Maybe you need to keep an eye on your fructose intake, whether you have fructose malabsorption or have been diagnosed with hereditary fructose intolerance. In the case of hereditary fructose intolerance, it is a very serious condition, and all sources of fructose, including tomatoes, should be eliminated from your diet, as advised by your doctor. However, in the case of fructose malabsorption, small amounts of fructose might be tolerable. Most people with fructose malabsorption can tolerate a few slices of ripe tomatoes, but tomato sauce and tomato paste can be problematic and cause bloating, diarrhea, constipation, flatulence and cramps.
A half cup of fresh, ripe cherry tomatoes contains 2.9 grams of carbohydrates, of which 0.9 grams is fiber, 0.9 grams is glucose and 1.0 gram is fructose. A medium whole ripe tomato provides 4.8 grams of carbs, with 1.5 grams of fiber, 1.5 grams of glucose and 1.7 grams of fructose. If you have 1 cup of chopped tomato, the carb content corresponds to 7.0 grams per serving, with 2.2 grams of fiber, 2.3 grams of glucose and 2.5 grams of fructose. Unripe tomatoes tend to have more fructose, some of which is then converted into glucose as the tomato ripens.
A 6-ounce glass of tomato juice contains 7.7 grams of carbs, of which 0.7 grams is fiber, 2.5 grams is glucose and 2.8 grams is fructose. Keep in mind that if you buy a large bottle of tomato juice, you will need to measure out a 6-ounce serving.
Tomato sauce contains about 13.2 grams of total carbs per 1-cup serving, of which 3.7 grams is fiber, 5.7 grams is glucose and 4.1 grams is fructose. Always check the ingredient list because if the tomato sauce contains added sugar, such as regular sugar or high-fructose corn syrup, the fructose content can be higher.
A 6-ounce can of tomato paste contains 32.2 grams of carbs, with 7.0 grams of fiber, 9.8 grams of glucose and 9.9 grams of fructose. However, tomato paste is usually not consumed in large amounts. If you use a 6-ounce can in a recipe that yields 8 servings, your fructose intake from the tomato paste will be about 1.3 grams per serving. Because tomato paste is usually added to tomato soup or a tomato-based sauce, you will also need to consider the fructose content of these other ingredients to determine the fructose content of your meal.