Want to know what I find fun? Don’t laugh, but I think it is very fun to review new groundbreaking research right when it comes out.

For example, I still remember in grad school when the article came out about social networks and obesity (Christakis & Fowler, 2007). It was this really large (~12K people) study published in the New England Journal of Medicine where they looked at risk of developing obesity over several years using data from the Framington Heart Study. In short, it showed that your risk of developing obesity was 57% if a friend developed obesity, even if the friend lived far away, and this risk was significantly more if they were the same sex. Surprisingly, risk from a friend becoming obese was stronger than if a sibling, spouse or neighbor became obese during the same time period.

It was fun to review this new data and posit reasons for these social network connections, and discuss the potential public health implications (for example, are there ways we can change this and more positively utilize social networks for healthy behavior change? Perhaps a future blog post…).

But do you you know what is much less fun? Finding out that despite spending about 16 years formally and informally studying nutrition, wellness, and lifestyle interventions, that I somehow missed a entire large body of research.

Four weeks ago I started taking an online course through Cornell University on Plant-based Nutrition. Through that course, I have learned that there is a robust body of research dating back to the 1970s linking animal protein to the development of cancer. Were you guys aware of this?

I can’t help but wonder, as someone invested in research related to health, wellness, and behavior changes, how the heck did I miss this? If you have any ideas, please let me know.

In the About This Site page, I did start with this quote:

It has been suggested that it can take up to 17 years for research to reach real-world practice (Balas & Boren, 2000).

I guess sometimes it can take considerably longer than 17 years, more like 40. Regardless, if you are anything like me, some of the information below may be news to you.

Back in the 1970s, Dr. T Colin Campbell, a nutrition researcher at Cornell University, was noticing that liver cancer in children in the Philippines was more likely to occur in children who consumed more animal protein. He then discovered that another research group had found this relationship in a study published in 1968, where rats given a diet of 5% animal protein had a much lower risk of tumor development after exposure to a cancer-causing chemical (0/12 rats developed tumors), when compared to rats fed a diet of 20% animal protein (30/30, or 100% of those rats developed tumors) (Madhavan & Gopalan, 1968).

Dr. Campbell went on to replicate these findings multiple times in his lab, and also showed that pre-cancerous cells (indicative of future tumor development and cancer) could be increased or decreased, based on switching rats from a diet of 5% protein to 20% protein (Youngman & Campbell, 1991; Youngman & Campbell, 1992; Dunaif, & Campbell, 1987). So not only was animal protein content directly linked to cancer development, but by reducing animal protein, pre-cancerous growth would quickly shrink, even after just 3 weeks of the low protein diet.

Protein used in these studies was casein, a common protein in milk and other dairy products. This effect was only present when animal protein was used, not plant protein.

Following these studies, Dr. Campbell and colleagues wanted to look at these relationships in humans, and conducted arguably the most robust study of nutrition in a large epidemiological study called The China Project or The China Study (see book summarizing the entire project: Campbell & Campbell, 2006).

China was ideal to study at this time (around 1983) because:

• It had a huge population and about 880 million people, 96% of their population were studied.
• The diets of the Chinese were much more plant-based than those in the west, allowing researchers to study a plant-based eating pattern on a larger scale. That is, not enough people in the US were eating this way so it would have been very challenging to study in a meaningful way.
• The Chinese very rarely migrated within their country, and 90%-95% of people in rural China never left the area they were born, making their eating patterns easier to study and accurately link to disease risk.
• Food systems were highly localized and food patterns varied a lot from one region to another and were rarely transported to other regions or villages, lending more confidence to the study conclusions.
• There was little genetic variation between subjects, suggesting that changes in disease risk were likely due to diet, not genetics.

Summary of Main Findings of The China Study:

• Cancer rates were very different from one part of the country to another, sometimes up to a 12-fold difference, which is much higher than you see in Western countries (usually only a 1:2 fold difference at most). This also suggests that disease risk is more likely due to environmental factors (diet, or otherwise) versus genetics.
• Higher fat and animal protein (e.g., meat, dairy, eggs) was linked to higher cancer rates across a range of cancers.
• Higher fiber diets were linked to lower rates of cancers such as colon cancer.

Summarizing all the research beyond these two sets of studies is beyond the scope of this post, but there is more data supporting this link that I ever realized and the effects are not small. I was aware that fruits and vegetables and a “generally healthy diet” were associated with lower cancer risks, but I had no idea animal protein could explain so much of the relationship.

When I started this blog and I told you in my About Me section that I am not one to endorse any one specific eating pattern. I sometimes eat vegan, sometimes vegetarian, and I sometimes eat hot dogs, Italian sandwiches, and dairy. My goal is never to tell you what is right for you, but instead to just bring you the evidence and let you choose for yourself.

We have learned recently that several of my loved ones have very strong genetic risks for cancer, so this information seemed even more relevant. Although cancer is terrifying, I found this information empowering, as so much of the data suggests that we have a lot of control over our cancer risk via our diet. Our genes are not our destiny.

As of now, I don’t think I will ever be fully vegan but did this information make me seriously reconsider my animal protein intake and how we eat as a family?

Most certainly yes.

I would love to hear your reactions to this.

Was this information new to you? What do you think about it? Does it make you reconsider your choices?

References

Campbell, T. & Campbell, T. C. (2006). The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss, and Long-term Health.

Christakis, N. A. & Fowler, J. H. (2007). The spread of obesity in a large social network over 32 years. New England Journal of Medicine, 357, 370-379.

Dunaif, G. E. & Campbell, T. C. (1987). Dietary protein level and aflatoxin B1-induced preneoplastic hepatic lesions in the rat. The Journal of Nutrition, Volume 117, Issue 7, 1298–1302.

Madhavan, T. V. & Gopalan, C. (1968). The effect of dietary protein on carcinogenesis of aflatoxin. Archives of Pathology & Laboratory Medicine, 85, 133-137.

Youngman, L.D., & Campbell, T. C. (1992). Inhibition of aflatoxin B1-induced gamma-glutamyl transpeptidase positive (GGT+) hepatic preneoplastic foci and tumors by low protein diets: evidence that altered GGT+ foci indicate neoplastic potential. Carcinogenesis, 13: 1607–1613.

Youngman, L. D., & Campbell, T. C. (1991). High protein intake promotes the growth of preneoplastic foci in Fischer #344 rats: evidence that early remodeled foci retain the potential for future growth. The Journal of Nutrition, 121.