Bowel cancer is expected to infect many more young people in the next 20 years, partially due to junk food intake and inactivity, the Daily Mail reported on Friday.

Cases in patients over 50 have declined, but numbers of adults between the ages of 20 and 49 are expected to jump. Studies conducted between 1975 to 2010 show that cases among the elderly have fallen, partially because they are screened more often.

Patients between 20 and 49 have seen a 1.99 percent increase, which has been most pronounced in people under 34. The rate of bowel cancer in people between 20 and 34 is expected to soar by roughly 37 percent by 2020. By 2030, this incidence rate is expected to be at a 90 percent increase.

There is good news, however, for patients over 50: incidence rates of bowel cancer will decrease by roughly 23 percent by 2020 and 41 percent by 2030.

"The increasing incidence of colorectal cancer among young adults is concerning and highlights the need to investigate potential causes and external influences such as lack of screening and behavioral factors," said Christina Bailey of the University of Texas.

Carbonated drinks, as well as chocolate, cookies and crackers could increase a patient's chances of getting the disease, according to previous research.

Bowel cancer is also linked to the consumption of processed and red meats, including sausages. 

University of Texas Anderson Cancer Center researchers studied data from the Surveillance, Epidemiology and End Results database to look at age discrepancies in bowel cancer cases, according to Medical News Daily. The overall rate of the disease had decreased by .92 percent between 1975 and 2010 - roughly 1 percent in men and .91 percent in women. 

The main symptoms of disease are changes in bowel habits - such as frequent and looser stools - abdominal pain and blood in the stools.