In a study of pigs, researchers found that supplementing a high-calorie diet (HCD) with purple potatoes led to a reduction in levels of interleukin-6 (IL-6) - a pro-inflammatory protein that studies have shown can promote colon cancer - in the colon.
Study co-author Jairam K.P. Vanamala, a professor of food sciences at Pennsylvania State University in State College, and colleagues say that their results support previous research that claims that plant-based diets are linked to lower colon cancer risk.
The researchers recently reported their findings in The Journal of Nutritional Biochemistry.
According to the American Cancer Society, there will be 95,520 new cases of colon cancer diagnosed in the United States this year.
If caught early, the 5-year survival rate for colon cancer is around 92 percent. For patients whose colon cancer has metastasized, or spread to other parts of the body, 5-year survival stands at around 11 percent.
Studies have suggested that dietary changes - such as reducing meat intake and increasing the consumption of whole grains, fruits, and vegetables - can help to lower the risk of colon cancer.
Prof. Vanamala and team expand on these findings by shedding light on how brightly colored fruits and vegetables might contribute to better colonic health.
"What we are learning is that food is a double-edge sword - it may promote disease, but it may also help prevent chronic diseases, like colon cancer," says Prof. Vanamala. "What we don't know is, 'how does this food work on the molecular level?' This study is a step in that direction."
Purple potatoes and pigs
The researchers came to their findings by feeding pigs one of three diets for 13 weeks: an HCD, an HCD supplemented with purple potatoes (raw or baked), and a standard diet (the control diet).
As with many colorful fruits and vegetables, purple potatoes contain beneficial nutrients at significantly higher levels than their white-fleshed counterparts.
"Specifically, purple-fleshed potatoes are rich in phenolic acids and anthocyanins," the researchers note. "[...] white potatoes may have helpful compounds, but the purple potatoes have much greater concentrations of these anti-inflammatory, antioxidant compounds." Previous studies have shown that these compounds have anti-cancer properties.
After the 13-week diet interventions, the team screened the colonic tissue of the animals in order to determine how each diet had affected gene expression and levels of pro-inflammatory markers.
Purple potatoes prevented inflammation
The analysis revealed that compared with pigs fed the control diet, pigs fed only the HCD showed an increase in levels of IL-6, which could increase the risk of colon cancer and other diseases.
However, the pigs fed the HCD supplemented with purple potatoes had IL-6 levels that were six times lower than that of the control group.
Based on these results, Prof. Vanamala and team suggest that targeting IL-6 with purple potatoes and other colorful fruits and vegetables high in anti-inflammatory compounds could be a feasible way to prevent colon cancer and other diseases.
"We observed that dietary supplementation of purple-fleshed potatoes, even after processing, prevented HCD-induced inflammation. Ultimately, this work is important as [a] chronic inflammatory environment can lead to a multitude of diseases, including type 2 diabetes and colon cancer."
"The prevalence of chronic inflammation-promoted diseases are on the rise around the globe," the team adds, "thus, it is critical to develop safe, effective, and affordable dietary interventions or strategies to help prevent the onset of diseases."