In a 2025 prospective study from Japan, patients who ate more vinegar-containing foods before starting immune checkpoint inhibitors (i.e. immunotherapy) had nearly twice the vinegar intake of non-responders and were significantly more likely to see their tumors shrink. It was a small study, Japanese patients only, it was observational but still interesting. Vinegar and vinegar containing foods may be an important missing ingredient in supporting the microbiome and optimizing immunity.
https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1640603/full
https://www.tiktok.com/@drlemmocancer/video/7675130010901957908