Lemon juice is such a good source of both vitamin C and citric acid that you don’t need to consume a huge amount to get the antioxidant benefits. Citrus fruits are the only sources of flavanones, which add to the antioxidant impact of lemon juice. You can tell from the lip-puckering tartness of unsweetened lemon juice that it’s packed with acids. As a result, overconsumption puts you at risk for dental erosion and an upset gastrointestinal system.
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Health Benefits of Vitamin C
Like all citrus fruits, lemons are excellent sources of vitamin C. The juice from one lemon, which is a little more than an ounce and the amount often used to make 1 cup of lemonade, provides about 19 milligrams of vitamin C, according to the U.S. Department of Agriculture. Of course, you may get a little more or less, depending on the amount of lemon juice you consume, but it’s sure to make a good contribution to your recommended dietary allowance. Women should get 75 milligrams of vitamin C daily, while men need 90 milligrams.
Vitamin C is well known as an antioxidant that neutralizes reactive molecules -- free radicals -- before they damage tissues. As an antioxidant, vitamin C also protects molecules such as proteins, fats, carbs and DNA from damage by free radicals. Higher intakes of vitamin C are associated with a lower risk of cardiovascular disease. Your body also needs vitamin C to produce collagen, which is the connective tissue that supports and strengthens muscles, ligaments, skin and organs.
Citric Acid in Lemon Juice
Lemon juice contains more citric acid than other citrus fruits, according to a 2009 report in the Journal of Endourology. Citric acid is vital for energy production, but normally the body produces all it needs, so citric acid isn’t an essential nutrient. Citric acid from lemon juice still provides health benefits, however. When you consume lemon juice, the amount of citrate in urine increases, which naturally inhibits kidney stones from forming and also breaks down small stones that already exist. On the flip side, low levels of urinary citrate increase the risk of urinary crystallization and the development of kidney stones.
A study published in the Journal of Clinical Biochemistry and Nutrition in 2007 found that taking citric acid may reduce physical fatigue. Researchers had one group of healthy volunteers take citric acid, a second group received L-carnitine, and a third group got a placebo. After eight weeks, everyone exercised on stationary cycles under controlled conditions, then rated their fatigue. The participants taking citric acid were the only ones who felt less fatigued. Because this study included only 18 total participants, other people may not experience the same results. More research is needed to verify citric acid's role.
Citrus Bioflavonoids Provide Benefits
Lemons contain a group of plant-based flavonoids called flavanones. Like flavonoids found in other fruits and vegetables, the flavanones in lemon juice -- hesperetin, naringenin and eriodictyol -- function as antioxidants and help fight inflammation. Hesperetin shows promise for preventing cancer by inhibiting tumor growth. It may also help treat diabetes and reduce the risk of cardiovascular disease by lowering high blood pressure and blood levels of lipids, according to a review published in Life Sciences in March 2015.
Citrus fruits are the exclusive sources of flavanones, which is why you may also see them referred to as citrus bioflavonoids. Fresh lemon juice is unique among the other citrus juices because it has the potential to have the lowest and the highest amount of flavanones, with a range of 2 to 175 milligrams per 100 milliliters, or 3.5 ounces. For comparison, fresh orange juice has 5 to 47 milligrams. The wide range is due to differences in storage, preparation and processing, which may cause loss of flavanones.
Dangers of Excessive Lemon Juice
The acids in lemon juice can cause gastrointestinal side effects. Acidic foods may worsen symptoms of gastrointestinal reflux disease, or GERD, and some people get an upset stomach when they consume too much ascorbic acid. The combination of citric acid and ascorbic acid gives lemon juice a pH rating of 2 to 2.6, on a scale where zero represents the most acidic substances and battery acid has a score of 1. The Minnesota Dental Association reports that tooth enamel begins to erode from foods or beverages with a pH of 4, so the acidity of lemon juice can harm your teeth. Protect your teeth by rinsing with water when you’re done drinking lemon juice. It also helps to hold off on brushing for at least an hour to avoid rubbing acids around on your teeth with the toothbrush.