Animal Fats Promote Tumor Growth in Obese Mice While Plant Fats Do Not

A recent comprehensive study published in Nature Metabolism has shed light on how different types of dietary fats influence tumor progression in obesity. Led by Lydia Lynch from Ludwig Princeton, the research investigated whether the increased cancer risk associated with obesity is primarily due to adiposity itself or specific dietary components. Over a decade, the team fed obese mice diets enriched with various fats, including animal fats like lard, butter, and beef tallow, and plant-based fats such as coconut, palm, and olive oils. The findings revealed that diets based on animal fats significantly weaken the immune system's ability to fight tumors, thereby accelerating tumor growth across multiple models. Conversely, diets rich in plant fats had less detrimental effects; notably, palm oil even enhanced anti-tumor immunity, reducing tumor progression in obese mice. The study further explored the mechanisms behind these effects, identifying metabolic byproducts of animal fats—especially long-chain acylcarnitines—that impair immune cells (natural killer cells and cytotoxic T lymphocytes). These metabolites disrupt mitochondrial function within immune cells, weakening their ability to attack cancer cells. Interestingly, palm oil seemed to bolster immune function by activating the c-Myc pathway, which supports cellular metabolism. The implications of this research are significant for cancer prevention and treatment strategies, suggesting that replacing animal fats with plant fats could improve immune responses in obese individuals undergoing cancer therapy. This research underscores the importance of diet quality, particularly fat sources, in maintaining immune health and reducing cancer risk in populations affected by obesity.