5,774,010 people participated in the study.

Researchers conducted a meta-analysis of 226 observational studies, including 93 cohort studies and 133 case-control studies. The included studies were performed all over the globe, including in Japan, European countries, and the U.S.. The duration of the studies ranged from 2 to 15 years.

In total, the risk of 16 cancer types were evaluated at various anatomical locations.

A subgroup analysis was performed to investigate whether intake levels of cruciferous vegetables influenced the outcomes. The researchers categorized cruciferous vegetable intake based on servings per week into lower (less than 1 serving), moderate (3–5 servings), and higher levels (more than 4–7 servings) and compared cancer risks across these intake levels to assess dose-response relationships.

Overall, consuming cruciferous vegetables was associated with a reduced risk of developing cancer, with a 4% lower risk in the cohort studies, and a 23% lower odds in the case-control studies. However, these outcomes were highly heterogeneous.

The associations varied depending on the type of cancer. When looking specifically at cohort studies (the stronger study design), eating cruciferous vegetables was associated with a 5% lower risk of lung cancer, a 13% lower risk of bladder cancer, and a 15% lower risk of upper gastrointestinal cancer.

When looking at cancer types only evaluated in case-control studies (the weaker study design), eating cruciferous vegetables was associated with a 20% lower odds of gastric cancer and 18% lower odds of glioma (a type of brain cancer).

Notably, regional differences were observed in the associations. In Asian populations, eating cruciferous vegetables was associated with reduced risks of lung and esophageal cancers. In American populations, the strongest protective associations were seen for colorectal and renal cancers.

Cruciferous vegetables and cancer risk

Cancer remains one of the world’s leading causes of death and claims almost 10 million lives each year.^[1] As researchers continue to explore ways to prevent this devastating disease, diet has emerged as a significant area of study.^[2] Among the various foods examined, cruciferous vegetables like broccoli, kale, cauliflower, and cabbage have been noted for their rich content of bioactive compounds that could potentially help prevent cancer.^[3] However, their exact role in cancer prevention remains a subject of ongoing investigation.

The summarized meta-analysis builds on this biological rationale by providing large-scale evidence of an association between cruciferous vegetable intake and reduced cancer risk. With data from over 5.7 million participants across 229 observational studies, the study reported protective associations for several major cancers, including lung, renal, bladder, gastric, and prostate cancers. The associations were most pronounced for participants who consumes the most cruciferous vegetables, approximately 4 to 7 servings per week (approximately 1 serving or 100 grams daily).

Overall, the findings of the summarized study align closely with previous research that has investigated the association between fruit and vegetable intake and cancer risk reduction. A 2017 dose-response meta-analysis reported that every 200-gram increase in fruit and vegetable intake per day was associated with a 10% reduction in cancer risk.^[4] However, this previous study focused on both fruits and vegetables and also did not evaluate this association for different types of cancer. The current meta-analysis builds on this foundation by focusing specifically on cruciferous vegetables in the context of different cancer types. Although there are many meta-analyses on cruciferous vegetables (each examining a specific cancer type),^[5][6][7][8] the summarized study stands out by examining several cancer types within one major meta-analysis.

As such, the summarized study found that the degree of risk reduction varied widely across different types of cancer. For example, in cohort studies, bladder cancer had a 13% reduction in risk with higher intake levels, whereas lung cancer had a more modest reduction of 5%. This discrepancy may be explained by differences in tissue-specific biology. Bladder tissue, for example, is directly exposed to the bioactive metabolites that are excreted in urine, which potentially amplifies their protective effects. By contrast, lung tissue may benefit less due to differences in how these compounds are metabolized and distributed. Moreover, the underlying mechanisms that drive each cancer type are also distinct. Bladder cancer often involves carcinogens processed through the urinary system, whereas lung cancer pathways are more influenced by external toxins like smoking. Such variability underscores the need to consider both biological and environmental factors when interpreting these findings.

These complexities extend to regional differences in cancer risk reduction, which the study also highlighted. In Asian populations, cruciferous vegetables were associated with lower risks of lung and esophageal cancers. This may reflect traditional dietary patterns that emphasize raw or lightly cooked vegetables, which preserve bioactive compounds. In American populations, the most significant reductions were observed for colorectal and renal cancers, possibly due to differences in genetic predispositions, lifestyle habits, and cooking methods. These regional variations emphasize that the relationship between diet and cancer risk is shaped by a delicate interplay of culture, environment, and biology.

The reason why cruciferous vegetables are often associated with lower cancer risk could be attributed to their diverse array of bioactive compounds, including glucosinolates, flavonoids, carotenoids, and vitamins C and K.^[3] Glucosinolates are converted into isothiocyanates (e.g., sulforaphane) and indoles (e.g., indole-3-carbinol), which are thought to reduce oxidative stress, activate detoxification enzymes, and support DNA repair. Flavonoids and carotenoids contribute additional antioxidant and anti-inflammatory effects, and vitamin C enhances immune function and aids in neutralizing harmful free radicals. Among cruciferous vegetables, broccoli and Brussels sprouts stand out for their high glucosinolate content and ability to produce significant amounts of sulforaphane and indole-3-carbinol. Kale is another good choice, with a rich profile of glucosinolates and flavonoids. Cauliflower, though moderate in glucosinolate concentration, also remains an accessible and versatile option.

Applying these findings is relatively straightforward. People should aim for 4 to 7 servings of cruciferous vegetables per week, equivalent to approximately 400 to 700 grams. Although the study did not rank specific vegetables by effectiveness, varieties such as broccoli, kale, cauliflower, and Brussels sprouts are excellent choices. Additionally, preparation methods matter. For example, light steaming can enhance digestibility while preserving health-promoting compounds. Ultimately, choosing cruciferous vegetables that are affordable, accessible, and agreeable to individual preferences will ensure that these dietary habits are sustainable in the long term.

Taken together, this study’s findings underscore the potential role of cruciferous vegetables in reducing cancer risk, particularly for common cancers like lung, bladder, and colorectal cancer. Although further research is needed to refine scientific understanding of these associations, the current evidence supports incorporating these nutrient-rich vegetables into a balanced diet. By making small but consistent changes, individuals can take proactive steps toward better health and potentially lower their risk of cancer.

Although the findings are compelling, several methodological considerations temper confidence in the study results. While the large sample size of 5.7 million participants strengthens statistical power, the observational nature of the included studies limits causal inference. Furthermore, most studies relied on self-reported dietary data, which can introduce recall bias. In addition, the high degree of heterogeneity in terms of study populations, cancer types, and study designs complicates the interpretation of the results.