Full Fact has identified a Facebook post claiming various health benefits from consuming lemons, including that the fruit has “the miraculous ability to kill cancer cells! It is 10,000 times stronger than chemotherapy!!”.
While lemons have beneficial compounds that some studies suggest may extend to fighting cancer, they are not a proven cure for all cancers, and there’s no evidence they are substantially more effective than chemotherapy.
A very similar message spread through WhatsApp in India earlier this year, falsely claimed to be written by a leading doctor, and was fact checked by an expert from India’s Adyar Cancer Institute.
Similar claims about lemons having better anti-cancer properties than chemotherapy were also fact checked by Snopes in 2011, the USA-based National Centre for Health Research and the University of Arkansas for Medical Sciences.
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Lemons contain compounds beneficial for human health
Lemons and their peels contain many beneficial substances such as vitamin C and flavonoids (a group of substances found in plants that may have disease-fighting actions). These substances have been proposed as anti-cancer agents, both in preventing cancer developing and treating it once it has.
A review of five studies found that consumption of citrus fruits was associated with a 13% reduction in the risk of stomach cancer over a time period of 4.5 to 11 years.
The studies did not all use lemons, and there are issues with confounding (where not all other differences between the groups have been controlled for) but it shows the potential for eating a diet high in citrus fruits to slightly reduce the risk of developing stomach cancer specifically.
Eating lemons is not proven to treat cancer
Taking vitamin C supplements is generally considered to have little benefit for people with cancer, and there are some potential risks. A small trial raised the possibility of supplements improving chemotherapy effectiveness for patients with specific blood cancers who were also deficient in vitamin C, but the study itself notes that it was not conclusive. Two older studies in the reputable New England Journal of Medicine showed no positive effects from high dose vitamin C supplements in patients with advanced cancers.
Recent studies have shown potential for benefit of intravenous (IV) vitamin C alongside conventional chemotherapy in improving symptoms, and even some evidence that it could have anti-cancer action of its own against specific cancers. This means that IV vitamin C is an area for future research.
But this research does not support the claims made in the post, because the quantities used in the studies cited were much larger than the intake from eating lemons. Eating them also involves taking in vitamin C orally, not intravenously, which, as mentioned, has much less evidence for being useful for people with cancer. A 2019 study showed that oil processed from lemon tree leaves and branches (not the fruits) was found to have some cytotoxic (cell killing) effects on breast cancer cells in vitro (outside of the human body). But the study notes that more thorough research is needed and that this tells us nothing about the safety or efficacy of using the oil in people.
The study treated other cells with a chemotherapy drug doxorubicin (another name for adriamycin, which is mentioned in the Facebook post), and found broadly similar results between the cells treated with the oil and the chemotherapeutic drug, contradicting the claim made in the post that “compounds of this tree showed 10,000 times better effect than the product Adriamycin”.
Anti-cancer properties have been found for concentrated flavonoids from citrus fruits, like lemons, in the lab setting both on their own and by using them alongside standard chemotherapy drugs. This means that the substances can have effects on cancer cells in a petri-dish, test tube or in rats or mice—but this does not necessarily mean that they work in people, and as of yet there is no evidence showing that they do.
The substances are also generally used at much higher doses than could reasonably be consumed by eating whole lemons, with manufactured extracts used rather than the fruits themselves.
More evidence is needed before claims can be made
All of this sets up the possibility for further research into these compounds, and the possibility that they or compounds related to them could be developed for fighting cancer at some point down the line. But there is no current evidence to suggest that lemons are “a proven remedy against cancers of all types”.
The post makes various other claims such as that lemons are on the “anti microbial spectrum” and can act “against bacterial infections and fungi[...] against internal parasites and worms”, that “it regulates blood pressure” and are “an antidepressant, combats stress & nervous disorders”. We have not looked specifically into these claims.
Image courtesy of SHVETS production