Cancer remains a major public health concern, with the number of cancer cases worldwide estimated to reach 28.4 million by 2040. Lifestyle factors, including smoking, physical activity, diet, alcohol consumption and body mass index (BMI), have been identified as important modifiable risk factors for cancer.

But could 5 everyday habits be linked to cancer risk?

A large new study published in the British Journal of Cancer analysed data from 287,745 people and found that participants who met 4 or 5 criteria for a healthier lifestyle had a lower risk of 13 of the 27 cancer types examined, compared with those who met only 0 or 1 criterion.

However, this was a prospective observational cohort study, not a randomised clinical trial. This means the findings show associations; they do not prove that following all five habits will necessarily prevent cancer.

What did the researchers investigate?

The researchers used data from the UK Biobank and followed 287,745 adults for a median of 11.5 years.

Each participant received a lifestyle score ranging from 0 to 5, depending on how many of five healthy lifestyle criteria they met.

For each participant, the researchers assessed:

  1. Smoking: participants had either never smoked regularly or, if they were former smokers, had a smoking history of less than 30 pack-years — for example, less than one pack of cigarettes per day for 30 years.
  2. Alcohol consumption within the limits defined by the study: up to 12 g of alcohol per day for women and up to 24 g per day for men.
  3. Diet: participants with the highest scores on the study’s diet quality index — specifically, those in the top 40% — received one point toward their overall healthy lifestyle score.
  4. Adequate physical activity
  5. BMI between 18.5 and 25 kg/m²

What did the results show?

During the follow-up period, 12,947 participants were diagnosed with cancer.

People with a high healthy lifestyle score — meaning they met 4 or 5 of the 5 criteria defined by the researchers — had an overall hazard ratio (HR) of 0.71 for developing cancer compared with those who met only 0 or 1 criterion.

This corresponds to an approximately 29% lower relative risk of developing cancer overall in the group with the healthiest lifestyle score. However, this does not mean that every individual would experience a 29% reduction in their personal cancer risk.

Which cancers were associated with a lower risk?

A higher healthy lifestyle score was associated with a lower risk of 13 types of cancer:

  • Oral cancer
  • Pharyngeal and laryngeal cancers
  • Oesophageal and stomach cancers
  • Colorectal cancer
  • Liver and pancreatic cancers
  • Lung cancer
  • Kidney cancer
  • Bladder cancer
  • Soft-tissue sarcoma
  • Postmenopausal breast cancer

Which factor appeared to matter most?

Among the five lifestyle factors examined, smoking stood out the most.

Not smoking was associated with a lower risk of 12 of the 27 cancer types studied, with particularly strong associations observed for lung, laryngeal, and pharyngeal cancers.

The authors concluded that, within the context of this study, smoking and excess body weight were the lifestyle factors most frequently associated with the cancer types investigated.

What does the study not prove?

The study does not prove that these five behaviours directly caused the observed reduction in cancer risk.

This was a prospective observational cohort study, not a randomised clinical trial. This means that other differences between participants may also have influenced the results.

Limitations reported by the researchers

  • The participants were not fully representative of the general population. This means we cannot assume that the findings apply in exactly the same way to everyone.
  • Most participants were White. As a result, it remains uncertain whether the same findings would apply equally to other population groups.
  • People who volunteer for studies like this are often healthier than the general population. They may pay more attention to their health or undergo health checks more frequently.
  • Much of the information was self-reported by participants. Some people may therefore have misremembered or underestimated behaviours such as how much they drank, smoked or exercised.
  • Other factors may also have influenced the results. Even with statistical adjustments, it is impossible to perfectly account for every difference between the groups.
  • Participants’ habits may have changed over time. Someone may have stopped smoking, gained weight or started exercising after their lifestyle was initially recorded.
  • There were relatively few cases of some rare cancers. This means the findings for these cancer types are less certain.