New research may have discovered an unexpected driver behind the mysterious rise of colon cancer cases in young people.
The study found patients with high blood-sugar levels were up to 65 percent more likely to be diagnosed with the cancer before age 50 than their peers.
Diabetics were at the highest risk, but those with prediabetes - where blood-sugar levels are higher than normal but not high enough to be classified as diabetes - were also at an elevated risk.
Experts who analyzed more than 500,000 people's medical records as part of the study are now calling for 'tighter glucose control' to be a priority for young people.
It is thought that having high blood sugar may partly raise the risk of cancer because cancer cells use excess glucose as fuel. The findings could be significant, given around 100million Americans and 5million people in the UK have prediabetes.
The above graph shows the rise of colorectal cancer in Americans under 50 over the last two decades
Data from JAMA Surgery showed colon cancer is expected to rise by 90 percent in people ages 20 to 34 by 2030
The US has the sixth highest rate of early-onset cancers - 87 cases per 100,000 people - and colon cancer is among the fastest rising.
Diagnoses among people under 50 years old, which are classified as early-onset, are expected to rise by 90 percent in people 20 to 34 years old from 2010 to 2030.
Experts have sought to blame everything from ultra-processed ingredients to a change in the body's microbiome - collection of beneficial bacteria in the gut.
But now, scientists may have found a link between blood sugar and colon cancers.
Blood-sugar levels are the amount of glucose in your blood. Glucose is a type of sugar that comes from food and is the body's primary source of energy.
A normal blood glucose range is 70 to 99 milligrams per deciliter (mg/dL).
Levels between 100 and 125 mg/dL are considered prediabetic and anything 126 mg/dL or higher classifies a person as a type 2 diabetic.
However, a person can have higher-than-normal levels of glucose, a condition called hyperglycemia, without having diabetes.
Some causes can include a diet high in carbs and sugar, lack of physical activity, obesity, physical trauma, infections, stress, certain medications and other medical conditions such as pancreatic diseases, Cushing's syndrome and polycystic ovary syndrome.
Symptoms of hyperglycemia include extreme thirst, frequent urination, recurrent infections, weight loss and blurred vision.
The new study was conducted by a group of researchers from Beijing, the Chinese Academy of Science and Peking Union Medical College.
It looked at the medical records of two cohorts of adults - one group from the UK and one in China.
Researchers found, overall, a higher blood glucose level was associated with an increased risk of developing early colorectal cancer.
Levels higher than 126 mg/dL were associated with a 61 percent increased risk of early-onset CRC compared to people with levels below 126 mg/dL among the UK cohort.
Among the Chinese cohort, glucose levels higher than 126 mg/dL were associated with a 65 percent increased risk of early-onset colorectal cancers.
The above shows the symptoms and their frequency in early onset patients, those who develop colon cancer before the age of 50, and late onset patients, those who develop the cancer after 50
The researchers, whose study was published in the Journal of the National Cancer Center, said their results suggest 'tighter glucose control should be a priority for younger age groups.'
There were several reasons the researchers gave for the connection between blood sugar and colorectal cancers.
First, high glucose can directly damage DNA and promote the proliferation of damaged cells.
It can also facilitate the migration and invasion of cancer cells throughout the body.
Second, cancer cells utilize glucose, so increased levels in the body provide the cells with more energy.
High blood sugar also interrupts certain signaling in the body that can stimulate the growth and movement of cancer cells.
Finally, the study stated, elevated glucose levels have been associated with chronic stress and inflammation within the body, which are potential contributors to cancer.
The researchers wrote the surge in early-onset colon cancers represents a 'significant cancer burden among young adults... [and] the drivers of this disturbing trend are not well understood.'
The ream wrote: '... our findings underscore the need for greater public health efforts targeting obesity, metabolic dysfunction, and hyperglycemia as part of a multi-pronged approach to mitigate the growing burden of CRC, especially across younger age groups.'
Experts aren't sure exactly what is causing the rise in early-onset cancers, but posit it could be from a meat-heavy and high-fat diet, the rise of obesity or exposure to ultra-processed foods, artificial ingredients and additives, as well as harmful chemicals.
One factor that has previously been considered behind the rise was prior antibiotic use. However, a new, separate study in the journal Clinical Gastroenterology and Hepatology, found the few studies to examine this link have reported conflicting results.
California researchers looked at the medical records of 4.5million patients in the state's Kaiser Permanente healthcare system and analyzed the records of 18- to 49-year-olds who had been diagnosed with early-onset colon cancer between 1998 and 2020 with a history of taking oral antibiotics.
Results showed a relationship between prior antibiotic use in adulthood and early-onset CRC was not statistically significant.
Separate research from the University of Missouri-Kansas City looked at rates of colorectal cancer in people 10 to 44 years old over the last two decades and found cases had risen in all age groups.
The rate of colorectal cancers grew 500 percent among children ages 10 to 14 and 333 percent among teenagers 15 to 19 years old.
Rates rose by 71 percent among people 30 to 34 to seven cases per 100,000 people. And among people 35 to 39, rates rose by 58 percent to 12 cases per 100,000 people.
According to the ACS, 37 percent of colorectal cancers are in people younger than 50 years old, compared to 24 percent of those in people 65 or older.
And CRCs have increased two percent in people younger than 55 since the mid-1990s and deaths have increased one percent since the mid-2000s.
The five-year survival rate for CRCs is 64 percent, but that drops to 14 percent if the cancer has spread, which commonly occurs in early-onset cases because symptoms are often not present or are misdiagnosed until the cancer has spread throughout the body.
Symptoms include changes in bathroom habits, blood in stool, weakness, fatigue, nausea, loss of appetite, a lump in the abdomen or rectum, diarrhea, abdominal cramping, constipation and vomiting.