Convenience Store Food and Early-Onset Colorectal Cancer: Increasing Colorectal Cancer Risk Among Women in Their 20s to 40s - The Small Scars Left by "Convenient Foods" on the Intestines

What Was Revealed After Following 30,000 Nurses for 24 Years

The research team used a prospective study called the "Nurses' Health Study II" in the United States. This famous project has been tracking female nurses in their 40s over the long term, recording detailed changes in their health and lifestyle habits.Harvard Gazette

The following points were clarified in this analysis:

• The subjects were women under 50 who had undergone at least two lower endoscopies (such as colonoscopies), totaling 29,105 individuals.Harvard Gazette

• From 1991 to 2015, detailed dietary questionnaires were conducted every four years to estimate the **intake of ultra-processed foods (in "food" units per day)**.The Washington Post

• On average, participants consumed 5.7 servings of ultra-processed foods per day, accounting for about 35% of their total calorie intake.Harvard Gazette

• Among them, when comparing the group with the lowest intake (average 3 servings/day) and the group with the highest intake (average 10 servings/day), the latter had about a 45% higher risk of developing polyps known as "conventional adenomas" in the colon.The Washington Post

When people hear "polyp," they might think "it's benign, so it's okay," but if left untreated, some can progress to cancer. Andrew Chan, a gastroenterologist at Massachusetts General Hospital involved in the study, notes, "The average risk of a colon polyp turning into cancer over the long term is about 5%," while also pointing out, "Even small ones are not zero risk for malignancy, and the risk increases as they grow larger."The Washington Post

On the other hand, the association with ultra-processed foods was only observed for "conventional adenomas," and no significant association was found with "serrated lesions," which are considered to grow slowly.Harvard Gazette

In other words, this study suggests that there might be a stronger link between "types of polyps that tend to progress to cancer early" and ultra-processed foods.

What Exactly Are "Ultra-Processed Foods"?

The term "Ultra-processed foods (UPFs)" became widely known as a concept through the food classification "NOVA" proposed by Brazilian researchers. Simply put, it refers to industrial foods that heavily use additives and processing techniques unlikely to be used in a home kitchen, accompanied by long ingredient lists and strong marketing.The Washington Post

In this study, the commonly consumed items were:

• Bakery and breakfast products like bread, pastries, and breakfast cereals

• Condiments like dressings, sauces, and mayonnaise

• Sugary and artificially sweetened beverages

This is the lineup.The Washington Post

These foods are

• low in protective components like dietary fiber and polyphenols,

• high in salt, sugar, and saturated fatty acids,

• and contain additives like emulsifiers, sweeteners, and colorings that may affect the gut microbiota,

explains nutritionist Sarah Berry.The Washington Post

However, she also states, "The 'ultra-processed' category is broad, and while some items are clearly unhealthy, others can be beneficial under certain conditions." For example, whole-grain cereals and low-salt, high-protein frozen foods can be nutritionally beneficial depending on how they are used.The Washington Post

The "Causal Relationship" Cannot Be Conclusively Determined Yet

What's important here is that this study is merely an "observational study" and does not prove that ultra-processed foods "directly caused" colorectal polyps. The research team maintains a cautious stance, stating, "While an association was observed, we cannot claim a causal relationship."The Washington Post

There are several reasons for this.

1. Participant Bias
   The subjects were mostly white, highly educated nurses. They also had better access to healthcare than the general population, making it difficult to apply the results directly to other countries or ethnic groups.The Washington Post

2. Self-Reported Dietary Data
   Although the validity of questionnaire-based dietary surveys has been verified, errors such as "I thought I ate" or "I forgot" are unavoidable.Harvard Gazette

3. Polyps ≠ Cancer
   Only a small portion of colorectal polyps actually become cancerous, and there is still a gap between "an increase in polyps" and "an increase in cancer."The Washington Post

Nevertheless, external experts from institutions like Stanford University have evaluated the study, stating, "There is still little research on early-onset cancer, and large-scale data like this is valuable."The Washington Post

The Reality of Increasing "Early-Onset Colorectal Cancer" Worldwide

Why has this study garnered so much attention? The background lies in the reality that colorectal cancer among those under 50 (early-onset colorectal cancer) is continuously increasing worldwide.

• In the United States, the proportion of colorectal cancer patients under 50 has increased from 6% in 1990 to 13% in 2023. Currently, 1 in 5 is diagnosed under the age of 55, according to reports.GI Oncology Now

• International analyses show that about 10% of new colorectal cancer cases worldwide occur in individuals under 50, with increasing incidence rates among younger age groups in 27 countries.Cancer Information Center

• In high-income countries, including Japan, colorectal cancer in those in their 60s and 70s is actually on the decline, while patients in their 20s to 40s are increasing, as shown in multiple studies.The Lancet

Changes in lifestyle habits, lack of exercise, obesity, alcohol consumption, smoking, gut microbiota, and environmental pollutants are among the many suspected factors. Recently, a study gained attention for finding that the tumor DNA of colorectal cancer patients had characteristic scars from a toxin called "colibactin" produced by certain E. coli.Reuters

Ultra-processed foods are just "one piece" of that enormous puzzle. However, this study suggests that "the piece might be larger than we thought."

It Is Not Unrelated to Us in Japan

So, to what extent does this concern those of us living in Japan?

Japan has long been described as a "country of rice, fish, and vegetables," but in reality, dietary habits have changed significantly over the past few decades. Studies using national surveys have shown that as the intake of ultra-processed foods increases among Japanese people, the overall quality of their diet definitely declines.##HTML_TAG_