Epidemiologic Studies

A meta-analysis of 61 studies including more than 1.9 million participants found that in the cohort studies, intake of fermented dairy significantly decreased the risk of cancer (odds ratio [OR], 0.86; 95% confidence interval [CI], 0.80-0.92).8 Yogurt significantly decreased cancer risk in the cohort studies (OR, 0.81; 95% CI, 0.74-0.88). When stratified by cancer type, fermented dairy significantly decreased the risk of bladder, colorectal, and esophageal cancers. Another meta-analysis, however, which included 11 cohort studies and over 700,00 participants, found no association between yogurt or cheese intake and cancer-specific mortality.9 Similarly, fermented food intake, which was primarily fermented dairy, was not associated with all-cause mortality or cancer-specific mortality in a large cohort study.10

Many epidemiologic studies focused on the association between fermented dairy intake and colorectal cancer (CRC). An early study published in 1994 reported a weak association between fermented milk intake and decreased risk of CRC, but the results were not significant.11 Since then, a large prospective cohort study with 12 years of follow-up found that after adjusting for variables such as energy intake, body mass index, smoking, education, and intake of animal fat, red meat, or alcohol, high levels of yogurt consumption significantly decreased the risk of CRC compared with low levels of consumption (hazard ratio [HR], 0.65; 95% CI, 0.48-0.89).12 A meta-analysis, however, found that high cheese intake was not significantly associated with CRC incidence.13

The effects of fermented dairy intake on other cancers was also mixed. A meta-analysis of epidemiologic studies found that yogurt consumption modestly, but significantly, decreased the risk of breast cancer (risk ratio [RR], 0.91; 95% CI, 0.83-0.99).14 A low level of fermented milk consumption decreased the risk of bladder cancer (HR, 0.71; 95% CI, 0.56-0.91), but a higher level of consumption did not.15

Related Articles

Fermented dairy products such as yogurt, cheese, and/or cottage cheese was not associated with risk of endometrial, ovarian, gastric, pancreatic, lung, or liver cancers.16-21 Cheese, however, did increase the risk of liver cancer in a European cohort study (HR, 1.56; 95% CI, 1.02-2.38).20

Treatment Toxicities

There have been studies of whether kefir can reduce chemotherapy-induced toxicities or discomfort. In one study, kefir oral lavage and ingestion was compared with an oral rinse of 0.09% NaCl for the prevention of 5-fluorouracil–induced mucositis.22 There was no difference in incidence of mucositis or the presence of proinflammatory cytokines.

In another randomized study, kefir consumption increased the number of gastrointestinal complaints during CRC treatment, but also decreased sleep disturbance compared with control.23

Conclusions

In vitro and animal studies suggest that fermented dairy, particularly kefir, may have anticancer properties. In-human studies are needed to determine if these findings translate to humans.

Epidemiologic data are mixed regarding the ingestion of fermented dairy products for chemoprevention. Although fermented dairy intake overall may have a protective effect and several studies suggested that yogurt intake may reduce the risk of CRC and breast cancer, other studies found no association between fermented milk or cheese consumption and risk of cancer.

Taken together, these data suggest that although there is a theoretical anticancer benefit to consuming fermented dairy, there are no definitive data to indicate that fermented dairy products prevent cancer in humans, but yogurt may provide a preventive benefit for some cancers.

References

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