Why soda may increase the risk of early-age colon cancer

Chadwick Boseman's death from colon cancer at the shockingly young age of 43 was a wake up call. Colon cancer, like most cancers, is more common in older people, and early detection has been focused on the over-50 population. Rates of colon cancer have indeed been declining in the older population – the development of cancer in the gut can be prevented when polyps are removed during colonoscopy before they have a chance to turn into a cancerous tumor – but the rates have risen sharply in younger adults. For people born in the 1990s the risk of colon cancer is twice that of people born in the 1950s.

What explains the rise in cancer among Millennials and Gen Xers? 

The most likely explanation is lifestyle risk factors: Colon cancer risk factors include poor diet, obesity, smoking, alcohol consumption and lack of exercise. In other words, as fast food, obesity and unhealthy sedentary practices rise, so would the risk of colon cancer.

A new study in the journal Gut looks at the leading source of added sugar in the US diet – sugary drinks – and the risk of early-age colon cancer. The researchers analyzed data from almost 120,000 women who were part of the Nurses’ Health Study II between the years 1991-2015, with a 24 year follow up, looking at diet and health outcomes. 

Among this large group there were 109 cases of early-age (before the age of 50 years) colon cancer.

Women who drank more sugary drinks were more likely to be less physically active and have lower diet quality – eat less fruits, vegetables and fiber, and eat more processed meat. But even after adjusting for all the above colon-cancer risk factors, as well as for obesity, alcohol intake etc., higher sugary drink intake was associated with an increased risk of early colon cancer.

Women who drank more than 2 servings of sugary drinks had more than double the risk of developing early onset colon cancer, with a dose-response additional risk with each additional sugary drink. The increased risk was associated with sugary drinks, and not with fruit juices.

Added sugar and your gut

Americans’ consumption of sugary drinks rose dramatically in the second half of the 20th century, with kids drinking soda earlier in life and in greater quantities. 

We already know that sugary drinks are linked with obesity, as well as with several chronic diseases such as type 2 diabetes and heart disease.

This study shows a link between sugary drinks and early-age colon cancer in a large women cohort. What could explain that? We already know that sugary drinks promote weight gain by the sheer fact that they introduce plenty of calories, yet lead to very little satiety, and therefore can result in overeating and weight gain. They can also make blood sugar rise quickly, leading to a rise in insulin, which can long-term result in insulin-resistance, inflammation, type-2 diabetes and weight gain. All of these are known risk factors for colon cancer.

But beyond that, the authors write:

“By causing dysbiosis and endotoxaemia, fructose can impair gut barrier function and increase gut permeability, which could promote colorectal carcinogenesis. A recent experimental study demonstrated that HFCS-treated mice had substantial colon tumour growth with aggressive tumour grade, independent of obesity and metabolic syndrome,30 which lends additional support to the link between SSBs (sugar sweetened beverages) and CRC (colorectal cancer) risk.”

Allow me to explain. Fructose is part of most of the added sugars we consume, including table sugar and high fructose corn syrup. Fructose in sugary drinks overwhelms the small intestine’s absorption capacity and reaches the large intestine where it can cause imbalance in the microorganisms living within the gut (the microbiome), and lead to the production of bacterial toxic materials, resulting in further changes in the gut that promote the formation of cancer cells.

Colon cancer rates are rising among young people, but fortunately this disease is still relatively rare. 

The other afflictions associated with the soda habit are much more common, and much more evidence connects the sugary-drink habit with outcomes such as hypertension, type 2 diabetes and heart disease.

Dr. Ayala