In the Health section of ABC News, I found an article—Could Cancer Prevention Be As Easy As Eating Strawberries?—claiming that consuming strawberries may help to prevent esophageal cancer because an experiment seemed to prove so. In the experiment, researchers administered 60 grams of freeze-dried strawberries daily for 6 months to 36 patients with precancerous lesions. Afterwards, it was observed that the “growth of lesions slowed significantly in 29 out of the 36 [patients].” Below is a video of ABC’s coverage on the experiment. While ABC, the researchers, as well as I, find the effects of eating strawberries very fascinating, further study is absolutely necessary to draw concrete conclusions [1].
ABC’s article led me to hypothesize—if strawberries really do prevent cancer, it must be a result of certain contents in these berries that have anti-tumor-activity abilities. To verify, I decided to research what compounds strawberries contain and what their roles are, if any, in interacting with cancer pathways. Consequently, I found that strawberries contain three major ingredients—ellegic acid; a flavanoid called quercitin, and ascorbic acid as known as vitamin C [2]; and in the following, I will discuss the functions of these compounds in light of the experiments performed with them.
Ellagic Acid
The research article Dietary Berries and Ellagic Acid Prevent Oxidative DNA Damage and Modulate Expression of DNA Repair Genes shows the role ellagic acid plays in preventing cancer and its growth. In the experiment, scientists induced oxidative DNA damage in female mice by injecting a carcinogenic estrogen metabolite and kept these mice on different diets for a total of 3 weeks. One group of mice was fed blueberries; another group strawberries; another group raspberries; and the last group pure ellagic acid. Results of this berry and ellagic acid diet are illustrated below.
The research article Dietary Berries and Ellagic Acid Prevent Oxidative DNA Damage and Modulate Expression of DNA Repair Genes shows the role ellagic acid plays in preventing cancer and its growth. In the experiment, scientists induced oxidative DNA damage in female mice by injecting a carcinogenic estrogen metabolite and kept these mice on different diets for a total of 3 weeks. One group of mice was fed blueberries; another group strawberries; another group raspberries; and the last group pure ellagic acid. Results of this berry and ellagic acid diet are illustrated below.
All mice groups showed a significant decrease in DNA damage—where raspberries led to the greatest decrease in DNA damage (59% decrease); pure ellagic acid led to 48% reduction;and blueberries and strawberries were equally effective (25% decrease). On top of decrease in DNA mutations, scientists also observed a “3 to 8 fold over-production of DNA repair genes” [3]. In my opinion, the results of this experiment are very sound. Observations of decrease in DNA adduct and of increase in DNA repair genes prove the positive effect of berries and ellagic acid because these two factors are correlated and chronological events that should both occur. In other words, in order for DNA repair to increase and thus DNA damage to decrease, DNA repair proteins would have to proliferate. This logical phenomenon was proven in the experiment.
Quercetin
Preclinical Colorectal Cancer Chemopreventive Efficacy and P53-Modulating Activity of 3’,4’,5’-Trimethoxyflavanol, a Quercetin Analogue tests for the role of quercitin in its interaction with tumor cells. In the experiment, scientists fed dietary 3’,4’,5’-Trimethoxyflavanol (TMFol), an analogue of quercetin, to two groups of mice—APCmin mice and HCT116 mice—in which both groups of mice experience colorectal tumor growth. For APCmin mice, TMFol was fed continuously up to 16 weeks; for HCT116 mice, TMFol was fed on day 7 prior to cancer injection or on day 7 after injection. Results showed decrease in tumor size and proliferation and increase in p53 production and apoptosis in all mice groups. The figure below illustrates p53 expression in APCmin mice (A) and HCT116 mice (C) [4].
Preclinical Colorectal Cancer Chemopreventive Efficacy and P53-Modulating Activity of 3’,4’,5’-Trimethoxyflavanol, a Quercetin Analogue tests for the role of quercitin in its interaction with tumor cells. In the experiment, scientists fed dietary 3’,4’,5’-Trimethoxyflavanol (TMFol), an analogue of quercetin, to two groups of mice—APCmin mice and HCT116 mice—in which both groups of mice experience colorectal tumor growth. For APCmin mice, TMFol was fed continuously up to 16 weeks; for HCT116 mice, TMFol was fed on day 7 prior to cancer injection or on day 7 after injection. Results showed decrease in tumor size and proliferation and increase in p53 production and apoptosis in all mice groups. The figure below illustrates p53 expression in APCmin mice (A) and HCT116 mice (C) [4].
Evidently, this experiment shows quercetin’s positive involvement in the tumor suppressive pathway. Quercetin leads to increase in p53 expression, which then leads to increase in cell death, and finally, tumor mass decrease. This logical pathway was found in the results of this experiment although the paper does not specifically talk about the mechanism of interaction with p53.
Ascorbic Acid
High Dose Concentration Administration of Ascorbic Acid Inhibits Tumor Growth in BALB/C Mice Implanted with Sarcoma 180 Cancer Cells via the Restriction of Angiogenesis shows the role ascorbic acid plays in suppression of angiogenesis (one of the hallmarks of cancer that involves blood vessel growth around tumors and supports tumor growth). In the experiment, mice were injected with Murine sarcoma S180 cells and then treated with high concentration dosages of ascorbic acid daily for about one month in different patterns. Results showed a 20% increase in survival and decrease in bFGF, VGF, and MMP2—all of which are angiogenesis-related proteins—in mice treated with ascorbic acid continuously before and after tumor injection. While this experiment did not provide quantitative results of tumor size, it did show that ascorbic acid displayed anti-cancer activity [5].
High Dose Concentration Administration of Ascorbic Acid Inhibits Tumor Growth in BALB/C Mice Implanted with Sarcoma 180 Cancer Cells via the Restriction of Angiogenesis shows the role ascorbic acid plays in suppression of angiogenesis (one of the hallmarks of cancer that involves blood vessel growth around tumors and supports tumor growth). In the experiment, mice were injected with Murine sarcoma S180 cells and then treated with high concentration dosages of ascorbic acid daily for about one month in different patterns. Results showed a 20% increase in survival and decrease in bFGF, VGF, and MMP2—all of which are angiogenesis-related proteins—in mice treated with ascorbic acid continuously before and after tumor injection. While this experiment did not provide quantitative results of tumor size, it did show that ascorbic acid displayed anti-cancer activity [5].
Through my mini-scale research, I am now convinced that strawberries do have cancer-prevention abilities. Because the individual ingredients found inside strawberries have been experimentally proven to have specific effects on tumor cells and their proliferative pathways, I believe their additive effect (found within a strawberry) can be even more impressive and effective. To put this theory into practice, doctors could try prescribing strawberries to their cancer patients for consumption on a daily basis. Perhaps strawberries can not only suppress tumor growth, but can also fix the potential damages caused by radiation therapy and chemotherapy.
[1] Carollo, K. (2011 April 6). Could Cancer Prevention Someday Be As Easy As Eating Strawberries? ABC News.
[2] Avarus Z1M (2010). Strawberries Anti-Cancer. WordPress.
[3] Aiyer, Harini S. et al. (2008 March 12). Dietary Berries and Ellagic Acid Prevent Oxidative DNA Damage and Modulate Expression of DNA Repair Genes. International Journal of Molecular Sciences, 9(3): 327–341.
[4] LM, Howells et al. (2010 July 13). Preclinical Colorectal Cancer Chemopreventive Efficacy and P53-Modulating Activity of 3’,4’,5’-Trimethoxyflavanol, a Quercetin Analogue. Cancer Prevention Res., 3(8):929-39.
[5] CH, Yeom et al. (2009 August 11). High Dose Concentration Administration of Ascorbic Acid Inhibits Tumor Growth in BALB/C Mice Implanted with Sarcoma 180 Cancer Cells via the Restriction of Angiogenesis. Journal of Translational Medicine, 7:70.
[2] Avarus Z1M (2010). Strawberries Anti-Cancer. WordPress.
[3] Aiyer, Harini S. et al. (2008 March 12). Dietary Berries and Ellagic Acid Prevent Oxidative DNA Damage and Modulate Expression of DNA Repair Genes. International Journal of Molecular Sciences, 9(3): 327–341.
[4] LM, Howells et al. (2010 July 13). Preclinical Colorectal Cancer Chemopreventive Efficacy and P53-Modulating Activity of 3’,4’,5’-Trimethoxyflavanol, a Quercetin Analogue. Cancer Prevention Res., 3(8):929-39.
[5] CH, Yeom et al. (2009 August 11). High Dose Concentration Administration of Ascorbic Acid Inhibits Tumor Growth in BALB/C Mice Implanted with Sarcoma 180 Cancer Cells via the Restriction of Angiogenesis. Journal of Translational Medicine, 7:70.
