Composed: May 3, 2023
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Colon Cancer - what does the research say about meat?
I have a pretty strong family history of colon cancer. I lost my brother to colon cancer that metastasized to his liver. This was part of a genetic condition, Familial Adenomatous Polyposis (FAP), which I do not appear to have inherited. Still, it is a risk factor for me and one that I have discussed at length with gastroenterologists over the years and something I take into consideration when deciding what and how to eat.
I'm making this post to share my story, thought process, and the reasons I've made the decisions I have about what and how to eat. This isn't advice for anyone.
I don't seem to have inherited FAP or Attenuated FAP, a variant characterized by later onset. Still, medical professionals take the fact that I lost a sibling to colon cancer seriously and have advised me based upon that information to have colonoscopies much earlier than is typically recommended for people who don't have a family history of colorectal cancer. Regular screenings are recommended beginning at age 45.
As a teenager, I was a vegetarian. As a young adult, I ate a pretty standard Western diet, consisting of plenty of fruits, veggies, grains, some meat, plant based oils, and various forms of sugar (cane sugar, beet sugar, etc.). I ate pretty healthy but also indulged in sweets and other baked goods.
I had my first colonoscopy sometime in my 20s. I had one polyp, which was removed, tested, and came back non-cancerous (benign). In subsequent screenings, the occasional polyp was found, removed, tested, and, thankfully, they all came back benign.
In my mid 30s I began following a ketogenic way of eating, which consisted of meat, animal-based and plant-based fats (avocado oil, olive oil, coconut oil), low-starch/low-sugar veggies, berries, and low-carb dairy. I was now eating way more meat than I ever had before and had no more polyps.
In my late 30s, I made a switch to an animal based (carnivore) way of eating that eliminated most or all of the plant foods I'd been consuming on a ketogenic way of eating. And, again, I had no polyps.
As I aged, I had less polyps as my diet trended more toward consumption of meat and as I decreased or eliminated plants from my diet. In three more years, I'll be the age they recommend everyone start getting screenings for colorectal cancer.
What does the research say?
There certainly is research that states that red meat consumption increases risk for colorectal cancer.
The majority of the data I sourced found a correlation between red meat consumption and risk for colorectal cancer. Some research identified possible mechanisms. These mechanisms included carcinogens in meat, such as N-nitroso compounds (NOC) and heterocyclic aromatic amines, and the endogenous compound, heme iron.
An assessment of more than 800 epidemiological studies that investigated the association of cancer with consumption of red meat or processed meat in many countries, from several continents, with diverse ethnicities and diets classified consumption of red meat as "probably carcinogenic to humans". However, no research was able to prove that consumption of red meat (or any meat) led to increased deaths. It only spoke to an association.
A review of mechanistic evidence for heme in the context of risk assessment methodology makes a few important points that cast doubt on some of these assertions:
The evidence from in vitro studies utilized conditions that are not necessarily relevant for a normal dietary intake and thus do not provide sufficient evidence that heme exposure from typical red meat consumption would increase the risk of colon cancer.
Animal studies utilized models that tested promotion of preneoplastic conditions utilizing diets low in calcium, high in fat combined with exaggerations of heme exposure that in many instances represented intakes that were orders of magnitude above normal dietary consumption of red meat.
Finally, clinical evidence suggests that the type of NOC found after ingestion of red meat in humans consists mainly of nitrosyl iron and nitrosothiols, products that have profoundly different chemistries from certain N-nitroso species which have been shown to be tumorigenic through the formation of DNA adducts.
In conclusion, the methodologies employed in current studies of heme have not provided sufficient documentation that the mechanisms studied would contribute to an increased risk of promotion of preneoplasia or colon cancer at usual dietary intakes of red meat in the context of a normal diet.
A prospective cohort study published in 2022, using data from participants with stage III colon cancer enrolled in the Cancer and Leukemia Group B (CALGB 89803/Alliance) trial between 1999 and 2001 concluded that:
Post diagnosis intake of unprocessed red meat or processed meat was not associated with risk of recurrence or death among patients with stage III colon cancer.
I will reiterate that this is not advice for anyone. This is simply a sharing of my experience and what led me to try the things I have. Everyone should make their own informed decisions based upon their own review of the available research, their own risk factors (such as family history), and discussions with their doctors, as appropriate. For me, the fact that I've produced less polyps as I've aged suggests to me that what I'm doing is contributing to my own colon health.
One last note. For anyone who has ever had a colonoscopy, you may know that the "prep" is not a fun process. It usually consists of a few days of medically prescribed fasting followed by the consumption of oral laxatives in a bowel prep kit. The prep process is uncomfortable as it causes your body to evacuate your bowels. It can cause some stomach cramping and/or bloating and it requires a lot of time in the bathroom. The prep I have done on an animal-based (carnivore) diet was the easiest. I had the least discomfort and my bowels emptied quickest.