# The Blastocystis-colorectal cancer hypothesis: correlation is not causation

## TL;DR

This paper argues that the link between Blastocystis and colorectal cancer is not supported by strong evidence and warns against drawing premature conclusions.

## Contribution

The paper challenges the hypothesis that Blastocystis causes colorectal cancer due to lack of robust evidence.

## Key findings

- Blastocystis is commonly found in human populations, so its presence in CRC patients is expected and not proof of causation.
- Current claims linking Blastocystis to CRC are based on weak correlations and a poorly controlled study.
- The authors emphasize the need for rigorous research before concluding any microbial causation in disease.

## Abstract

Although superficially persuasive, claims suggesting a causal link between
Blastocystis and colorectal cancer (CRC) lack robust scientific support. As
Blastocystis is the most common gut protist found in human populations globally, its detection in CRC patients is unsurprising and does not imply pathogenicity. Current claims championing a causal role for
Blastocystis in CRC are based on speculative correlations, a single poorly controlled animal study, and inconsistent subtype associations. We argue that linking
Blastocystis to CRC is premature, misleading, and may give rise to unnecessary concern in patients that are colonised by or test positive for
Blastocystis. We emphasise the need for rigorously designed investigations to establish causal roles for any microorganism in disease and the importance of conclusions being based on solid evidence, particularly in matters of public health.