or vinegar.