The highest concentrations of vitamin C are found in fruits and vegetables such as peppers and oranges, according to the National Institutes of Health. More vitamin C is available when these foods are consumed raw than when cooked.
The highest concentrations of vitamin C per serving are found in red peppers and orange juice, reports NIH. A half-cup of sweet red peppers contains 95 milligrams of vitamin C, while 3/4 cup of orange juice contains 93 milligrams. A medium-size orange and 3/4 cup of grapefruit juice both contain 70 milligrams. Kiwifruit and green peppers also have high concentrations of vitamin C. All of these foods contain 100 percent or more of the daily value of vitamin C, as established by the Food and Drug Administration. Foods containing more than 20 percent of the daily value are considered high sources of vitamin C. Other foods high in vitamin C include broccoli, Brussels sprouts, cantaloupe and strawberries.
More vitamin C can be obtained when these foods are consumed raw, because ascorbic acid is water soluble and destroyed when cooked at high temperatures. Loss of vitamin C is minimized by steaming or microwaving, states NIH. Prolonged storage also reduces the available amount of vitamin C in fruits and vegetables.