Early-onset of colon cancer is rising in young adults: 5 things to know

When you think of colorectal cancer — more commonly known as colon cancer — you likely imagine someone over 50. But increasingly, younger people — in their 20s, 30s, and 40s — are being diagnosed with what’s called early-onset colorectal cancer (EO-CRC).

Colon cancer is a type of cancer that develops in the tissues of the colon or rectum. It starts in the large intestine (colon) and often develops from small, noncancerous clumps of cells called polyps. It's one of the most common types of cancer worldwide and the second leading cause of cancer death in the United States.

Early-onset colorectal cancer (EO-CRC) is defined as colorectal cancer diagnosed before age 50. Thanks to obesity and alcohol consumption, bowel cancer has become the primary cause of the rising death toll among young adults. It is getting increasingly common, especially among younger adults.

And therefore, experts are sounding the alarm: between changing lifestyles, delayed diagnoses, and a lack of awareness, the trend is getting more worrisome by the day. This begs a crucial question: what is happening, and what can be done about it?

Here, we unpack five key things to know about this shift — from rising rates and risk factors to symptoms, screening, and how you can reduce your risk. The bottom line: even though the chance is still lower for younger adults than older ones, the risk is climbing — and early detection is more important than ever.

Data show that EO-CRC (typically defined as colorectal cancer diagnosed before age 50) is increasing while rates among older adults are falling. A major study found that from 2001 onwards, incidence in younger adults rose by about 2.1% per year, with rectal cancers climbing faster (approximately 3.9% per year) compared to colon cancers.

Furthermore, the International Agency for Research on Cancer (IARC) noted that, in several countries, the rate of EO-CRC may double roughly every 15 years if the current trend continues. In short, if you’re younger than 50, you’re not ‘safe’ from colorectal cancer — the odds are increasing.

It’s not just the traditional risks (age, family history) at play for the young lot falling prey to EO-CRC. For early-onset cases, distinctive patterns are emerging.

On one hand, genetic or hereditary syndromes (e.g., Lynch syndrome or familial adenomatous polyposis) account for about 20-30% of EO-CRC, but that leaves more than half of cases with no known inherited cause. On the other, lifestyle and environmental factors matter a great deal. Poor diet (high in processed and ultra-processed foods), low fiber, obesity, sedentary behavior, gut-microbiome changes, and even early-life antibiotic use are being implicated as possible risk factors for the development of EO-CRC.

This implies that younger adults should pay attention to these risk signals, even without a family history.

One of the big problems with EO-CRC is, young people and their healthcare providers may not even suspect cancer for their age bracket, leading to symptoms getting dismissed or misdiagnosed. According to the Colorectal Cancer Alliance, over 70% of young-onset patients were diagnosed at advanced stages (stage III or IV) — much higher than older groups.

What’s more? Young adults with colorectal cancer tend to have more aggressive or advanced disease at diagnosis. For instance, younger patients are more likely to present with rectal bleeding, changes in bowel habits, abdominal pain, or unexplained weight loss. Delays in recognizing these symptoms may contribute to later-stage diagnosis.

Because screening has traditionally focused on older adults, younger individuals may not be tested promptly, which can lead to missed opportunities for early detection. But the bottom line remains the same: don’t ignore symptoms like rectal bleeding or persistent bowel changes just because you’re “too young”.

Because younger individuals are increasingly at risk, awareness of symptoms and timely action are keys to better treatment and management. Young people — even in their 20s and 30s — must pay attention to warning signs such as blood in the stool, persistent abdominal pain, changes in bowel habits, or unexplained weight loss. Medical guidelines have already started to shift: bodies like the American Cancer Society and the US Preventive Services Task Force now recommend initiating average-risk screening at age 45 rather than 50 in many jurisdictions. So if you have a family history of colorectal cancer or a known genetic syndrome, screening may begin even earlier. Discuss with your healthcare provider whether early testing is appropriate for you. More importantly, younger people should be encouraged to speak up if they have symptoms — don’t assume “you’re too young” to worry about colorectal cancer.

While some risk factors (like genetic predisposition) can’t be changed, there are several evidence-based lifestyle steps younger adults can take to lower their colorectal cancer risk:

A healthy diet: Opt for a diet rich in whole grains, fruits, and vegetables, and high in fiber, while limiting processed meats and sugary drinks.

Stay active and maintain a healthy weight: Excess body mass index (BMI) has been tied to increased colorectal cancer risk in younger age groups. So, regular physical activity is a must, whereas sitting for long periods is linked to a higher risk.

Limit certain habits: In case you’re a drinker and smoker, check your alcohol consumption and quit smoking — both are well-known risk factors, especially for colon cancer.

Discuss with your doctor: this is one of the most important points to keep in mind — if you have symptoms of colorectal cancer or a family history, ask whether earlier screening or specialist consultation is needed. In case they are, delaying diagnosis will only make things worse.