January 29, 2020
Cancer Deaths are Decreasing. The real reason might be surprising.
Cancer death rates have fallen 27% since Dr. Bloom and I graduated from the National College of Naturopathic Medicine in 1991. According to the American Cancer Society’s website, “The death rate from cancer in the US has declined steadily over the past 25 years,…. As of 2016, the cancer death rate for men and women combined had fallen 27% from its peak in 1991. This decline translates to about 1.5% per year and more than 2.6 million deaths avoided between 1991 and 2016.” 
The largest drop was between 2016 and 2017. During this period cancer mortality rates dropped 2.2%. The expert view is that this drop is driven by “accelerating declines in lung cancer mortality.” 
The numbers really are impressive: Lung cancer death rates declined 48% from 1990 to 2016 among men and 23% from 2002 to 2016 among women. (The differences reflect historical patterns in tobacco use, where women began smoking in large numbers many years later than men and then were slower to quit.)
While breast cancer deaths dropped by 40%, prostate cancer by 51% and colorectal death by 53% over a similar time period, lung cancer kills more people than all three of these other cancer types combined so has the biggest impact on overall statistics.
The official explanation for the decrease in lung cancer deaths is because of decreased smoking.
There is another possible explanation to the changes seen in lung cancer rates besides a decrease in smoking. It has to do with the surge in popularity of yogurt and was brought to our attention by a paper published in JAMA Oncology last October.
The authors, researchers at Vanderbilt University Medical Center, pooled together data from 10 prospective cohorts involving 1,445,850 adults from studies that were conducted in the United States, Europe, and Asia. They calculated hazard ratios for lung cancer risk associated with dietary fiber and yogurt intakes. They report that high intakes of dietary fiber or yogurt were individually associated with reduced risk of lung cancer, independent of all known risk factors. A potential synergistic association of fiber and yogurt consumption with lung cancer risk was also observed. By fiber, think fruit. Those study participants with the highest yogurt and fiber consumption had a 33% reduced lung cancer risk as compared to the group who did not eat yogurt and consumed the least amount of fiber. 
How could something so simple make such a large impact? Yogurt has been touted as a health food that would increase longevity for a century. Perhaps there is some truth in the advertising? A 2017 paper suggested that the combination of yogurt and fruit might have synergistic action because the yogurt supplies probiotic bacterial cultures and the fruit has prebiotic properties providing nondigestible fiber substrates that feed the bacteria. “Combining the intake of yogurt and fruit could provide probiotics, prebiotics, high-quality protein, important fatty acids, and a mixture of vitamins and minerals that have the potential to exert synergistic effects on health.” 
In recent years attention in cancer research has turned toward the gut biome, the population of microorganisms inhabiting the human gut, and its role providing protection against cancer. Recent focus has been on the lung biome, the bacterial population that transfers from the upper GI tract into the lungs. While our understanding of these interactions is still incomplete, the data from the Vanderbilt study, that something as simple as eating yogurt, affects lung cancer incidence so much, suggests these investigations are on the right track.
Consumption of dairy foods has declined in recent decades, dropping from 339 pounds/per person per year in 1970 to 276 pounds in 2012. During the same period yogurt consumption has gone from negligible to about 15 pounds per year. Yogurt consumption has more than doubled, from 6.5 pounds in 2000 to almost 15 pounds in 2014. 
Back in 1970 hardly anyone ate yogurt; consumption was described as negligible. I can’t even find statistics from back then. 
The French population apparently consumes the most yogurt averaging, over 21 kilo per year.
Out of curiosity which countries have the highest incidence of lung cancer? France doesn’t show up on the list. It doesn’t take fancy statistical analysis to notice that countries that consume more than about 15 pounds of yogurt per year, don’t make it to the top ten list of lung cancer incidence.
So, while reductions in smoking likely play a major role in decreasing lung cancer deaths in the US, at the same time, we should give some credit to yogurt’s increasing popularity as well.
 Yang JJ, Yu D, Xiang YB, et al. Association of Dietary Fiber and Yogurt Consumption With Lung Cancer Risk: A Pooled Analysis. JAMA Oncol. 2019 Oct 24.
 Fernandez MA, Marette A. Potential Health Benefits of Combining Yogurt and Fruits Based on Their Probiotic and Prebiotic Properties. Adv Nutr. 2017 Jan 17;8(1):155S-164S.
 Maddi A, Sabharwal A, Violante T, et al. The microbiome and lung cancer. J Thorac Dis. 2019 Jan;11(1):280-291.