Around 1 in every 20 people in the U.S. is likely to develop bowel cancer over the course of their lifetime, notes a press release on the topic. Worldwide, over 2.2 million new cases and 1.1 million deaths due to bowel cancer are predicted every year by 2030.
It takes more than 15 years for bowel cancer to develop, so the press release explains that a healthy lifestyle may play a key role in helping pause or stop its progress.
Researchers for this analysis searched relevant research databases for published systematic reviews and meta-analyses of clinical trials and observational studies assessing the impact of dietary and medicinal factors on bowel cancer risk. Medicinal factors included aspirin, non-steroidal anti-inflammatory drugs such as paracetamol, and statins; dietary factors included vitamins, supplements, coffee, tea, fish and other fatty acids, dairy products, fiber, fruits and vegetables, meat, and alcohol.
They included studies published in French or English between September 1980 and June 2019, but excluded studies involving people at a high risk of developing bowel cancer.
Magnesium intake of at least 255 mg/day was associated with a 23% lower risk compared with the lowest intake; high intake of folic acid was associated with a 12-15% lower risk, although the press release explains that it wasn’t possible to pinpoint a threshold dose from the available data.
Similarly, dairy intake was associated with 13-19% lower risk of the disease, but there was a small number of available meta-analyses, different research outcomes, and a variety of dairy products included, making it difficult to draw firm conclusions about quantities required.
Fiber intake was associated with a 22-43% lower risk, while fruit and vegetable intake was associated with up to a 52% lower risk, with added benefit for every 100 g/day increase in intake.
Researchers also found that aspirin and NSAIDs were associated with a fall in incidence of bowel cancer.
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There was no evidence, however, that vitamins E, C, or multivitamins were protective against bowel cancer; no evidence was found for beta-carotene or selenium, either. There was minimal data on the impact of tea, garlic, onions, vitamin D, coffee, fish, or vitamins A or B.A negative effect was found with regards to meat, particularly red and processed meat—risk of bowel cancer increased with each additional 100 g/day of red meat eaten, raising risk between 10 and 30%.
The researchers noted that there was a low level of evidence for most of these conclusions, mainly due to wide differences in study design, end points, and number of participants, among other factors. And the researchers were unable to define optimal dosage and duration of intake for any of the products studied. However, they suggest that these findings could help clinicians advise patients on the best diet to lower bowel cancer risk, and could help guide future research.
