Acid Found in Lemons & Limes

If you've ever cut yourself and then accidentally exposed the wound to lemon or lime juice, you know how acidic these fruits are. In fact, of all citrus fruits, lemons and limes have the highest citric acid content -- about 1.4 grams per ounce, or about 8 percent of their dry weight. Lemons and limes also contain ascorbic acid, or vitamin C, an essential nutrient you need in your diet, and malic acid.

Citric acid is a weak organic acid that is found in concentrated amounts in citrus fruits, especially lemons and limes. Citric acid from lemons and limes is often used as an additive in food preparation, both to add a tart flavor and as a preservative. For example, citric acid helps prevent browning of fresh vegetables and maintains the color of meat during storage. It also prevents the crystallization of sucrose in candy and promotes flexibility and separation of cheese slices.

Citric acid is not a necessary part of the human diet, but it may have a role to play in your health. According to the UW Hospital Metabolic Stone Clinic, it can be beneficial for people who have kidney stones because it inhibits their formation and helps break up stones that are starting to form. A study published in Journal of Biochemistry and Clinical Nutrition in November 2007 suggests that citric acid can help reduce physical fatigue. Study participants were given either a citric acid supplement or placebo and made to perform a strenuous physical task. Physiological stress markers were lower in the citric acid group, as was the subjective feeling of fatigue reported by participants.

Better known as vitamin C, ascorbic acid is the second type of acid found in lemons and limes in rich supply. The juice of one lemon provides almost 20 milligrams of vitamin C, which is 30 percent of the daily value. The juice of one lime provides about 13 milligrams, or a little more than 20 percent of DV. Gram-for-gram, lemons and limes are as good a source of vitamin C, but not as good a source as oranges.

Unlike citric acid, vitamin C is an essential nutrient, meaning you need it in order to function properly and survive. Vitamin C's main functions include forming a crucial protein that is used to make skin, tendons, ligaments and blood vessels; helping wounds heal and scar tissue form; and repairing and maintaining cartilage, bones and teeth. Vitamin C is also an important antioxidant, a nutrient that prevents damage to your body by free radicals. Free radicals are formed by your body during the metabolism of food and when you are exposed to pollutants such as cigarette smoke, and they contribute to the aging process and the development of cancer, heart disease and arthritis.

Lemons also contain a small amount of malic acid, which is tart but enhances the sweetness of sucrose in fruit, according to an article published in the Journal of Experimental Botany in March 2006. The body also produces malic acid. According to NYU Langone Medical Center, malic acid may have therapeutic benefits for individuals with fibromyalgia, a condition that causes pain and tenderness throughout the soft tissues of the body. People with fibromyalgia may have trouble using or producing malic acid, which can affect normal muscle function. NYU Langone states that evidence is preliminary and further studies are needed.