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Abstract
Some studies have suggested chemopreventive effects of kefir, a fermented milk product, on carcinogenesis. The aim of this review study was to evaluate the scientific evidence for effects of kefir on cancer prevention and treatment. We systematically searched for all relevant studies published before June 2015, using PubMed, Google scholar, Cochrane and Science Direct, SID, MedLIb and Srlst databases. Relevant studies were reviewed based on systematic review (PRISMA) guidelines. From a total of 2208 papers obtained at the initial database search, 11 publications including 7in vitro and 4 experimental studies were eligible. In vitro studies on breast, colon, skin and gastric cancers and leukemia cell lines and experimental studies on different sarcomas consistently showed beneficial effects of kefir on cancer prevention and treatment. The results ofthis systematic review suggest that kefir may be associated with cancer prevention and it also has beneficial effects in cancer treatment. This protection may be associated with kefir bioactive components Including peptides, polysaccharides and sphingolipids.
Keywords: Cancer, fermented milk products, kefir, systematic review
Introduction
Cancer· abnormal division and reproduction of cells that can spread throughout the body·1 is a leading cause of death worldwide and the total number of cases is increasing globally.2 A recent analysis estimated 13.2 million deaths and 20.3 million incident cases for cancer in 2030.3 Thus preventive strategies are critical in every cancer control plan.2 Among factors responsible for cancer· it has been estimated that diet accounts for about 20%-30% of all cases worldwide. Several studies support the idea that some dietary components· such as fruits and vegetables· are protective factors against cancer.4 There is also evidence that a diet rich in fermented foods such as fermented milk prodnets may have beneficial properties in reducing risk of some cancers.5-7 Kefir is a type of fermented milk made from adding small cauliflower floret-like grains to pasteurized milk. The grains contain a mixture of yeast and bacteria living in a symbiotic community. This special symbiotic nature makes kefir different from other fermented dairy products such as yogurt. The alleged healthy capabilities of kefir include antifungal and antibacterial properties, benefits for digestive tract and beneficial effects on cholesterol. It has also been found to exert beneficial effects on preventing several types of cancer.8 Anticancer properties of...