Q&A: The microbiome and cancer

A well-balanced diet that’s rich in plant foods, including legumes
and whole grains is important for everyone, including cancer
survivors. Consistent healthy choices can help prevent weight gain and
decrease body fat, which are linked to better quality of life and a
lower risk of cancer and cancer recurrence. In healthy individuals,
eating well, exercising and maintaining a healthy weight have been
shown to decrease cancer risk.

Another important and perhaps overlooked reason for maintaining a
balanced diet is to promote a healthy microbiome, which can have a
number of important health benefits. Below, Carrie Daniel-MacDougall, Ph.D., assistant
professor of Epidemiology, answers questions about the role the
microbiome plays in several health conditions, including cancer.

What is the microbiome?

The microbiome is composed of bacteria — both good and bad — that
live and coexist inside of and around you: on your skin and eyes, in
your mouth and throughout your GI tract. Your microbiome is a big part
of who you are and what makes you different from everyone else. In
fact, it’s bigger than all of us.   

The microbiome holds clues about what you’ve been exposed to, what
illnesses you may be prone to and what treatments may be most
effective. It can even tell us about your favorite foods! We are now
learning how to decipher these many signals.

How does the microbiome impact your health overall?

The microbiome has been linked to obesity, inflammatory bowel
disease, diabetes, heart disease and a number of cancers, such as
colorectal cancer, pancreatic cancer and breast cancer. I imagine that
this list will grow as we learn more about the role the microbiome
plays in diet and obesity, which is linked to many diseases.

Eventually, we may be able to understand how your microbiome affects
your personal health by reading your microbiome profile along with
blood sugar and cholesterol levels. But for now the best answer is
that balance in the microbiome promotes good health.

Can we influence the microbiome to lower cancer risk?

I think an individual’s diet is the safest place to start harnessing
the microbiome for cancer prevention. Short-term studies have shown
that improvements in overall dietary habits positively impact the
microbiome and other markers of cancer risk. However, because these
results are seen in such a short time, they are just as easily
reversible. Therefore, if you’re trying to prevent cancer, the dietary
changes have to be sustained long-term. 

Why is the microbiome important for cancer patients and/or survivors?

Given that the microbiome and the immune system are intrinsically
linked, harnessing the microbiome could be important for everything
from side effects to treatment response to long-term survival. This is
an area of active research, but there aren’t any safe and proven
answers yet. Based on a lack of evidence, I would not suggest that a
patient in active treatment try to independently manipulate his or her
microbiome as that may easily do more harm than good.

What can people do personally to affect their microbiomes?

In healthy people, it’s primarily diet and medication use that
impact the microbiome. Your microbiome depends on you for food, so you
decide what it’s eating today and every day. Tweaking your diet
therefore is a natural way to influence the bugs you have, fostering
the good and crowding out the bad.

Fiber-rich vegetables, fruits and whole grains, which have long been
recommended for cancer prevention, are also good “pre-biotic foods”
that can help feed the good bacteria you already have.

Probiotics may sometimes be recommended by your doctor after taking
antibiotics or other situations that can wipe out your microbiome. You
can also get probiotics through food sources, such as yogurt and other
fermented dairy products.

What current research are you working on in this area?

I am currently interested in how prebiotic foods and overall dietary
patterns impact the microbiome and colorectal cancer risk. After we
observed the diets and microbiomes in both healthy people and those
with precancerous colorectal polyps, we were excited by the results.
However, we have more to learn.

So, we’ve initiated our first trial on the diet and microbiome here at MD Anderson. Beans have long been linked to
cancer and heart disease prevention. Our goal is to find out if beans
can improve the healthy bacteria in the digestive system and reduce
the effects of obesity on cancer risk.

For more information about participating in the trial, call
713-792-2062 or email begone@mdanderson.org.