Does cancer mean your immune system failed? It's more complicated

Claim

CANCER AND YOUR IMMUNITY

Catch

A LINK, NOT A CAUSE

Verdict

IMMUNITY MATTERS, SO DOES SCREENING

Natural killer (NK) cells are immune cells that can find and destroy abnormal cells, including some cancer cells. In a Japanese study of 3,625 people followed for 11 years, those with high NK cell activity had about 37% lower cancer risk than those with low activity. Gut bacteria matter too: in cancer patients on PD-1 immunotherapy, gut microbes affected how well the drugs worked, and antibiotics reduced the benefit. The catch: these are links, not proof that a weak immune system or gut causes cancer. Cancer is driven mainly by gene mutations, and no gut cleanse has been shown to prevent it.

SOURCES

1. Imai et al. (2000), "Natural cytotoxic activity of peripheral-blood lymphocytes and cancer incidence: an 11-year follow-up study of a general population," The Lancet
2. Routy et al. (2018), "Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors," Science

For information only, not medical advice. Follow your doctor's screening schedule.