Resistant Starch and Cancer Risk: What You Need to Know

Understanding Resistant Starch: Its Impact on Cancer Risk and Dietary Sources

While no single food can cure or prevent GI cancer, I’m always looking at the research regarding what components of foods are associated with a reduced risk of cancer. Lately, I’ve been curious about resistant starch. 

What is resistant starch? Resistant starch is one type of dietary starch. Most starches are digested by enzymes located in the small intestine called amylases. However, resistant starch is “resistant” to these enzymes, hence the name. Instead, it passes to the colon, where it is fermented by microbiota. 

During this fermentation process, important metabolites are created as a byproduct. These metabolites have many different uses by the body, including affecting cancer and chronic disease processes and risk. Because this process occurs in the colon, it is natural to wonder what its impact on colon cancer could be.

Now, when colon cancer is being studied, researchers often look at individuals with Lynch syndrome. Lynch syndrome is a hereditary disorder that increases the risk of several types of cancer, especially colorectal cancer. It is also known as hereditary nonpolyposis colorectal cancer (HNPCC). The other cancers it increases risk for include uterine, stomach, liver, kidney, brain, and certain skin cancers. While individuals with Lynch syndrome are at increased risk of these cancers, it is not a guarantee that they will get cancer. 

The CAPP2 trial (Colorectal Adenoma/Carcinoma Prevention Programme) was a trial that looked at the impact of supplementation with resistant starch on cancer incidence in people with Lynch Syndrome. Over 400 participants received 30g of resistant starch daily for four years, whereas the control group took a placebo. Ten years later, they followed up on the participants to see how many developed cancer. Here’s where the findings get interesting. 

The results analysis showed no significant impact of resistant starch on colon cancer in the first ten years following the supplementation. However, they found a 46% relative risk reduction in non-colorectal cancer cases in the group that took the resistant starch. This risk reduction was especially seen in cancers of the upper GI tract. 

I am interested in seeing if continued follow-up on these participants in the long term yields different results. But in the meantime, what do these results mean for us? Should we start supplementing with resistant starch out of an abundance of caution? These results alone are not enough to definitively confirm that resistant starch reduces cancer risk and certainly not sufficient to warrant starting supplementation. Yet there is no doubt that the results are promising! 

Instead of going overboard with supplements (which, reminder, the FDA does not regulate), it probably couldn’t hurt to see if you’re already getting resistant starch in the diet and then go from there. 

Examples of foods containing resistant starch include: 

• Bananas (especially unripened)
• Potatoes
• Cooked and then cooled rice
• Whole grains
• Beans
• Peas 
• Lentils

If you are already aiming to get a variety of plant-based foods in your diet, you are likely well on your way to consuming many cancer-fighting nutrients, phytonutrients, and fiber. Including resistant starch!

1. _{Birt, D.DF., Bolylston, T., Hendrich, S., Jay-Lin, J., Hollis, J., et al. (2013). Resistant starch: promise for improving human health. Journal of Advanced Nutrition, 4(6): 587-601.}
2. _{Centers for Disease Control and Prevention (2023). Lynch Syndrome. Retrieved August 22, 2023.}
3. _{Mathers, J.C., Elliot, F., Macrae, F., Mecklin, J.P., Moslein, G., et al. Cancer prevention with resistant starch in lynch syndrome patients in the CAPP2- randomized placebo controlled trial: planned 10-year follow-up. (2022). Cancer Prevention Research, 15(9): 623-634.}