Eating three or more portions of fish per week slashes the risk of bowel cancer, a new study suggests. The research, conducted by the University of Oxford and the International Agency for Research on Cancer, examined nearly 500,000 people over the course of 15 years. The study found that eating any kind of fish around 3 times a week led to a 12% decreased risk of bowel cancer compared to those who consumed about half a portion a week.