Diet and Cancer
The American Cancer Society (ACS), World Cancer Research Fund, and American Institute for Cancer Research recommend several lifestyle choices, including:
- being as lean as possible without becoming underweight;
- being physically active for at least 30 minutes per day;
- eating a mostly plant-based diet;
- limiting red meats (beef, pork, lamb) and avoiding processed meats;
- limiting alcoholic drinks; and
- not taking supplements to protect against cancer.
Many of these recommendations are based on observational studies rather than by actual randomised trials.
High intake of red and processed meat has been found to be associated with increased risk of death. A US obserservational study (NIH-AARP Diet and Health Study) of about 600,000 individuals showed that the group that ate the most red and processed meat had a modest increase in cancer death, about 10 to 20% more than the group that ate the least amount of red and processed meats.
An analysis of nearly 450,000 individuals from 10 European countries (European Prospective Investigation Into Cancer and Nutrition) showed that consuming more red meat was associated with higher risk of death from all causes. Taking into consideration other factors such as smoking, body mass index and alcohol intake, the risk of cancer death was about 14% higher in the group consuming at least 160g red meat per day compared to the group consuming 10 to 20g red meat per day. The association with processed meat was higher than for red meat (about 44% more deaths from cancer in the group consuming 160g processed meat compared to the group consuming 10 to 20g processed meat daily).
Alcohol drinking, more than five drinks per day, has been linked very strongly to 11 different cancers: oral, pharyngeal and laryngeal, esophageal, breast, colorectal, liver, stomach, gall bladder, pancreatic, and lung. One drink is about:
- 300ml beer or cider,
- 150ml wine or
- 40ml brandy, whiskey, gin, vodka, rum, etc.
Available data support not taking vitamin supplements to prevent cancer. VITAL (VITamins And Lifestyle) was a study of men and women aged 50 to 76 years living in Washington State in the USA. 364,400 questionnaires with a list of brand name vitamins and supplements were mailed out and 79,300 questionnaires were returned. Respondents were asked how many of the brand name vitamins and supplements were taken over a 10-year period. Respondents were followed up to determine how many developed cancer. 56% of respondents were never smokers.
It was found that using beta-carotene supplements for more than 4 years was associated with an 18% higher risk of lung cancer. Longer duration of retinol (a type of Vitamin A) supplements was associated with 53% more lung cancer, worse for men than for women. Lutein supplements were associated with 102% more lung cancer, worse for women than for men.