Lemon

Scientific Name(s): Citrus limon (L.) Burm. f. [medica × aurantifolia]
Common Name(s): Lemon

Botany

The lemon tree is an evergreen, growing to over 6 m in height. Its toothed leaves are light green and the citrus fruit (lemon) is oval, small, and green to yellow. Unlike other citrus varieties, the lemon tree bears fruit continuously. The plant is cultivated in Mediterranean and subtropical climates worldwide.1, 2, 3

History

The lemon originated in Southeast Asia, probably in India or southern China. Its history is sometimes unclear because of the confusion with the similarly appearing citron, a closely related species. The lemon may have been depicted in Roman artwork as early as the first century AD.3

In the 1600s, physicians became aware that daily intake of lemon juice would prevent outbreaks of scurvy among sailors on long sea voyages. English ships were required by law to carry enough lemon or lime juice for each sailor to get 1 ounce daily, earning them the nickname "limeys."4

The California lemon industry became established after the gold rush of 1849. From 1940 to 1965, production increased and the United States became a major provider of lemons. More than 50% of the US lemon crop is processed into juice and other drink products. The peel, pulp, and seeds are used to make oils, pectin, or other products.3

Lemon juice has long been used as an astringent, diaphoretic, diuretic, gargle, lotion, and tonic.3 Application of lemon juice in conjunction with exposure to sunlight was once thought to fade tattoos, but this theory was disproven.5 Lemon has also been used externally for acne, fungus (ringworm and athlete's foot), sunburn, and warts.2

Chemistry

Citrus fruits in general contain sugars, polysaccharides, organic acids, lipids, carotenoid (pigment), vitamins, minerals, flavonoids, bitter limonoids, and volatile components.6, 7 The lemon is a good source of potassium (145 mg per 100 g fruit), bioflavonoids, and vitamin C (40 to 50 mg per 100 g, twice as much as oranges).2, 3 The isolation of vitamin C from lemon juice has been performed.8 Calcium (61 mg) is also present, along with vitamins A, B₁, B₂, and B₃. The fruit is also low in calories, containing 27 Kcal per 100 g.2, 3, 9 Other constituents of lemon include volatile oil (2.5% of the peel), limonene, alpha-terpinene, alpha-pinene, citral, coumarins, mucilage, pectins, and bioflavonoids (mostly from pith and peel).2, 10, 11, 12, 13 Flavonoids eriocitrin and hesperidin have been evaluated.10, 14 When purchasing supplements for bioflavonoid benefits, note that content varies. Low-cost powdered lemon (and other citrus fruit) peel contains only 1% to 2% flavonoids; however, standardized products contain 10% to 90% flavonoids.15

Uses and Pharmacology

Pharmacologically, the lemon is primarily important for its vitamin C and potassium content. Epidemiological studies associate the intake of citrus fruit with a reduction in the risk of various diseases.13, 16, 17

Antioxidant effects

German studies in the late 1980s related this effect to the peel.4 The pectin fiber and lemon oil also possess antioxidant properties.18

Animal data

One group of researchers, having identified eriocitrin, hesperidin, and coumarins as antioxidants, pursued experiments in diabetic rats14 and venous endothelial cells10 as well as in activated Epstein-Barr virus models.11 Antioxidant mechanisms include the inhibition of radical formation and radical scavenging.10, 11, 13

Clinical data

Clinical trials are lacking.

Cancer

Animal data

In an experiment with the flavonoid eriocitrin and its metabolites19 and with coumarins extracted from lemon fruit11 apoptosis has been demonstrated in acute myelomonocytic leukemia cells.

Clinical data

Quality clinical studies are lacking. A meta-analysis of epidemiological studies associates the consumption of citrus fruit with a larger protective effect against oral cancer (odds ratio, 0.38; 95% confidence interval, 0.26 to 0.56) than with overall fruit consumption.17 The structure of various chemical constituents of lemon and their relationship to cancer prevention has been investigated.13, 20

Nephrolithiasis

Animal data

Studies have been conducted in rodents.21

Clinical data

Lemon juice has been shown to increase citrate levels in patients with hypocitraturic calcium nephrolithiasis in a small, long-term trial (mean duration, 44.4 months); 120 mL diluted lemon juice containing 5.9 g consumed daily resulted in a clinically important reduction in stone formation.22, 23 Few quality clinical trials are, however, available.24

Other uses

Lemon juice and lemon oil have been evaluated for antimicrobial action. The oil shows some bacteriostatic and antiviral action thought to be due to citral and linalool content.12, 13, 25 Lemon has been shown to inhibit the growth of Aspergillus mold26 and has been used to disinfect drinking water27 and to inactivate rabies virus.28 In cats, lemon essential oil has been shown to exert activity against Microsporum canis.29

The sperm-immobilizing properties of lemon juice have been investigated as a potential topical vaginal contraceptive.30 Lemon juice accelerated the transit of tetrofosmin through the liver parenchyma and improved myocardial imaging in a small study.31

A study in rodents reported increased bleeding and thrombin time with Citrus limon dosing, suggesting a cardioprotective role in preventing thrombosis.32

A variety of in vitro and rodent studies continue to be conducted, including the effect of Citrus limon peel extract on induced diarrhea33 and to combat obesity,34 as well as the effect of the essential oil on hepatotoxicity and nephrotoxicity induced by aspirin in rats.35

A nasal spray combination of lemon and quince was shown to possess antiallergic effects in a small clinical study (n=43).36

Dosing

Clinical information is limited. To increase citrate levels, 120 mL of lemon juice, containing citric acid 5.9 g, was diluted and consumed daily.22

Pregnancy / Lactation

Generally recognized as safe when used as food. Avoid dosages above those found in food because safety and efficacy are unproven.

Interactions

Chloroquine plasma concentrations may be reduced, decreasing the therapeutic effect.37 Lemon juice may increase iron absorption.26

A study in rodents reported increased bleeding and thrombin time with Citrus limon dosing. Interactions with concurrent anticoagulant medicines might be theorized.32

Adverse Reactions

Lemon juice may cause loss of gloss, alteration in enamel color, and irregular dental tissue on tooth enamel.38, 39, 40, 41

Anaphylactic allergy to lemon soap has been reported resulting from a possible cross sensitivity of citrus seed to peanut allergen.42

Citrus juice is often implicated in the worsening of gastroesophageal reflux disease symptoms. However, no effect on lower esophageal sphincter pressure was demonstrated in a small study, and the effects are not considered to be related to fruit juice acidity.43

Toxicology

Research reveals little or no information regarding toxicology with the use of lemon.

References

Disclaimer

This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

Copyright © 2018 Wolters Kluwer Health

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer