A recent systematic review found that people who consumed more cruciferous vegetables, such as broccoli, cabbage, cauliflower or Brussels sprouts, had a 20% lower risk of colon cancer compared to those who consumed less.
The researchers analyzed data from over 17 studies, comprising a total participant pool of 639,539, with 97,595 cases of colon cancer. Including 20–40 grams of cruciferous veggies has the best protective effect per gram.
The study is published in BMC Gastroenterology.
Apart from being a rich source of beneficial phytochemicals, including flavonoids, fiber, vitamin C, and carotenoids, cruciferous vegetables are also packed with glucosinolates. When chewed, these compounds break down into bioactive isothiocyanates, particularly sulforaphane (SFN)—a molecule responsible not only for the vegetables’ strong, distinct odor but also for their protective, chemopreventive effects.
Isothiocyanates exhibit their cancer-protective role through multiple mechanisms: they can block enzymes that activate carcinogens, trigger apoptosis (programmed cell death) in malignant cells, inhibit the formation of new blood vessels at tumor sites, and arrest the cell cycle, thereby preventing uncontrolled growth of cancer cells.
The researchers analyzed data from seven cohorts and 10 case–control studies to explore the dose–response relationship and determine whether higher vegetable intake corresponded to a greater reduction in risk, and, if so, the specific amounts at which this effect became significant.
They found that the sweet spot where the protective effect of eating the veggies started to appear was at around 20 grams a day.
The greatest risk reduction per gram was observed between 20 and 40 grams, but no significant improvement was seen beyond 40 grams per day. The protective effect plateaued between 40 and 60 grams, with no additional benefits above this range.
The study also revealed that geography may play a role in determining the extent of the protective effect.
The team found that the protective effect was particularly noticeable in studies from North America and Asia, but less clear in Europe or Australia.
The researchers note that while this study suggests a promising inverse relationship between higher intake of cruciferous vegetables and colon cancer incidence, the findings should be interpreted with caution.
