Fish oil makes breast cancer tumors in mice produce less of an enzyme that protects them from oxidative damage, and this makes the cancer cells more vulnerable to chemotherapy.

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Evidence from Studies

Supporting (1)

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Role of lipid peroxidation and antioxidant enzymes in omega 3 fatty acids induced suppression of breast cancer xenograft growth in mice

Cohort Study

Animal

2002 Jul 17

The study found that feeding mice fish oil lowered a specific enzyme (GPX) in breast tumors, and this drop made the tumors more sensitive to chemotherapy — which is exactly what the claim says.

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No contradicting evidence found

Source Study

Role of lipid peroxidation and antioxidant enzymes in omega 3 fatty acids induced suppression of breast cancer xenograft growth in mice

Score: 14

DOI: 10.1186/1475-2867-2-10

Similar Assertions

Fish oil and chemo together cause more oxidative damage in tumors than either alone, but that’s not the whole reason the tumors shrink — something else (like GPX suppression) matters more.

81%

Feeding mice a diet rich in fish oil changes the fat composition in their breast tumors, and those tumors grow slower when treated with a common cancer drug.

79%

Even when given an antioxidant (vitamin E), tumors in fish oil-fed mice still get more oxidative damage after chemo, meaning they’re already under more stress and can’t recover.

72%