Sugars produced by gut bacteria trigger immune responses that cause amyotrophic lateral sclerosis (ALS).

Caveats

• The sole source linking bacterial sugars to cell-killing immune responses (Case Western Reserve University) is a press release about preliminary research, not a peer-reviewed study establishing causation in human ALS.
• Peer-reviewed evidence explicitly states that clinical causality between gut microbiota changes and ALS has not been established, and reverse causation—where ALS itself alters the microbiome—remains plausible.
• ALS is a multifactorial disease involving genetic factors (e.g., C9ORF72 mutations) and multiple environmental contributors; no single mechanism such as bacterial sugars has been validated as a cause.