Omega fatty acids are widely taken as healthy supplements — but a new mouse study suggests very high levels of them might, in some contexts, weaken a key cancer-fighting immune cell. It’s an early finding, and not a reason to change your diet.
Researchers at Yale University School of Medicine found that omega polyunsaturated fatty acids (PUFAs) — including omega-3 and omega-6 — can suppress the tumor-killing ability of natural killer (NK) cells, a front-line part of the immune system. The fats enter NK cells through a receptor called LRP5 and dial down the metabolic pathways (mTORC1 signaling and glycolysis) that NK cells need to attack tumors. The work was published August 12, 2026 in Science Signaling.
What they saw in mice
When the researchers deleted the LRP5 receptor, NK cells became better at eliminating colon-cancer cells, and mice on a PUFA-free diet had slower tumor growth. That suggests LRP5 acts like an “immune checkpoint” that restrains NK cells — a potential future drug target to boost cancer immunotherapy.
Important context
This is early, mouse-based research, not evidence that fish-oil supplements cause cancer or that anyone should stop taking them — omega fatty acids have well-documented benefits. First author Yi Luan simply noted that “greater public awareness of their potential unintended effects is warranted” given how heavily supplements are promoted. The real promise here is scientific: targeting LRP5 might one day strengthen the immune system against cancer.
This article describes early animal research and is not dietary or medical advice. Do not change your supplement use based on it; consult a healthcare professional about your diet.