Does consuming seafood cause the form of cancer called leukemia? No, that's not true: No scientific proof exists that eating seafood causes leukemia, a University of California, Riverside expert, who specializes in the study of how environmental factors cause cancer, told Lead Stories. The Mayo Clinic, a leading medical research institution, does not name seafood as one of the possible causes of leukemia, which still has no confirmed cause. A national cancer-care network, the City of Hope, in fact, encourages cancer patients to consume seafood for its health benefits.
The claim appeared as a video (archived here) posted on Facebook on March 14, 2023. It opened:
Stop eating seafood. Seafood causes cancer chemicals leukemia.
This is what the post looked like on Facebook at the time of the writing of this fact check:
(Source: Facebook screenshot taken on Thu Mar 16 20:38:43 2023 UTC)
The video shows an unidentified man speaking into the camera. It opens with the man saying, "Seafood causes cancer chemicals leukemia." The video bears a graphic that urges viewers, "Stop eating seafood."
The video narrator does not identify himself nor does he give any medical or scientific credentials that would add credibility to his claims. He offers no evidence to support any of his claims and cites no studies or medical research in his video.
While he blames a number of illnesses on seafood, this fact check will focus only on his claim that seafood causes leukemia.
Contrary to the video's claim, the Mayo Clinic reports that scientists still have not determined a cause for leukemia. The clinic adds that, "It seems to develop from a combination of genetic and environmental factors."
For further information, Lead Stories contacted David Eastmond, professor emeritus in the department of molecular, cell, & systems biology at the University of California, Riverside. He specializes in research into how chemicals cause cancer, including into the carcinogenic effects of exposure to benzene and formaldehyde, which are both associated with leukemia.
In a March 16, 2023, phone conversation, Eastmond told Lead Stories that no proof exists that eating seafood causes leukemia:
To my knowledge, there is no evidence that seafood causes leukemia. We do know a lot of different agents that cause leukemia, both chemical agents and radiation and viruses, but none of them are really present in seafood in any significant amount. So, I don't see any evidence to support that claim.
Eastmond explained that leukemia is "caused by genetic changes that occur in cells;" a process triggered by "different types of agents," one of which is "ionizing radiation." He cited the atomic bomb blasts in Hiroshima and Nagasaki, Japan in 1945, at the end of World War II, and noted an increase in leukemia among individuals who were exposed to the blasts' high level of radiation.
High levels of the widespread environmental chemical benzene, which is found in gasoline, tobacco smoke, and some air pollution, also can cause leukemia, Eastmond continued. Cigarette and tobacco smoking have been linked to the disease as well.
Certain medical conditions play a role, too, Eastmond said. Individuals with Down Syndrome are at a higher risk for leukemia, while the Associated Human T-Cell Lymphotropic Virus also has been associated with developing leukemias.
Seafood does not feature among the potential causes for leukemia listed by the Moffitt Cancer Center, a non-profit facility at the University of South Florida:
Risk factors that can cause leukemia
While the exact cause of leukemia--or any cancer, for that matter--is unknown, there are several risk factors that have been identified, such as radiation exposure, previous cancer treatment and being over the age of 65. With regard to the specific genetic and environmental factors that are thought to be linked to leukemia, and what causes bone marrow cells to mutate, researchers are evaluating certain combinations of:
- A genetic predisposition
- Down syndrome
- Human T-lymphotropic virus (HTLV)
- Human immunodeficiency virus (HIV)
- Exposure to petrochemicals, such as benzene
- Extensive exposure to artificial ionizing radiation
- Alkylating chemotherapy agents administered to treat other types of cancer
- Tobacco use
- Use of certain hair dyes
One national cancer-care network, the City of Hope, describes seafood as "an important part of a cancer patient's diet," if patients are able to eat it. A September 2022 article posted on the network's website advises:
[I]t's a good idea for patients [to] try to incorporate some fish into their diets, if they can, says Carolyn Lammersfeld, Vice President of Integrative Care at Cancer Treatment Centers of America® (CTCA). And you don't have to eat a lot of it to garner its benefits.
"A 3- to 4-oz. portion a couple times a week is good," Lammersfeld says. "That's probably all you need to get the health benefits."
The article, however, cites a Brown University study that found a connection between fish consumption and skin cancer, but concluded that, rather than the fish themselves, "our findings could possibly be attributed to contaminants in fish, such as polychlorinated biphenyls (PCBs), dioxins, arsenic and mercury." More study is needed, the researchers added.
A 2004 Canadian study, titled, "Dietary fish intake and risk of leukaemia, multiple myeloma, and non-Hodgkin lymphoma," found that:
After adjusting for age, sex, smoking, BMI, and proxy status, people who consumed greater proportions of their total energy intake from fresh fish had a significantly lower risk of each of the three types of cancer, and there was a significant dose-response for risk of leukemia and NHL.
The National Cancer Institute, part of the U.S. government's National Institutes of Health, reports that medical professionals, scientists and researchers see cancer as a subject area particularly prone to misinformation and disinformation.
Additional Lead Stories fact checks of claims about cancer can be found here.