No, Cassava Does Not Cure Cancer; Raw Cassava Can Cause Cyanide Poisoning

Subscribe to our WhatsApp Channel

Few messages spread faster in Sri Lankan family WhatsApp groups than the promise of a cheap, natural cure for cancer, and for months one such message has moved through local feeds with unusual conviction. It urges cancer patients, even children with brain tumours, to drink the strained juice of raw cassava (manioc) and to raise the dose each day until they feel dizzy, leaning on the authority of a Filipino professor said to have cured 500 patients and a Sri Lankan doctor said to have cured her own cancer the same way. Here are the posts that carried it.

Social Media Posts

The post first appeared on mainstream media websites, presented as an excerpt from a social media post, as follows:

“I am sharing this article in response to a request from a friend who sought an easy method of using cassava as a treatment for his relative’s daughter, who had developed a brain tumour. It concerns a professor who successfully used cassava as a treatment.

Professor Manuel Navarro of Santo Tomas University in Manila, Philippines, is reportedly said to have cured around 500 patients suffering from severe cancer using cassava treatment. The specific method used by Professor Navarro is given below.

Find a piece of fresh, clean raw cassava root about 4 inches long and 2–3 inches wide. Remove only its brown outer skin. Cut it into small pieces, place them in a blender, add two cups of boiled and cooled clean water, and blend at high speed for about two minutes. Pour the milky liquid into a tall glass and refrigerate for about two hours. The cassava starch will then settle at the bottom.

Carefully separate the clear, water-like liquid from the top into another container. Drink half before breakfast and the remainder in the evening. (The solution has a slightly bitter taste.) Repeat the preparation the following day, using a cassava piece half an inch longer than the previous day’s piece.

Continue increasing the cassava piece by half an inch each day and preparing and drinking the solution. At some point, you may feel dizzy after drinking it. (This is said to indicate the limit your body can tolerate.) From the following day, reduce the length of the cassava piece by half an inch. For example, if the piece that caused dizziness was 8 inches long, use a 7½-inch piece from the next day onward.

An important point is not to exceed your dosage and to follow it correctly. You may add orange or lime juice to improve the taste. Based on the experience of Dr. Cynthia Jayasuriya, this treatment is said to be followed for about three months. Dr. Jayasuriya reportedly stated that she completely cured her cancer by eating about 100 grams of cassava at each meal every day for three consecutive months.

Although Professor Navarro did not recommend this treatment for children, Cynthia Jayasuriya later stated that, based on practical experience, it could also be used for children, with a somewhat shorter initial cassava piece depending on the child’s age. Because the starch in cassava is removed, it is also claimed to be suitable for people with diabetes.

It is claimed that cassava and plants such as apricots contain Vitamin B17, which selectively destroys cancer cells without harming healthy cells. It is reported that 100 grams of cassava contains about 500 mg of Vitamin B17, while 100 grams of sweet potato contains about 100 mg. Vitamin B17 is also said to be found in red rice, red cowpeas and sesame, and anti-cancer potential is claimed for soursop, papaya, aloe vera gel, pomegranate and bitter melon seeds.”

Webpage  |  Archived Link

The same claim has also been circulating on social media for some time.

Facebook  |  Facebook   [PRODUCTION NOTE: these two near-identical posts could be merged]

We investigated the claim to determine whether it was true or false.

Fact-Check

We examined whether eating cassava or drinking raw cassava juice is medically proven to cure cancer or to have any positive anti-cancer effect. No such claim is supported by any recognized medical or clinical study worldwide.

Vitamin B17 is not a proven cancer cure, and it releases cyanide

Claims that cassava can cure cancer largely center on the assertion that it contains “Vitamin B17.” However, major scientific and health authorities, including the U.S. Food and Drug Administration (FDA), the American Cancer Society (ACS) and the World Health Organization (WHO), have found no evidence that B17 (amygdalin) cures cancer; amygdalin can instead cause serious cyanide poisoning.

Raw cassava contains the cyanogenic glycoside linamarin. Consuming raw cassava, particularly when blended and taken directly, can release cyanide in the body. The post’s claim that “dizziness indicates the dosage limit” is therefore highly misleading: dizziness can be an early sign of cyanide poisoning, which, if ignored, may lead to liver damage, neurological damage, severe illness, or death.

For further information, click here, here and here.

ScienceInsights also reports that there is no accepted medical evidence supporting Vitamin B17 (laetrile/amygdalin) as a cancer treatment, and that uncontrolled use may cause harm. Additional information is available from Cancer Research UK (Laetrile) and Memorial Sloan Kettering (Amygdalin).

The Agency for Toxic Substances and Disease Registry (ATSDR), under the U.S. Department of Health and Human Services, notes that certain plant-based foods, including cassava, naturally contain cyanide. High cyanide exposure can be fatal, while long-term reliance on cassava as a staple may damage the nervous system (impairing walking and vision) and lead to thyroid disorders. It may also affect unborn children through pregnant mothers. More information is available here.

The Navarro and Jayasuriya stories are personal claims, not medical proof

Professor Manuel D. Navarro was a physician who researched cancer during the 1950s–1970s and attempted to use “Laetrile” (the compound popularly known as Vitamin B17) as a cancer treatment. However, no scientific or clinical study has verified the recipe described in the post, which involves blending and drinking raw cassava juice. Although the post claims that Professor Navarro cured 500 cancer patients using cassava, no scientific or clinical evidence supporting this could be found. Extra information about Navarro is available here.

The post also claims that Dr. Cynthia Jayasuriya found relief from cancer by eating cassava. However, she was not an oncologist but a former Sri Lankan ear, nose and throat (ENT) specialist who claimed, in personal writings and statements, that her own cancer was cured by eating cassava. We found a mainstream media article reporting on these claims here; even that article presents the claim as her personal experience, not as a medically established discovery. As Dr. Jayasuriya is no longer alive, her account cannot be independently verified with her directly.

A consultant oncological surgeon warns against relying on cassava

Consultant Oncological Surgeon Dr. Nayomal Perera has released a video addressing social media claims that eating cassava can destroy cancer. In it, he notes that cassava contains minerals such as calcium, magnesium, and potassium, along with vitamins C, B1 (thiamine), B2 (riboflavin) and B3 (niacin). He gives particular attention to “Vitamin B17,” namely amygdalin or laetrile: an enzyme in cancer cells is said to release cyanide from this compound in an attempt to destroy the cancer cells, while healthy cells contain enzymes that detoxify the cyanide.

However, he notes that some patients try to use cassava instead of, or alongside, evidence-based treatments such as chemotherapy. He stresses that, despite strong claims that cassava can cure cancer, there is insufficient clinical or scientific evidence to support them. Abandoning established medical treatment and relying solely on such remedies is risky, and he advises seeking medical guidance before making any decision.

Sri Lanka’s National Cancer Control Programme confirms there is no evidence

We consulted specialists from the Ministry of Health’s National Cancer Control Programme for further clarification. They confirmed that no medical recommendation or scientific evidence currently supports cassava as a cure for cancer. Any new treatment must undergo rigorous research and evaluation before being accepted as medicine, and no such validation exists for cassava. While cassava may be a nutritious food, much like bitter melon for people with diabetes, it is not a cancer-curing medicine. The specialists noted that the claim has circulated for a long time and includes Dr. Cynthia Jayasuriya’s personal experience but stressed that this is only a personal account and that Jayasuriya was an ENT specialist, not an oncologist.

In Nigeria, Africa Check investigated a similar claim and consulted cancer specialist Professor Adeniyi Adenipekun, who confirmed that cassava neither cures cancer nor destroys cancer cells. He explained that cassava is a carbohydrate source converted into sugar after consumption; while all cells use glucose, sugar does not specifically accelerate cancer growth, and the greater concern is obesity and insulin-related factors. Read the full fact-check here.

Join Us

Join us to learn more about our fact-check investigations.

Facebook  |  Twitter  |  Instagram  |  Google News  |  TikTok

Conclusion

No recognized medical study supports eating or drinking cassava as a cancer treatment. Its cyanide content can cause poisoning at high levels, which makes the viral advice to “increase the dose until you feel dizzy” both misleading and dangerous, because dizziness can be an early sign of cyanide poisoning rather than a safe dosage limit.

This verdict is confirmed by the U.S. FDA, the American Cancer Society, and the WHO on Vitamin B17, by the U.S. ATSDR on cyanide in cassava, by Consultant Oncological Surgeon Dr. Nayomal Perera, by Sri Lanka’s National Cancer Control Programme, and by Africa Check’s review with a cancer specialist. Cassava is a food, not a cancer cure; experts recommend seeking effective, evidence-based medical treatment for cancer.