DEC 05, 2022 3:00 AM PST

Not All Plant-Based Diets are the Same, But Healthy Ones Could Reduce Risk of Colorectal Cancer

WRITTEN BY: Katie Kokolus

Recent research has linked the quality of a plant-based diet to different diseases, including cardiovascular disease, diabetes, and chronic kidney disease.  .  A new study published last week suggests that colorectal cancer (CRC) is joining this list.  

The quality, or “healthiness,” of an individual’s dietary patterns can contribute to the risk of health defects.  One method of assessing the quality of a plant-based diet involves a priori indices, an epidemiological approach to quantify specific characteristics of a dietary pattern, including how healthy the diet is.  A recent study published in BMC Medicine shows us that not all plant-based diets are created equal- at least not when protecting you from CRC.  

The study included almost 80,000 men (average age of 60) and over 93,000 women (average age of 59) participating in the Multiethnic Cohort Study.  The study explored the relationship between CRC risk and each of these three dietary patterns.  During a follow-up period of, on average, about 20 years, almost 5,000 cases of CRC developed in members of the cohort.  (For further reading, see our previous Labroots article discussed a study linking liver cancer to “forever chemicals,” which also analyzed data from patients enrolled in the Multiethnic Cohort Study.)

The researchers classified dietary patterns as follows: 1) an overall plant-based diet index (PDI), 2) a healthy plant-based diet index (hPDI), and 3) an unhealthful plant-based diet index (uPDI).  All three indices negatively weigh food derived from animals and differentially weigh plant-based food based on nutritional quality.  Assigning indices considered 16 food groups, a modification this research team made to previous studies, which included 18 food groups.  Healthy plant foods included whole grains, fruits, vegetables, vegetable oils, nuts, legumes, and tea/coffee.  Researchers considered refined grains, fruit juices, potatoes, and added sugars as less healthy plant-based foods.  Finally, animal foods included animal fat, dairy, eggs, fish/seafood, and meat. 

The researchers considered the data within each of the three indices by separating it into five portions known as quintiles.  The lowest quintile (Q1) indicated the lowest adherence to the dietary pattern, while the highest (Q5) indicated the greatest adherence to the dietary pattern. 

The analysis revealed that plant-based diet indices had a major impact, but only in men.  Among men with hPDI, those in Q5 had a 21% lower risk of developing CRC than those in Q1.  Similarly, among men with the greatest adherence to PDI exhibited a 24% less chance of developing CRC than those with the lowest adherence.  None of the three dietary patterns examined had a measurable impact on CRC development in women.

In addition, race may play a role in how plant-based diets impact CRC development as PDI conferred a stronger association in Japanese American, Native Hawaiian, and White men compared to African American or Latino men.

The authors conclude that plant-based diets rich in healthy plant foods with minimal amounts of less healthy plant foods conferred a lower risk of CRC in men.  Given these findings, public health programs aimed at improving the quality of plant-based foods and reducing animal-based food consumption could significantly impact CRC prevention. 


Sources: Eur J Nutr, PLOS Med, Clin J Am Soc Nephrol, BMC Med

About the Author
Doctorate (PhD)
I received a PhD in Tumor Immunology from SUNY Buffalo and BS and MS degrees from Duquesne University. I also completed a postdoc fellowship at the Penn State College of Medicine. I am interested in developing novel strategies to improve the efficacy of immunotherapies used to extend cancer survivorship.
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