Recent Purdue Nutrition Science study provides gut check for bile acid derivatives that may reduce colorectal cancer risk

Written By: Rebecca Hoffa, rhoffa@purdue.edu

From coffee to protein bars to olive oil, people make many decisions every day about how they fuel their bodies. However, colorectal cancer risk typically is not front of mind when choosing what to eat.

Patricia Wolf, assistant professor in the Purdue University Department of Nutrition Science, recently published a study looking at secondary bile acid derivatives and their ability to reduce colorectal cancer risk. While a lot of work has been done looking at cancer-causing properties of secondary bile acids, a form of the chemical that helps absorb fat, little has been studied about their derivatives. These derivatives form when microbes in the gut adapt as a reaction to the harmful acids.

“The reason they’re interesting — and a lot of people are interested in them lately — is because secondary bile acids have antimicrobial effects, so they can create additional derivatives that are less toxic and have been of interest for the protection from colorectal cancer,” Wolf said.

Patricia Wolf

Wolf’s work, which was funded by grants from the American Cancer Society and National Institutes of Health, ultimately showed the nuances in diet and offered new areas of focus within a typical dietary pattern, including monounsaturated fatty acids (MUFAs).

“People have already shown that replacing 5% of saturated fatty acids with monounsaturated fatty acids is associated with decreased colorectal cancer mortality,” Wolf said. “We don’t know for sure that bile acids are the reason why, but it could potentially improve bile acid composition and reduce the inflammatory effect on the gut.”

However, while fiber and MUFAs were shown to support a protective bile acid profile, the team found conflicting results related to coffee and alcohol. Because other studies have pinpointed that consuming large amounts of alcohol or coffee may produce fewer protective measures within the gut, Wolf indicated that more work should be done in this area.

Wolf has also recently become interested in protein and its influence on the microbiome and colorectal cancer risk. With high-protein diets and protein-rich shakes, bars and powders trending across social media, Wolf noted she’s interested in diving deeper into protein sources and amounts to see what effect they’re having on microbial metabolism in the gut.

“I really think we need to be mindful about what that means in the context of a full dietary pattern,” Wolf said. “We’ve been seeing with some of our other studies we’re looking at with cysteine, a lot of the intake is from these protein powders. Maybe that’s great if it’s improving your overall dietary composition, but if you’re just consuming lots of protein and not having fiber or eating great otherwise, how is that impacting the microbiome and its metabolites? I don’t think we know for sure, so I think that is worth exploring more.”

Beyond her recent study, Wolf is also working with colleagues at the University of Illinois Chicago as well as College of Health and Human Sciences graduate student Pius Sarfo Buobu to study how environment, stress and dietary quality are impacting the gut microbiome and colorectal cancer risk.

“With this data set, we’re also looking at socioenvironmental barriers to dietary quality,” Wolf said. “We’ve observed that people with poor dietary quality are more likely to identify as Black and more likely to live in areas that have higher food insecurity.”

The research group has found those experiencing structural violence, or harm caused by social systems, were more likely to have higher levels of the stress hormone cortisol, which may make them more vulnerable to developing colorectal cancer.

“My colleague Lisa Tussing-Humphreys found that Black women have high hair cortisol levels, and that’s associated with reduced abundance of the more protective bile acid derivatives in their gut,” Wolf said.

Ultimately, through her work, Wolf hopes to uncover new opportunities to dive deeper into how both environments and nutrients are impacting colorectal cancer risk and translate these findings into healthier dietary patterns.

“We tend to focus on the same metabolites all the time, but we need to understand them in the context of the full dietary pattern and the functional redundancy of the microbiome,” Wolf said. “A lot of these microbes that make protective derivatives also make the bad ones, and so if we just rely on their looks, we don’t know for sure what they’re doing. Are they definitely doing something bad, or are they potentially doing something good?”