Someone asked me recently should they eat fermented foods if they have had cancer.  The question arose because cancerous cells use sugar and sugar is also involved in fermentation.

Fermentation and sugar

Fermentation can be initiated using bacteria or yeasts.  Bread, beer and wine are all examples of fermentation using yeast.  Yogurt, kimchi, cheese, pickles, kefir, sauerkraut are examples of bacteria-based fermentation.

Where bacteria are used, they feed on the sugars and starches in the food to create lactic acid, which is a preservative.  This is why fermentation has been used for centuries to preserve food.  Not only does it preserve, but it also keeps essential vitamins, fatty acids and probiotics in the food.

Fermented foods and cancer

In answer to the question, therefore, the sugar initially present has been converted by the bacteria.  As a result, in theory fermented foods can be eaten if someone has had cancer and in fact show some benefit.  As always, however, there is a caution with this statement – studies are few and some are either in vitro (testtube) or on animals.  In addition, as we know, cancer is a universal term and specific organs manifest cancer in different ways.  It is important, therefore, when choosing a fermented food that you look at studies specific to your particular illness.

Here is some general information to get you going.

Specific fermented foods

Pickled and salted foods are fermented, but should be avoided.  There are a number of Japanese studies on salted fish, all of which conclude that there is an association between dietary intake and nasopharyngeal carcinoma[1],[2].  The main reason for this is the presence of salt, rather than the fermentation process.  Similarly, a systematic review and meta-analysis of English and Chinese literature in relation to gastric cancer[3] found a 50% increased risk from pickled foods.

Other fermented foods included yogurt, kefir, kimchi and sauerkraut.

Research on sauerkraut is quite slim and is on animals or in vitro, rather than on humans.  Indications are that it does have an anti-cancer effect (as does cabbage and all cruciferous vegetables).  There is one caution however.  Some people have a reaction to sauerkraut, resulting in diarrhea and loose stool, so use with caution initially.

Peñas et al, 2010[4], showed that low-salted sauerkraut produced with the bacteria, L. mesenteroides provided highly beneficial antioxidant and anticarcinogenic compounds.  Szaefer et al[5], 2010, also found that raw cabbage and sauerkraut juices may exert an anticarcinogenic activity on liver and kidney tissue, but at different times and in different ways.

Kimchi also has not been widely researched, but again has positive indications for cancer.  There is some research showing that it is effective against colorectal cancer.  Kim et al, 2014[6], found that kimchi suppressed colon cancer in mice and that a form of kimchi called “anti-cancer kimchi” was particularly potent.

Kefir has been widely researched.  Leite et al, 2013[7] outline kefir’s anti-tumour effect, its ability to cause cell apoptosis (cell death) and also its role as an antioxidant.  Similarly, Bourrie et al, 2016[8], outline further studies on kefir’s anti-tumour activity and its ability to cause death of cancer cells.  Again a word of caution here.  Some of these studies were on mice and with specific cancers, but it is certainly worth researching further depending on your cancer.

Cultured yogurts, will be the subject of a separate blog.  A large cohort study in the Netherlands found a weak association between fermented dairy and improvements in bladder cancer and colorectal cancer[9], [10].   And a Japanese study by Kawakita et al, 2012[11] found a high intake of yoghurt may lower the risk of developing upper aerodigestive tract cancer in a Japanese population.

Finally, Tagaki et al, 2015[12] found that fermented soy milk with probiotics had the potential to be useful in reducing the risk of breast cancer.

In conclusion, some fermented foods may be useful in some cancers, but you need to carefully research.   If using probiotic yogurt look for the number of bacteria.  Many of studies use yogurt containing at least a billion bacteria.  Most yogurt on sale has this quantity, but be cautious and avoid those laden with sugar!  As always, feed your body with the most nutritious food you can find for optimum health.  For more information contact us at




[1] Yu et al, Cantonese-style salted fish as a cause of nasopharyngeal carcinoma: report of a case-control study in Hong Kong, Cancer Research, 1986, Feb;46(2):956-61,

[2] Jia et al, Traditional Cantonese diet and nasopharyngeal carcinoma risk: a large-scale case-control study in Guangdong, China, BMC Cancer, 2010, DOI: 10.1186/1471-2407-10-446,
[3] Ren et al, Pickled Food and Risk of Gastric Cancer—a Systematic Review and Meta-analysis of English and Chinese Literature, Cancer Epidemiology Biomarkers & Prevention, June 2012, DOI: 10.1158/1055-9965.EPI-12-0202,

[4] Peñas et al, Chemical evaluation and sensory quality of sauerkrauts obtained by natural and induced fermentations at different NaCl levels from Brassica oleracea Var. capitata Cv. Bronco grown in eastern Spain. Effect of storage. J Agric Food Chem. 2010 Mar 24;58(6):3549-57. doi: 10.1021/jf903739a,

[5] Szaefer et al, Modulation of carcinogen metabolizing cytochromes P450 in rat liver and kidney by cabbage and sauerkraut juices: comparison with the effects of indole-3-carbinol and phenethyl isothiocyanate. Phytotherapy Research, 2012, Aug;26(8):1148-55. doi: 10.1002/ptr.3692,

[6] Kim et al, Kimchi Protects Against Azoxymethane/Dextran Sulfate Sodium–Induced Colorectal Carcinogenesis in Mice, Journal of Medicinal Food, 2014,

[7] Leite et al, Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage, Brazilian Journal of Microbiology, 2013,

[8] Bourrie et al, The Microbiota and Health Promoting Characteristics of the Fermented Beverage Kefir, 2016, Frontiers in Microbiology,

[9] Kampman et al, Fermented dairy products, calcium, and colorectal cancer in The Netherlands Cohort Study, Cancer Research, 1994,

[10] Keszei et al, Dairy intake and the risk of bladder cancer in the Netherlands Cohort Study on Diet and Cancer, American Journal of Epidemiology, 2010,

[11] Kawakita et al, Inverse association between yoghurt intake and upper aerodigestive tract cancer risk in a Japanese population, European Journal of Cancer Prevention, September 2012 – Volume 21 – Issue 5 – p 453–459

[12] Tagaki et al, Possibility of Breast Cancer Prevention: Use of Soy Isoflavones and Fermented Soy Beverage Produced Using Probiotics, International Journal of Molecular Science, 2015,




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