Lemons (Citrus limon) are a good source of vitamin C, eriocitrin, and naringenin. Lemons and lemon peel are also good sources of hesperetin and its glycoside hesperidin, limonene and its D isomer D-limonene, and D-limonene's metabolite perillyl alcohol, all of which have been reported to have anti-cancer properties.
Lemons have been shown to have antioxidant, anti-inflammatory and antimicrobial properties. Consumption of lemons and lemon juice may improve cholesterol profile and reduce blood pressure. Hesperidin has been shown to inhibit androgen-dependent prostate cancer cell growth and to have chemopreventive action against carcinogen-induced lung cancer in mice. Limonin has been shown to suppression colon carcinogenesis in rats. Lemon consumption has been found to be associated with lower risk of thyroid cancer.
Lemon peel contains the monoterpene D-limonene, which is metabolized into perillyl alcohol and some other components. D-limonene has been used in patients to dissolve cholesterol-containing gallstones and for the relief of heartburn and gastroesophageal reflux (GERD). D-limonene and its metabolites have also been shown to inhibit the growth of human leukemia and lung cancer cells in the laboratory, as well as opposing lymphoma and skin, stomach, pancreatic, colon, and liver cancer in animals. In addition, D-limonene has been shown to enhance the antitumor effect of the chemotherapy drug Taxotere (docetaxel) against prostate cancer cells without being toxic to normal prostate cells. Perillyl alcohol has been shown to inhibit androgen-induced prostate cancer cell growth and carcinogen-induced colon cancer in rats.
Consumption of lemon peel has been found to be associated with lower risk of squamous cell carcinoma of the skin. However, several studies have reported that people with diets high in citrus fruits appear to be at increased risk of malignant melanoma, possibly from ingesting psoralens, a type of photosensitizing compound found in citrus.

Breast cancer-related effects of eating lemons

No population studies have been performed that directly assess the association between consuming lemons or lemon rind and the risk of breast cancer. Hesperidin, limonene, and perillyl alcohol have all been shown to inhibit the proliferation of breast cancer cells in the laboratory. Lemon extract has been shown to induce apoptosis (programmed cell death) of hormone receptor positive (ER+/PR+) breast cancer cells. On the other hand, some of the chemopreventive compounds found in lemons or their components can interfere with the effectiveness of some breast cancer treatments, as explained in the sections below.

Hesperetin and hesperidin

Hesperetin is the parent flavanone of hesperidin. Hesperidin is found most abundantly in the peel, pith and membranous parts of lemons and other citrus fruits. Food sources include lemon zest, lemon tea, lemon marmalade, lemon peel extract, lemon peel oil and dishes that incorporate lemon zest or dried lemon peel. Lemon juice made by hand from lemons without a great deal of pressure on the peels does not contain significant levels of hesperidin. The higher pressures used to to make commercial lemon juice can greatly increase the fraction of hesperidin.
Hesperidin has been shown to reduce ER+/PR+ cell viability in a dose- and time-dependent manner and to inhibit ER+/PR+ cell proliferation, colony formation, and migration. Hesperetin has been shown to inhibit aromatization (the process by which androgens are converted into estrogens in the body) in a mouse model of ER+ breast cancer. Hesperetin has also been shown to act as an HER2 inhibitor, with antiproliferative, pro-apoptotic and other anti-cancerous activities against HER2+ breast cancer cells.
Pre-treatment with hesperidin before Adriamycin (doxorubicin) chemotherapy has been demonstrated to reduce tumor numbers and increase survival in a rat model of breast cancer. The same study also found that hesperidin helped protect against Adriamycin-induced toxicity in the vital organs of the animals, apparently by reducing inflammation.
Hesperidin can interfere with some breast cancer treatments
Hesperidin has the potential to interfere with chemotherapy regimens containing cyclophosphamide, which is an alkylating agent frequently used in combination with anthracyclines (Adriamycin, epirubicin) and/or taxanes (Taxol, Taxotere). Examples of such regimens include TAC (Taxotere, Adriamycin and cyclophosphamide), TEC (Taxotere, epirubicin, and cyclophosphamide) and FEC (5-fluorouracil, epirubicin and cyclophosphamide) chemotherapy.
While, as noted above, hesperidin has been shown to inhibit aromatase activity, paradoxically, it also has the potential to interfere with aromatase inhibitor treatment. Lemon peel and related products, as well as commercial lemon juice, should be avoided during chemotherapy that includes cyclophosphamide, and during aromatase inhibitor treatment.

Limonene

Limonene, a cyclic monoterpene, and its D isomer D-limonene, are found primarily in citrus peels. However, fresh lemonade has also been shown to be a good source of D-limonene. Limonene has been reported to have chemopreventive effects with respect to breast cancer, but the evidence is limited compared to that of other citrus micronutrients. One 2024 study reported that limonene enhanced cisplatin's cancer-inhibiting effects in triple negative (ER-/PR-/HER2-) breast cancer cells. Another study found that limonene could interfere with the effectiveness of Taxol.

Naringenin

While grapefruit is the most abundant source of naringenin, this flavanone is also found in lemons. Naringenin has been shown to inhibit metastasis in a mouse model of breast cancer. Naringenin also has cytotoxic activity against both ER+/PR+ and triple negative breast cancer cells.
Naringenin has been found to inhibit the proliferation of ER+/PR+ breast cancer cells by impairing glucose uptake. In addition, naringenin has been shown to inhibit ER+ breast cancer cell growth and migration in the presence of estradiol (E2). Like hesperetin, naringenin has been shown to act as an HER2 inhibitor, with antiproliferative, pro-apoptotic and other anti-cancerous activities against HER2+ breast cancer cells.
One study reported that combining the chemotherapy drug Adriamycin with naringenin and the anti-diabetes drug metformin resulted in lower tumor volume and weight compared to treatment with Adriamycin alone in a mouse model of triple negative breast cancer.

Vitamin C

High intakes of fruits and vegetables rich in vitamin C have been found to be associated with lower breast cancer risk. Vitamin C appears to act synergistically with other nutrients in the diet to oppose cancer. Vitamin C has been found to be cytotoxic against ER+/PR+ and triple negative breast cancer cells.

Additional comments

Non-organic lemons should be washed thoroughly before using mainly because of pesticides and other contaminants on the peels which will be in the zest and can be transferred to the flesh during cutting.
Limes (Citrus aurantifolia) are closely related to lemons, and have similar nutritional characteristics for the most part. However, limes have the potential for adverse drug interactions similar to grapefruit and should be avoided during all types of systemic treatment.

Sources of information provided in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list of studies, please click on lemon.