On colorectal adenomas

Men who consume yogurt at least twice a week suffer statistically significantly less from colorectal adenomas than those who never eat yogurt.

Regular yogurt consumption lowers the risk of colorectal cancer precursors in men

Men who consume yogurt at least twice a week suffer statistically significantly less from colorectal adenomas than those who never eat yogurt.

The reduction in risk is much more evident when:

• The larger the adenoma;
• The more pronounced its potential malignancy;
• The more critical its histology in relation to carcinogenesis;
• Its proximal its position is in the large intestine

...as based on the observations of the study’s findings image below. Note that women, on the other hand, do not benefit from eating yogurt (source 1).

In figure 1, we can observe an odds ratio and 95% confidence interval of risk reduction through yogurt consumption in men. We can observe A: Colorectal adenomas according to subtypes in HPFS; B: Only conventional adenomas according to findings location in HPFS (according to source 1).

These are the results of a prospective evaluation of data from 32,606 male participants in the Health Professionals Follow-up Study (HPFS) and 55,743 female participants in the Nurses' Health Study (NHS) who underwent an endoscopy of the lower abdomen between 1986 and 2012 (source 1).

Data from the treasure trove of large longitudinal studies

The authors of the current study by Xiaobin Zheng from the Department of Public Health at Washington University School of Medicine in St. Louis, Missouri, USA and Sun Yat-sen University in Guangzhou, China, see their study as a response to the search for modifiable risk factors for colorectal adenomas. Scientists are calling for this to be done as a matter of urgency for the successful prevention of colorectal cancer (source 2)

For their study, the researchers drew on the data collections of the HFPS and NHS, which were collected prospectively over decades. In this case, the data collections of the two longitudinal studies allow rapid conclusions to be drawn on suspected risk factors without having to rely on the years of preparatory work for new prospective studies. Among other things, the two studies contain information on the participants' yogurt consumption, which was recorded every four years and is now being evaluated. The current evaluation was based on 5,811 cases of colon adenomas in men and 8,116 cases of colon adenomas in women identified among HPFS and NHS participants for the years 1986 to 2012.

Mechanisms of action not yet determined

According to the scientists, yogurt is recommended in US diet guidelines as a fat-free or low-fat milk product (source 3). However, the average yogurt consumption in the USA is low, although yogurt appears to be able to reduce the risk of at least conventional colorectal adenomas. As a potential protective mechanism of yogurt, it would be discussed that yogurt probiotics such as Lactobacillus bulgaris and Streptococcus thermophilus can reduce the concentration of carcinogens in the intestine. Such carcinogens include nitroreductase, fecal-activated bacterial enzymes and/or soluble fecal bile acids. In addition, an anti-inflammatory effect and a promotion of the barrier function in the intestine by yogurt would be considered.

From the latter presumed yogurt effect, the authors also derive the initially surprising observation that only men benefited from increased yogurt consumption. According to the authors of the study, male adenoma patients suffered from increased permeability of their intestines compared to affected women. The researchers suspect that yogurt could counteract this and thus explain the gender-specific effect.

The scientists attribute the more pronounced protective effect against adenomas in the proximal instead of the distal colon, to the distally decreasing pH in the intestine, which leads to increasingly poor environmental conditions for yogurt probiotics.

Sources:
1. Xiaobin Zh, et al. Yogurt consumption and risk of conventional and serrated precursors of colorectal cancer. Well Published Online First: 17 June 2019. doi: 10,1136/gutjnl-2019-318374
2. Davenport JR, et al. Modifiable lifestyle factors associated with risk or sessile serrated polyps, conventional adenomas and hyperplastic polyps. Good. 2018; 67: 456-465. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5432410/pdf/nihms836935.pdf
3. U.S. Department of Health and Human Services and U.S. Department of Agriculture. Department of Agriculture. 2015 - 2020 Dietary Guidelines for Americans. 8th Edn, 2015. https://health.gov/dietaryguidelines/2015/guidelines/