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Plant-Based Diet Can Reduce Severity of Colorectal and Prostate Cancer

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Five fruit and veg a day may just keep prostate and colorectal cancer at bay, according to new research.

A review of dozens of separate studies, published in the International Journal of Cancer, found that healthy diets with a rich variety of plant-based foods were associated with a lower risk of mortality from colorectal cancer, while unhealthy diets and intake of sugary drinks were linked to a higher risk of mortality.

In another study of 2,062 men diagnosed with prostate cancer, those with the highest intake of plant foods had a lower risk of prostate cancer progression compared with those who ate fewer plant-based foods. These findings were published in JAMA Network Open.

You are what you eat

As part of their meta-analysis, the researchers from the International Agency for Research on Cancer and the World Health Organization analyzed 5 randomized controlled trials (RCTs) and 35 observational studies, which, in total, comprised of 30,242 individuals with colorectal cancer, 8,700 of whom died during the course of the study, 2,100 of which due to colorectal cancer.

Individuals living off Mediterranean and plant-based diets had lower risk of mortality than those eating unhealthy, “Western” diets. As for specific foods, whole grains and coffee (caffeinated or decaffeinated) were particularly noted for their link to lower risk of death. Sugary and artificially-sweetened drinks, on the other hand, were associated with worse cancer outcomes.

“This comprehensive and rigorous review of the current state of evidence offers useful guidance on some of the diet and lifestyle factors that could improve cancer survival, and potentially help people living with and beyond cancer enjoy longer, healthier lives,” said Dr. Helen Croker, assistant director of research and policy at World Cancer Research Fund International and co-author of the review.

“At the same time, it shows a clear need for more well-designed intervention and cohort studies to support the development of robust recommendations for colorectal cancer patients and health professionals. As we are seeing an increase of people diagnosed with colorectal cancer at younger ages, it is more important than ever that health advice is based on high-quality research.”

As part of the JAMA Network Open study, 2,062 men with biopsy-proven, nonmetastatic prostate cancer were enrolled across the US between 1999–2018 and asked to complete a diet and lifestyle questionnaire.

Between this first round of assessments and the follow-up appointments – which, on average, occurred 6.5 years later – 190 of the men’s cancers progressed and 61 died.

The researchers observed that the men who regularly ate more plant-based foods had a 47% lower risk of cancer progression.

Compared with men who ate fewer plants, men with high plant-intake scores typically ate 1.9 additional servings of vegetables, 1.6 additional servings of fruit, 0.9 more servings of whole grains, 1.0 less serving of dairy, 0.4 less servings of animal fat, slightly less egg and marginally less meat.

Although such high plant-based index scores weren’t associated with a reduced risk of progression overall, such an ultra-green diet was associated with a 55% lower risk of cancer progression among 680 individuals with more advanced cancers.

The researchers from the University of California, San Francisco, concluded that plant-based diets may help keep prostate cancer progress at bay, although they say future research and replication of their findings are needed.

Tsilidis K, Markozannes G, Becerra-Tomás N, et al. Post-diagnosis adiposity, physical activity, sedentary behaviour, dietary factors, supplement use and colorectal cancer prognosis: Global Cancer Update Programme (CUP Global) summary of evidence grading. Internat. Journ. of Canc. 2024. Doi: 10.1002/ijc.34904

Liu VN, Van Blarigan EL, Zhang L, et al. Plant-Based Diets and Disease Progression in Men With Prostate Cancer. JAMA Netw Open. 2024. doi:10.1001/jamanetworkopen.2024.9053