Strawberries found to retard breast, lung, prostate, and liver cancers; Organic berries slow growth most strongly; strawberries also found to inhibit inflammation
by Craig Weatherby
The fragrant, succulent fruit that tastes so good with shortcake may also help the body in its fight to make short work of the most common cancers.
New findings show that strawberries can slow the growth of human breast, and colon cancers sharply, at least in cell tests conducted outside the body.
Researchers at the Swedish University of Agricultural Sciences found that on average, strawberry extracts reduced growth of breast cancer cells by 53 percent and reduced growth of prostate cancer cells by 43 percent (Olsson ME, 2006).
These new findings confirm and expand on the results of three studies published in 2003 and 2005, which show that strawberry extracts can reduce the growth rate of human lung and liver cancer cells, and mouse skin cancer cells, to substantial extents (Meyers KJ 2003, Ramos S, 2005, Wang Y, 2005).
Organic cultivation and particular vitamin C profiles enhance berries’ anti-cancer effects
The Swedes tried extracts from five different strawberry cultivars, and tested organically and conventionally raised examples of each to compare their anti-cancer powers.
Sure enough, extracts from organically grown strawberries blocked cancer growth better than correspondingly strong extracts of conventionally grown berries.
This advantage was seen in tests on both breast and prostate cancer cells, and was especially apparent when they were exposed to the most concentrated strawberry extracts.
Surprisingly, evidence from the recent rash of strawberry studies indicates that the potency of each cultivar’s anti-cancer power is not closely related to its levels of antioxidant polyphenols: the compounds associated with many fruits' anti-cancer effects.
The Swedish results suggest that the vitamin C in a strawberry is needed to release the full preventive power of its polyphenol antioxidants, which are known to exert anti-cancer effects.
In their study, the berries highest in vitamin C blocked breast cancer growth the best, regardless of their polyphenol content, which was generally high in all the strawberries, but varied significantly among cultivars.
And the reason why organic berries were the top anti-cancer performers may also be related to their vitamin C profile. The Swedes' results show that berries with higher bodily ratios of vitamin C (ascorbate) to a modified form (dehydroascorbate)—a characteristic common to all the organic berries tested—had the greatest growth-reducing impact on prostate cancer cells.
Interestingly, the authors of another strawberry study (Meyers KJ, 2003) found significant differences in antioxidant levels and profiles among the eight cultivars they tested, but found no relationship between antioxidant content and anti-cancer activity. In light of the recent Swedish findings, these differences may, in hindsight, be attributable to differing levels of vitamin C in the various cultivars.
Strawberries turn off cells’ pro-inflammatory, pro-cancer switches
Readers of the several diet and anti-aging bestsellers by Nicholas Perricone, M.D. may recall that pro-oxidant free radicals and the anti-oxidants that neutralize their damaging effects exert opposite influences on genetic switches in our cells that trigger inflammation and also promote cancer.
Many antioxidants are known to shut off the pro-inflammatory genetic switches called AP-1 and NF-kappaB, which are the two top targets of Dr. Perricone’s dietary and nutritional prescriptions.
The findings from a study published last year (Wang Y, 2005) show that strawberry extracts can prevent activation of these pro-inflammatory bad actors and others in mouse skin cells.
As its authors summarized the situation, “…strawberries may be highly effective as a chemopreventive [cancer-preventive] agent that acts by… [suppressing] AP-1 and NF-kappaB activities… and suppressing cancer cell proliferation [spread] and transformation [to more threatening states].”
And what could constitute a more delicious prescription for cancer prevention or amelioration than a handful of these sweet, tangy, intensely flavorful berries?
- Olsson ME, Andersson CS, Oredsson S, Berglund RH, Gustavsson KE. Antioxidant levels and inhibition of cancer cell proliferation in vitro by extracts from organically and conventionally cultivated strawberries. J Agric Food Chem. 2006 Feb 22;54(4):1248-55.
- Meyers KJ, Watkins CB, Pritts MP, Liu RH. Antioxidant and antiproliferative activities of strawberries. J Agric Food Chem. 2003 Nov 5;51(23):6887-92.
- Wang SY, Feng R, Lu Y, Bowman L, Ding M. Inhibitory effect on activator protein-1, nuclear factor-kappaB, and cell transformation by extracts of strawberries (Fragaria x ananassa Duch.). J Agric Food Chem. 2005 May 18;53(10):4187-93.
- Ramos S, Alia M, Bravo L, Goya L. Comparative effects of food-derived polyphenols on the viability and apoptosis of a human hepatoma cell line (HepG2). J Agric Food Chem. 2005 Feb 23;53(4):1271-80.
- Beekwilder J, Hall RD, de Vos CH. Identification and dietary relevance of antioxidants from raspberry. Biofactors. 2005;23(4):197-205.
- Kiss A, Kowalski J, Melzig MF. Induction of neutral endopeptidase activity in PC-3 cells by an aqueous extract of Epilobium angustifolium L. and oenothein B. Phytomedicine. 2006 Mar;13(4):284-9. Epub 2005 Jun 27.
- Seeram NP, Adams LS, Henning SM, Niu Y, Zhang Y, Nair MG, Heber D. In vitro antiproliferative, apoptotic and antioxidant activities of punicalagin, ellagic acid and a total pomegranate tannin extract are enhanced in combination with other polyphenols as found in pomegranate juice. J Nutr Biochem. 2005 Jun;16(6):360-7.