The following is an in-depth analysis of the research into food (particularly fruits and vegetables) and how they may prevent, protect against, or possibly provide complementary, therapeutic effects for human cancers.
This information originally appeared in my e-book, Green Smoothie Remedies & Prevention (2011).
Cancer Protection & Antioxidants
I am not suggesting that green smoothies are a cure for cancer or an alternative to cancer treatment, but their super high antioxidant levels and other nutrients help reduce oxidative stress, neutralize free radicals and just might give you an edge on keeping cancer out of your life along with a healthy diet and lifestyle.
An overwhelming body of evidence points to a reduced risk of various types of cancer with an increased intake of fruits and vegetables. Some researchers estimate that 1/3 of cancer deaths might be prevented with a higher intake of fruits and vegetables.
Others estimate that cancer rates would decrease by 20% in populations with a diet higher in fruits and veggies.
A growing body of research indicates that an increased intake of fruits and vegetables in the diet may reduce the risk of developing cancer of the mouth, larynx, esophagus, stomach, colon, lung, kidney, prostate, breast and rectum.1
Colorectal (Colon) Cancer Risk Reduced With Dietary Fiber
Numerous studies have shown that an increase of dietary fiber is associated with a decreased risk of colorectal cancer.
A massive study of 519,978 people ages 25-70 from ten European countries analyzed dietary intake, specifically fiber intake, and incidence of colon cancer. The interpretation of the results of the study was that “[in] populations with low average intake of dietary fibre, an approximate doubling of total fibre intake from foods could reduce the risk of colorectal cancer by 40%”. 2
There was not a particular source of dietary fiber that was identified to be more effective than another. Green smoothies are an excellent source of fiber in the diet. The average 20-ounce green smoothie has about 15 grams of fiber, depending on which fruits and greens you use in the recipe.
Apple Pectin As A Possible Chemoprotective Substance Against Colon Cancer
Apples are rich in a digestion-resistant fiber called pectin that is then fermented in the large intestine (colon). The microflora in the colon ferments pectin (and other dietary fiber) to produce a substance called butyrate. Butyrate is thought to be a “chemopreventive metabolite that can prevent the occurrence of colorectal cancer, one of the most abundant types of cancer in Western industrialized countries.” 3 Histone deacetylase inhibitors, such as butyrate, have been studied for their potential for use in cancer therapy. 4
While butyrate has been shown to inhibit colon tumor cells 5, the signaling factors are not well understood. 6
Bananas, Lettuce & Apple Associated With a Lower Risk of Colon Cancer
A study in Uruguay assessed dietary patters and colorectal cancer risk using a food frequency questionnaire on 61 food items. The researchers discovered that a reduction of risk was associated with an increased intake of fruits and vegetables, particularly lettuce, apple and banana, with banana intake providing the strongest protection. 7
Breast Cancer Risk Reduced With Increased Fruit & Vegetable Intake – Especially Dark Leafy Greens, Cruciferous Vegetables, Carrots, Tomatoes, Banana, Watermelon, Papaya and Cantaloupe
A health study in Guangdong, China, matched 438 breast cancer patients with 438 controls (cancer-free) within a similar age range and analyzed dietary intake of fruits and vegetables using a food frequency questionnaire and faceto-face interviews.
The results indicated that those who ate more fruits and vegetables had a lower risk of developing breast cancer than those who did not. Those who ate more dark leafy greens, cruciferous vegetables (kale, bok choy, broccoli), carrots, tomatoes, bananas, watermelons, papayas and cantaloupes appeared to have a lower risk of developing breast cancer. 8
Concord grape juice has been shown to have a protective effect in decreasing the susceptibility of rat mammary glands to tumors induced from 7,12dimethylbenz[a]anthracene (DMBA), a chemical carcinogen used in animal cancer studies. 9
A May 2005 report in the journal Clinical Cancer Research suggested that dietary flaxseed has the potential to reduce tumor growth in patients with breast cancer.
The studies aim was to determine the “effects of dietary flaxseed on tumor biological markers and urinary lignan excretion in postmenopausal patients with newly diagnosed breast cancer”. Women who ate a flaxseed-containing muffin each day over a 32-day period had a higher level of lignans from consuming flaxseeds. Lignans have been shown to reduce tumor growth in rats. 10
Kidney Cancer (Renal Cell Carcinoma)
A study that analyzed the dietary intake of fruits and vegetables among 61,000 Swedish women aged between 40 to 76 years over a 13.4-year period found that a diet rich in fruits and vegetables was associated with a reduced risk of renal cell carcinoma. During the study, 122 women developed this cancer.
Among the fruits and vegetables that showed the greatest potentially protective benefit were bananas, root vegetables and white cabbage. “Frequent consumption of salad vegetables (once or more per day) decreased the risk [of renal cell carcinoma] by 40%, in comparison to no consumption.” 11
Resveratrol May Protect Against A Variety Of Cancers And Provide Therapeutic Benefits
Resveratrol, a potent antioxidant found in red grapes, has been associated with chemopreventive benefits and shows some potential for therapeutic benefits for “cancers of the breast, prostate, stomach, colon, pancreas, and thyroid; melanoma; head and neck squamous cell carcinoma; ovarian carcinoma; and cervical carcinoma”. 12, 13
Apples and Apple Products May Reduce the Risk Of Lung and Colon Cancer
A 2008 review in the journal Planta Medica that investigated the evidence linking apple consumption and the use of apple products to prevent certain cancers yielded the following conclusions:
“Apple products have been shown to prevent skin, mammary and colon carcinogenesis in animal models. Epidemiological observations indicate that regular consumption of one or more apples a day may reduce the risk for lung and colon cancer.” 14
Cruciferous Vegetables May Reduce Cancer Risk
A March 2004 review in the journal Integrative Cancer Therapies examined the link between the consumption of cruciferous vegetables and cancer risk. Specifically, it looked at a compound found in crucifers called glucosinolates.
The American Institute of Cancer Research estimates that cancer rates would reduce by up to 20% in the general population if the only change in diet were an increase to five servings of fruits and vegetables per day. However, the review states, “epidemiological studies provide evidence that the consumption of cruciferous vegetables protects against cancer more effectively than the total intake of fruits and vegetables”.15
Antioxidants And Anti-Cancer Benefits
Dietary antioxidants that are plentiful in fruits and vegetables, and especially berries, have been extensively studied for their potential to protect against a variety of diseases including cancer.
There is a body of evidence that suggests that an increased intake of fruits and vegetables (which contain high amounts of antioxidants) may provide a cancer chemopreventive effect.
A variety of studies have looked into certain dietary antioxidants such as polyphenols, curcumin, genistein, resveratrol, lycopene, and lupeol from foods like berries, red/purple grapes, pomegranates, tomatoes and a variety of fruits and vegetables and their link to cancers of the skin, prostate, breast, lung and liver. 16
Berries, in particular, have been shown to contain high antioxidant potential due to their high levels of phenolic and flavonoid compounds. Berries are at the top of the list of antioxidant-rich foods that “reduce oxidative DNA damage, stimulate antioxidant enzymes, inhibit carcinogen-induced DNA adduct formation and enhance DNA repair”. 17
Antioxidant-rich berries that show promise for further clinical research (based on promising in vitro – cell culture – studies) include black raspberry 18, blackberry, blueberry, cranberry, red raspberry and strawberry. 19
Pomegranate is another fruit that has been studied extensively for its potential anticancer benefits due to its high antioxidant load.
Research has shown that pomegranate extracts selectively inhibit the growth of breast, prostate, colon and lung cancer cells in vitro (cell cultures). Pomegranate juice has also been shown to inhibit growth of lung, skin, colon and prostate tumors in animal studies. 20
According to a January 2007 review in the Journal of Ethnopharmacology, components in pomegranate “juice, peel and oil have also been shown to possess anticancer activities, including interference with tumor cell proliferation, cell cycle, invasion and angiogenesis”. 21
Pomegranate Juice and Prostate Cancer
Various animal studies have shown a possible benefit in pomegranate juice for prostate cancer. Once such study published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) showed a significant inhibition of tumor growth in mice implanted with prostate cancer cells. It was suggested “pomegranate juice may have cancer-chemopreventive as well as cancerchemotherapeutic effects against prostate cancer in humans”. 22
A recently concluded clinical trial is currently analyzing the potential effects of pomegranate juice on prostate cancer in humans. 23
Flaxseeds have been shown to stunt the growth of prostate tumors in men. A 2007 study led by Duke University Medical Center researchers showed that men who supplemented their diet with ground flaxseed (30 grams per day for an average of 30 days) slowed tumor growth compared to men who did not supplement with flaxseeds in the diet. 24
Flaxseed can be ground up in a coffee grinder (or high speed blender) and added to green smoothies for a dose of omega-3 essential fatty acids.
Carotenoids May Protect Against Carcinogenic Skin Damage From UV Light
Emerging research is beginning to study the link between dietary carotenoids, especially lutein and zeaxanthin, and their role in promoting both eye and skin health. There is some evidence to suggest that both lutein and zeaxanthin may play a role in protecting the skin from UV-induced DNA damage that results from sun exposure – a risk factor for developing certain types of skin cancers. 25,26
Green Smoothie Foods To Fright & Prevent Cancer
The general consensus is that an overall increase of fruits and vegetables in the diet may reduce the risk of developing certain cancers.
The foods that have been studies most extensively include apples, bananas, lettuce, cruciferous vegetables (kale, bok choy, broccoli, cabbage), tomatoes, watermelon, papayas, cantaloupe, concord grapes, flaxseed, root vegetables (carrots, parsnips, beets), red grapes, pomegranates, black raspberries, raspberries, blueberries, blackberries, cranberries and strawberries.
5 Green Smoothie Recipes To Help Prevent Cancer
To make these green smoothies, simply add the liquid to your blender first, followed by the soft fruit. Then add frozen fruits, followed by leafy greens. Hit pulse to get things mixed, then blend on high for 30-60 seconds, or until smooth.
1) Super-Antioxidant Smoothie
- 1/4 cup fresh pomegranate juice (1 fruit, juiced)
- 1 banana, peeled
- 3.5 ounces of frozen açaí berry puree
- 1/4 cups frozen wild blueberries
- 2 cups baby spinach or chard, chopped
- 2-4 ounces of filtered water if needed
2) Mango-Berry Smoothie
- 1 mango, peeled and pitted
- 1/2 cup wild blueberries, fresh or frozen
- 2 to 3 handfuls of fresh baby spinach
- 1/4 cup goji berries, soaked for 20 minutes
- 1 tablespoon cacao powder (optional)
- 4 to 6 ounce of filtered water
3) Mango-Grape with Açaí Smoothie
- 1 mango, peeled and pitted
- 1/4 cup red grapes
- 1 serving of frozen açaí berry
- 2 cups romaine or green leaf lettuce, chopped
- 2 ounces filtered water if needed
4) Red Grape and Fig
- 2 fresh figs
- 1/2 cup red grapes
- 1-2 large handfuls fresh kale
- 1 banana, peeled
- 4-6 ounces filtered water
5) Red Grape and Antioxidant Berry Smoothie
- 3.5 ounces frozen açaí berry puree (or 1 cup frozen blueberries)
- 1 large apple, cored
- 2 small handfuls of fresh baby spinach
- 4-6 ounces of water
1 – Nutrition to Reduce Cancer Risk. (2011)
2 – Bingham, S., Day, N., Luben, R., Ferrari, P., Silmani, N., Norat, T., & et al. (2003, May). Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. The Lancet, 361, 1496-1501.
3 – Waldecker, M., Kautenburger, T., Daumann, H., Veeriah, S., Will, F., Dietrich, H., & et al. (2008, April). Histonedeacetylase inhibition and butyrate formation: Fecal slurry incubations with apple pectin and apple juice extracts. Nutrition, 24(4), 366-374. doi:10.1016/j.nut.2007.12.013.
4 – Monneret, C. (2007, April). Histone deacetylase inhibitors for epigenetic therapy of cancer. Anitcancer Dugs, 18(4), 363-370. PMID:17351388.
5 – Vanhoutvin, S., Troost, F., Hamer, H., Lindsey, P., Koek, G., Jonkers, D., & et al. (2009, August). Butyrate-induced transcriptional changes in human colonic mucosa. PloS One, 4(8), e6759. PMID:19707587.
6 – Lupton, J. (2004, Feb.). Microbial Degradation Products Influence Colon Cancer Risk: the Butyrate Controversy. Journal Nutrition, 134(2), 479-482.
7 – Deneo-Pellegrini, H., De Stefani, E., & Ronco, A. (1996). Vegetables, fruits, and risk of colorectal cancer: a case-control study from Uruguay. Nutrition and Cancer, 25(3), 297-304. PMID:8771572
8 – Zhang, C., Ho, S., Chen, Y., Fu, J., Cheng, S., & Lin, F. (2009, July). Greater vegetable and fruit intake is associated with a lower risk of breast cancer among Chinese women. International Journal of Cancer, 125(1), 181-188. PMID:19358284
9 – Jung, K., Wallig, M., & Singletary, K. (2006, Feb.). Purple grape juice inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumorigenesis and in vivo DMBA-DNA adduct formation. Cancer Letters, 233(2), 279288. PMID:15878797
10 – Thompson, L., Chen, J., Li, T., Strasser-Weippl, K., & Goss, P. (2005, May). Dietary Flaxseed Alters Tumor Biological Markers in Postmenopausal Breast Cancer. Clinical Cancer Research, 11, 3828. doi: 10.1158/1078-0432.CCR04-2326.
11 – Rashidkhani, B., Lindblad, P., & Wolk, A. (2005, Jan.). Fruits, vegetables and risk of renal cell carcinoma: a prospective study of Swedish women. International Journal of Cancer, 113(3), 451-455. PMID:15455348.
12 – Shankar, S., Singh, G., & Srivastava, R. (2007, Sept.). Chemoprevention by resveratrol: molecular mechanisms and therapeutic potential. Frontiers In Bioscience, 12, 4839-4854. PMID:17569614.
13 – Aggarwal, B., Bhardwaj, A., Aggarwal, R., Seeram, N., Shishodia, S., & Takada, Y. (2004, Sept.-Oct.). Role of Resveratrol in Prevention and Therapy of Cancer: Preclinical and Clinical Studies. Anticancer Research, 24(5A), 27832840.
14 – Gerhauser, C. (2008). Cancer Chemopreventive Potential of Apples, Apple Juice, and Apple Components. Planta Medica, 74(13), 1608-1624. DOI: 10.1055/s-00281088300.
15 – Keck, A., & Finley, J. (2004, March). Cruciferous Vegetables: Cancer Protective Mechanisms of Glucosinolate Hydrolysis Products and Selenium. Integrative Cancer Therapies, 3(1), 5-12. doi: 10.1177/1534735403261831.
16 – Khan, N., Afaq, F., & Mukhtar, Hasan. (2008, March) Antioxidants & Redox Signaling, 10(3): 475-510. doi:10.1089/ars.2007.1740.
17 – Laboratory and clinical studies of cancer chemoprevention by antioxidants in berries. (2008). Carcinogenesis, 29(9), 1665-1674. doi: 10.1093/carcin/bgn142.
18 – Zhang, Z., Knobloch, T., Seamon, L., Stoner, G., Cohn, D., Paskett, E., & et al. (2011). A black raspberry extract inhibits proliferation and regulates apoptosis in cervical cancer cells. Gynecologic Oncology. doi:10.1016/j.ygyno.2011.07.023.
19 – Seeram, N., Adams, L., Zhang, Y., Lee, R., Sand, D., Scheuller, H., & et al. (2006). Blackberry, Black Raspberry, Blueberry, Cranberry, Red Raspberry, and Strawberry Extracts Inhibit Growth and Stimulate Apoptosis of Human Cancer Cells In Vitro. Journal of Agricultural and Food Chemistry, 54(25), 9329-9339. doi:10.1021/jf061750g.
20- Adhami, V., Khan, N., & Mukhtar, H. (2009, November). Cancer Chemoprevention by Pomegranate: Laboratory and Clinical Evidence. Nutrition and Cancer, 61(6), 811-815. doi:10.1080/01635580903285064.
21 – Lansky, E., & Newman, R. (2007, January). Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. Journal of Ethnopharmacology, 109(2), 177-206. doi:10.1016/j.jep.2006.09.006.
22 – Malik, A., Afaq, F., Sarfaraz, S., Adhami, V., Syed, D., & Mukhtar, H. (2005, October). Pomegranate fruit juice for chemoprevention and chemotherapy of prostate cancer. PNAS, 102(41), 14813-14818. doi:10.1073/pnas.0505870102.
23 – Pomegranate Extract in Treating Patients With Rising Prostate-Specific Antigen Levels After Surgery or Radiation Therapy for Localized Prostate Cancer. (2011).
24 – Duke University Medical Center (2007, June 4). Flaxseed Stunts The Growth Of Prostate Tumors. ScienceDaily.
25 – Roberts, R., Green, J., Lewis, B. (2009, Mar.-Apr.). Lutein and zeaxanthin in eye and skin health. Clinics in Dermatology, 27(2), 195-201. doi:10.1016/j.clindermatol.2008.01.011.
26 – Afaq, F., & Mukhtar, H. (2011). Botanical Antioxidants for Skin Protection: An Overview. Nutrition For Healthy Skin, Part 2, 51-63. doi:10.1007/978-3-642-12264-4_5.