New study finds the type of dietary fat you eat could play a role in your anti-tumour immune response.

A new study published 25th July 2025 has taken a look at how adjusting our diet, more specifically the fats we eat, can affect the body’s typical immune response to tumours.

In a nutshell, the study found that high-fat diets derived from lard, beef tallow or butter accelerated tumour growth in a model based on melanoma in mice. The good news however, is that high-fat diets based on non-animal derived fats like coconut, palm or olive oil do not accelerate tumour growth, even when the mice are equally as obese.

The scientists that published the work highlight the importance of the findings, underlining the significance of our dietary choices and the effects that they could have on obesity-related cancer outcomes.

A butter-based high fat diet stood out as accelerating tumour growth, and impaired critical tumour-fighting cell types from doing their work. Researchers also noticed mice on the high butter diet started to build up and accumulate lipids - like cholesterol - within their cells, leading to reduced function of their metabolism.

It has been found in other studies that eating a diet high in plant based fats like olive oil prolonged the life of pancreatic cancer patients more than with high animal fat diets.

The main study however did acknowledge some limitations in its methods. Scientists used fats that were derived from single sources, and highlighted that this does not form a perfect parallel with a realistic human diet. The changes noticed in the study were not consistent across all tumour types either, adding to the complexity of the findings. These types of limitations are quite common with this type of study, so we should still recognize the study as an important early step into learnings that can guide our choices and behaviour, like switching to a plant-based fat diet.

If you'd like to take a look at the full study yourself, you can do that here.