Using Resistant Starches to Inhibit Colon Cancer

1. Using Resistant
Starches to Inhibit
Colon Cancer
Marissa N. Jackson

2. Abstract
Scientists have discovered that many cases of colon cancer are greatly influenced by a
person’s diet, and less impacted by genetic background. Eating plenty of resistant starches
(starches that are able to be fermented in the large intestine as they escape digestion in the small
intestine) could to inhibit colon cancer through preventing the formation of preneoplastic lesions,
such as aberrant crypt foci (ACF) in our bodies. Studies have shown that those mice injected
with cancer inducers, such as azoxymethane (AOM) contain higher amounts of ACF than those
mice that are not injected with cancer inducers and are instead injected with a saline control. 60
male A/J mice were divided into 4 equal groups and placed on one of 4 diets (Control Starch,
OSA, HA7, and RS5) each with a varying resistant content. There were 10 AOM injected mice
and 5 saline injected mice per group. After euthanization of the mice by carbon dioxide (CO2),
the colons were extracted and stained to determine the amount of ACF in the colons. The HA7
diet was the most protective against colon cancer because the mice that consumed this diet
possessed the smallest number of ACF lesions in their colons (the average was 0.6). On the other
hand, the control diet was the least protective against colon cancer because the diet contained no
resistant content. Thus, I hypothesized that resistant starch fed in a diet would be able to inhibit
the initiation and progression of colorectal cancer and thus, inhibit the formation of ACF.
Introduction
Preneoplastic lesions, such as Aberrant Crypt Foci (ACF), are present in high amounts in
the colon in a cancer patient. Resistant starches are thought to inhibit colon cancer through

3. preventing the formation of ACF in our bodies. Resistant starches are able to be fermented in the
large intestine and the colon as they escape digestion in the small intestine, which helps maintain
normal healthy colonic tissue and decreases the amount of precancerous lesions. (Live Science).
According to the American Cancer Society, 50,830 people die from colon cancer every
year. More African Americans than any other race are diagnosed with colon cancer. Also, more
men than women are diagnosed with colon cancer (American Cancer Society). The various
symptoms of colon cancer include diarrhea or constipation, the feeling that the bowel has not
completely emptied after the bowel movement, abdominal discomfort, such as gas, bloating, and
cramps, rectal bleeding, unexplained weight loss, unexplained iron-deficiency anemia (low red
blood cell count), and weakness and fatigue (Mayo Clinic).
There are four methods of colon cancer screening. The first method is the Fecal Occult
Blood Testing method where the physician looks for blood in the stool from the bleeding of
polyps and cancer cells. This test is taken at home and given to a physician and can reduce colon
cancer deaths by 30%. The second method is a Sigmoidoscopy, where the doctor examines the
rectum, polyps, cancer cells, and the lining of the lower colon using a lighted tool. This test is
taken in the doctor’s office without anesthesia. The next method is called the Barium Enema,
which is an x-ray of the colon. The enema clears out the colon and the radiologist puts a dye in
the colon and takes x-ray pictures of it. However, this method is flawed because the radiologists
are unable to accurately find polyps. The final method is a colonoscopy. This is when a physician
takes a lighted tube and looks at the entire lining of the colon. Some anesthesia is given in this
method and this method is commonly used to identify cancer cells and polyps as well (Ernest T.
Hawk et al, 2009).

4. The various treatments for colon cancer include surgery, chemotherapy, and radiation
therapy. Surgery is used for the early stages of colon cancer and completely removes the cancer
tumors. Chemotherapy kills the remaining cancer cells and radiation therapy is typically
combined with the treatment of chemotherapy (National Cancer Institute).
In order to test the inhibition of colon cancer, our lab used 5 week old male A/J mice.
There was a control diet and a control injection (saline) used so that we are able to determine the
number of preneoplastic lesions in a control mouse in comparison to the number of lesions found
in the mice being fed one of three other diets (HA7, OSA, and RS5) as well as the number of
lesions found in the mice who were injected with saline compared with those who were injected
with the carcinogen, Azoxymethane (AOM). In order to prevent colon cancer, resistant starches
must be consumed. Thus, I hypothesized that resistant starch fed in a diet would be able to
inhibit the initiation and progression of colorectal cancer and thus, inhibit the formation of ACF.
Materials and Methods
Our lab received 60 male A/J mice at 5 weeks old. We acclimated them on the control
diet for 2 weeks, then gave them intraperitoneal injections for 4 weeks while they remained on
the control diet. 40 of the 60 mice were injected with AOM at a dose of 7.5 mg/kg of bodyweight
and the saline was injected as a control into the remaining 20 mice using the same dose as was
used for the AOM.

5. After the injections, the mice were divided into 4 equal groups with 10 AOM injected
mice and 5 saline injected mice per group. Then, they were fed one of four different diets
(Control Starch, HA7, OSA, and RS5) for 10 weeks. There were 15 mice per diet.
While the mice were on their diets, it was my responsibility to prepare the diets on
Wednesdays and Fridays and feed them on Tuesdays and Thursdays. Then, on Wednesdays I
was also required to observe and record the changes in the mice, such as weight loss or gain, loss
of fur, and their movements. We also had to keep track of food disappearance to properly assess
how much food that we should provide each mouse.
After the 10 week diet, the mice were euthanized with carbon dioxide (CO2) and their
colons were extracted for analyses. Then, the colons were first stained with alcian blue, followed
by a short counterstain to observe and record the number of ACF lesions that were present.
Results
As shown in Figure 1, the mice in the saline groups contained almost no ACF lesions on
average, as expected. On average, the mice on the HA7 diet only contained 0.6 ACF lesions in
their colons. The mice on the RS5 diet, contained on average 1.7 ACF lesions in their colons.
The average number of ACF lesions present in the colons of the mice fed the control diet was 1.2
and the average number of ACF lesions present in the colons of the mice that were fed the OSA
diet was 1.3.

6. The mice that were fed the RS5 or OSA diet had a few more ACF lesions present than the
mice that were on the control diet. The average number of ACF lesions present in the mice fed
the HA7 diet is significantly lower than the number of ACF lesions present in the mice fed the
control diet, and has shown to be able to effectively combat the effects of the AOM and inhibit
progression of this preneoplastic lesion and thus colorectal cancer.
As shown in figure 2, the bodyweights of the mice on each diet varied. From week 0 to
week 1, the bodyweights of the mice increased immensely in each diet. The same increase
occurred from week 1 to week 2. Then, there were small variations in weight following week 2.
On the day of the euthanization, the average weight of the CS/saline mice was 26.2 grams, 26.1
grams for the CS/AOM mice, 25.7 grams for the HA7/saline mice, 25.2 grams for the
HA7/AOM mice, 22.5 grams for the OSA/saline mice, 21.3 grams for the OSA/AOM mice, 24.7
grams for the RS5/saline mice, and 24.5 grams for the RS5/AOM mice. However, there were no
significant differences observed in bodyweights between the mice in any treatment group.

7. Figure 1

8. Figure 2

9. Figure 3
Discussion

10. Figure 1 shows the average number of ACF lesions found in the mice that were
on each diet. Thus, my data shows that consuming the HA7 diet would prevent colon cancer
better than consuming any of the other diets and the HA7 diet would be the diet of choice in
inhibiting colon cancer. Also, my results show that the RS5 and OSA diets’ resistant components
were so high that they actually made the effects of the AOM worse, which caused more ACF
lesions to form.
Figure 2 shows the average bodyweights of the mice in each group weekly. Our results
show that the treatments did not significantly affect the bodyweights.
The mice that were being fed the diet containing the least resistant content (control
starch) had the highest bodyweight, then the mice that were being fed the diet with the next
lowest resistant content (HA7) weighed the next highest, the mice that were being fed the diet
with the second highest resistant content (OSA) weighed the least, and finally the mice that were
being fed the diet with the highest resistant content (RS5) weighed the second lowest. Thus, I can
conclude that the more resistant a diet is, the lower one will weigh. Therefore, I do not believe
that there is any correlation between resistant content and bodyweight.
Based on the results, the HA7 diet is the diet of choice in inhibiting colon cancer.
References
1. Angelle, Amber. "Colon Cancer: Causes, Symptoms and Treatments." LiveScience.com.

11. TechMedia Network, 2013. Web. 16 July 2013.
2. "What Are the Key Statistics about Colorectal Cancer?" What Are the Key Statistics
about Colorectal Cancer? American Cancer Society, 17 Jan. 2013. Web. 16 July 2013.
3. Staff, Mayo Clinic. "Definition." Mayo Clinic. Mayo Foundation for Medical Education
and Research, 13 Aug. 2011. Web. 16 July 2013.
4. Hawk, Ernest T. "Colon Cancer Screening Methods." Iowa State University E-Library.
NIH Senior Health, 2009. Web. 16 July 2013.
5. "Colon Cancer Treatment." National Cancer Institute. National Institutes of Health, 16
May 2013. Web. 16 July 2013.