Are lifestyle factors increasing rates of early-onset colon cancer?

Are lifestyle factors increasing rates of early-onset colon cancer?

Dr. Talia Henkle
Dr. Talia Henkle

In 10 seconds? Rates of colorectal cancer among people under 50 have shot up in the last thirty years in high-income countries. While the exact causes aren’t clear, researchers suspect the Western lifestyle may be to blame.

So, what exactly is happening? Between 1988-2015, rates of colorectal cancer (CRC) among the under 50s (AKA early-onset CRC) have increased by 63% (From 7.9 to 12.9 per 100,000 people) - and numbers are still on the rise. What's more, is that these cancers tend to be diagnosed at a later stage and have a poorer prognosis than CRC diagnosed in people over the age of 50.

That’s not good. Do we know what’s behind the early onset cases? About 30% of the early-onset CRC cases can be tied to a genetic factor called Lynch syndrome, which is a defect in our cells’ DNA repair processes that leads an individual to have a harder time repairing potentially cancerous mutations. The other 70% of cases have no known genetic cause and are thought to be caused by lifestyle factors–like an unbalanced diet and insufficient exercise.

Is this the dreaded ‘Western lifestyle’? You’ve got that right! Around 50 years ago, the US and other high-income nations shifted to what is referred to as the ‘Western lifestyle’. The Western diet is composed of higher levels of processed meats and sugar (i.e. it includes many foods that are industrially modified from their original sources like those with additives or preservatives). In addition, a high proportion of the population smokes and leads a sedentary lifestyle (Think sports fans whose sports activity is limited to parking their six-packs (of beer) and chips in front of the TV and sitting down for the game). The Nurses’ Health Study II associated the Western diet with higher levels of early-onset CRC. On that note, higher consumption of whole grains (like brown rice and oatmeal) compared to refined grains (like white flour and rice) is associated with a lower risk of early-onset CRC.

Factors that influence the risk of colorectal cancer. Source: Sinicrope FA. N Engl J Med. 2022;386:1547-58

I guess I should start eating healthier… You got that right… again! (I know, it’s a mantra). Eating healthy is always a good idea. But one thing to keep in mind is the fact that cancer usually takes decades to form–that means someone’s level of risk for developing CRC in their 40s might have to do with their diet and lifestyle during childhood and adolescence. To this point, consumption of sugar-sweetened beverages among female adolescents aged 13-18 years increased an individual's risk of developing early-onset CRC by 32% in each increment measured! Similarly, obesity in adolescence also has been correlated with increased risk. That being said, fat around the abdomen, compared to overall body weight, seems to be more influential in increasing risk.

How can my diet cause CRC? In short, it’s hypothesized that the Western diet promotes unhealthy levels of sulfur-metabolizing bacteria, which produce toxins that can damage our DNA, which promotes cancer formation. This train of thought also brings the wide use of antibiotics–which mess with our gut microbiome as well–into question. (Check out an earlier Digest about what the “Iceman’s” gut microbiome has taught us about Western diseases)

What are the signs I might have early onset CRC? Deep breath. Chances are you are FINE. It turns out that symptoms that can indicate CRC, like blood in stool, abdominal pain, and bloating, are relatively common and most frequently associated with non-life-threatening conditions.

So, what can we do? Prevention, prevention, prevention. Due to the increase in cases, the US Preventative Services Task Force changed the recommended age for CRC screening colonoscopy from 50 to 45-49 in 2016. Yet, even among those 50 and older only about 70% of individuals undergo screening. Despite the immense pleasure of getting a colonoscopy (NOT), researchers have also developed non-invasive screening methods that look for CRC risk factors from stool samples. Some CRC experts also recommend universal genetic screening for Lynch syndrome, which would help identify individuals who need to undergo more frequent screening. Of note, individuals who have a first-degree relative (mom/dad/sister/brother) who were diagnosed with CRC are recommended to start screening at age 40, or 10 years before the age their relative was when diagnosed.

I’m still hyperventilating… Remember, a significant increase in incidence still only reflects a small increase in total numbers of early-onset CRC (12.9 in 100,000). Like for most things, the best thing to do is to live a healthy lifestyle and speak with your primary care provider about any concerns you may have. For future generations, it’s important to support public health practices that keep our youth well-nourished and active.

Microbiome and CRC

Your gut is a breeding ground for bacteria–and we want to keep it that way! We know that a delicate balance of many different types of bacteria is what keeps us healthiest.

Dysbiosis–the term for our gut microbiome being 'out of whack'–has been found to drive colon cancer, with some bacteria being identified as 'good' and others 'bad'. (Really it's much more complex than that though...)

The tie between gut microbiome and colorectal cancer is pretty clear. In one study of mice genetically predisposed to developing intestinal cancer, feeding them a type of bacteria called F. nucleatum significantly increased the number of tumors the mice developed.

These sorts of studies have been done in many mouse models, and are key to advancing our understanding of this complex microbial world living inside us and its role in promoting or protecting us from cancer!

Dr. Talia Henkle has distilled 5 papers saving you 17.5 hours of reading time.

The Science Integrity Check of this 3-min Science Digest was performed by Flávia Oliveira Geraldes

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