What can I do myself to lower my risk of cancer?

Roughly 40% of all cancer cases are linked to factors you can influence yourself. That is the most useful starting point: not as a guarantee, but as a guide to where action pays off the most.

The three heaviest levers are smoking, excess weight, and alcohol, in that order of impact. Smoking is by far the largest, responsible for approximately 19% of all cancer cases in the US. Excess weight increases the risk of at least 13 types of cancer and contributes to around 7.6% of cases. Alcohol carries a genuinely elevated risk even at moderate consumption, accounting for more than 4% of cancer cases worldwide. If you want to focus on one thing, stop smoking, and if you do smoke, that is the most impactful step you can take. Alcohol has no safe lower limit when it comes to cancer, although the absolute risk at one drink per day is small for most people.

In addition, regular exercise and limiting UV exposure are proven to be effective, albeit with a somewhat smaller contribution to the overall picture. The link between physical inactivity and cancer is well established, particularly for colorectal and breast cancer. UV radiation is the dominant cause of skin cancer and the only risk on that list that you can almost entirely shield yourself from, through clothing, shade, and sunscreen.

Studies of people who combine the full package, meaning a healthy weight, sufficient exercise, low alcohol intake, and a diet rich in vegetables, fiber, and legumes and low in processed meat, consistently show lower cancer risks. The combination demonstrably works better than individual measures taken in isolation. The evidence is observational and other factors are always at play, but the direction is consistent enough across all major cancer types that it is worth turning several dials at the same time.