Vitamin C, also called ascorbic acid, is an essential nutrient because people cannot manufacture it. Citrus fruits are excellent sources of vitamin C, although other types of fruit such as guava, kiwi and papaya contain more of it per gram the citrus fruits such as oranges, grapefruits, lemons, limes and even tomatoes. Consume citrus fruits while they are fresh to ensure that you get the most vitamin C because the nutrient is sensitive to processing and degrades quickly.
Vitamin C is necessary to synthesize and maintain collagen, an elastic-like compound found in skin, ligaments, blood vessels, muscle tissues and bones. Vitamin C is also a powerful antioxidant that is able to reduce oxidation damage caused by free radicals. It’s an antimicrobial that can fight mild infections and an immune system booster. The current recommended daily amount of vitamin C for adults ranges from 75 to 125 milligrams, depending on gender, pregnancy, lactation and whether you smoke cigarettes. The amount of vitamin C in fruit is variable and depends on growing conditions, ripeness and varieties.
Oranges are the citrus fruit that contain the most vitamin C per gram. For example, oranges typically contain a little more than 50 milligrams of vitamin C per 100 grams of flesh, which equates to about 70 milligrams of the vitamin in a medium-sized orange. If you squeeze your own orange juice, drink it within a few hours because exposing the juice to air causes the vitamin to degrade. High heat, especially from pasteurization, is very destructive to vitamin C.
Lemons are regarded by most nutritionists as containing the second-highest amount of vitamin C per gram of fruit, but it depends on the factors discussed previously. Lemons contain about 40 milligrams of vitamin C per 100 grams of flesh, which equates to about 25 milligrams of the vitamin in a medium-sized lemon. Lemons -- due to their sourness -- are not eaten nearly as much as oranges, but lemon juice is commonly added to salads or used on fish and poultry.
Some nutritionists consider grapefruit to be the second-best source of vitamin C among citrus fruits, while others list it as third, but it depends on the soil in which the fruit is grown and the time between picking and testing. Grapefruits contain about 35 milligrams of vitamin C per 100 grams of flesh, which equates to almost 50 milligrams of the vitamin in a medium-sized grapefruit. Grapefruits are usually tarter and less sour than lemons, which is why they are commonly eaten for breakfast.
Limes and Tomatoes
Limes are also a good source of vitamin C, but they fall behind grapefruits. On average, limes contain a little less than 30 milligrams of vitamin C per 100 grams of flesh, which equates to about 8 milligrams of the vitamin in a medium-sized lime. Limes are sweeter than lemons and grapefruits, which is probably why they are used more often to garnish drinks and marinate fish and poultry.
Tomatoes are a good source of vitamin C but rank last among citrus fruits. On average, tomatoes contain a little less than 20 milligrams of vitamin C per 100 grams of flesh. Tomatoes may be the most versatile citrus fruit because they are used in so many different ways.
- Human Metabolism: Functional Diversity and Integration; J. Ramsey Bronk
- Contemporary Nutrition: Functional Approach; Gordon M. Wardlaw et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.