by Karen Collins, R.D., American Institute
for Cancer Research
Probiotics may offer other health benefits,
but one receiving more support recently is the possibility
of helping to prevent colon cancer. If results of a small
but well-controlled study in Ireland are repeated, probiotics
– live bacteria that can benefit health – might
have a place alongside vegetables, legumes, whole grains
and regular exercise in our strategies to lower risk of
cancer.
Your digestive tract is home to hundreds
of different types of bacteria. Most of them are considered
beneficial, crowding out harmful bacteria, speeding digestion
and perhaps even enhancing immune function. One of the most
accepted health benefits of probiotics comes from taking
the probiotics along with or following antibiotic treatment.
Antibiotic medicines can sometimes kill the gut’s beneficial
bacteria along with the illness-causing bacteria. Without
the “good” bacteria in control, sometimes harmful
bacteria can multiply, leading to diarrhea. Studies suggest
that probiotics restore a healthy bacteria population in
the gut and prevent diarrhea.
The recent study focusing on probiotics
and colon cancer was published in February. Because colon
cancer takes years to develop, the scientists looked at
various signs of its early development. This study included
80 people who either had colon cancer tumors or non-cancerous
colon polyps (precursors to cancerous tumors) recently removed.
Participants were randomly assigned to receive either a
probiotic or placebo (an inactive substance). The probiotic
contained two types of bacteria often seen as protective
of colon health (Lactobacillus rhamnosus and Bifidobacterium)
combined with a prebiotic. Prebiotics are nondigestible
food ingredients that feed the growth of healthful bacteria
in the colon. The combination of probiotics and prebiotics
is called synbiotics.
After 12 weeks, researchers found that
the balance of colon bacteria had changed in those receiving
the synbiotic, with more Lactobacillus and Bifidobacterium
and less of the bacteria (Clostridium) that is linked with
increasing cancer risk. Compared to patients who received
placebos after polyp removal, those who received synbiotics
showed decreased DNA damage in the lining of the colon and
decreased growth and reproduction of colon cells (which
increase in colon cancer). Neither of the groups reported
adverse effects of synbiotics. These findings are consistent
with earlier studies showing that “bad” bacteria
can produce substances that initiate or promote development
of colon cancer. Probiotics have been shown to decrease
abnormal colon cell development and DNA damage in animals.
Research studies often investigate probiotics
using controlled doses of supplements, but you can also
get probiotics from foods. Most fresh yogurts contain live,
active cultures; check labels to be sure. Drinks that provide
probiotics include dairy and soy versions of kefir and acidophilus
milk. Fermented soy products (including miso and tempeh)
and sauerkraut may also supply probiotics, but little data
is available to confirm the amounts or types of bacteria.
What about prebiotics to support growth
of healthful bacteria? Inulin (which is extracted from chicory
root) and oligofructose are found in prebiotic and synbiotic
supplements. But so far research does not show that these
prebiotics offer any advantage over the dietary fiber found
in vegetables, fruits, whole grains and dried beans.
Probiotic and synbiotic supplements
come in capsules, powders and liquids. If you’re going
to use one of these products, check the label to be sure
you will get at least one billion live bacterium per day.
Because supplements are not regulated by the government,
look for products with USP-Verified or CL-approved on the
label, which means they have undergone testing by the U.S.
Pharmocopeia or Consumer Lab, respectively. Probiotic and
synbiotic supplements are considered safe, and no health
risks have been reported related to their use. Yet benefits
are far from certain, especially since results may differ
with different types of bacteria. While we wait for more
research, use probiotics and/or synbiotics if you wish but
make sure to focus on other, more proven cancer prevention
strategies, such as exercise, weight control and eating
a wide variety of fruits and vegetables.
