Scientists are warning people to look out for four key symptoms of a deadly disease as cases have been rising among young people. According to experts, you should see your doctor as soon as possible if you spot any of these signs - even if you are young and seemingly healthy.

Researchers from the US pinpointed the most important symptoms of bowel cancer - which is also known as colorectal cancer - to be aware of, some of which can appear two years before a diagnosis.

Having just one of the symptoms doubles the risk of bowel cancer, they claimed, while three or more can multiply the likelihood by 6.5 times.

As reported by The Mirror, a team at Washington University School of Medicine in Missouri, studied data on more than 5,000 patients with early-onset bowel cancer. 

They found that four key signs usually show between three months and two years before being diagnosed. These were:

• Abdominal pain
• Rectal bleeding
• Diarrhoea
• Iron deficiency anaemia

Doctors said each indicated an increased risk in patients under age 50.

It comes as experts issue a warning to young adults that bowel cancer "is not simply a disease affecting older people". 

Researcher and associate professor Yin Cao explained: "Colorectal cancer is not simply a disease affecting older people; we want younger adults to be aware of and act on these potentially very telling signs and symptoms - particularly because people under 50 are considered to be at low risk, and they don’t receive routine colorectal cancer screening.

"It’s also crucial to spread awareness among primary care doctors, gastroenterologists and emergency medicine doctors. To date, many early-onset colorectal cancers are detected in emergency rooms, and there often are significant diagnostic delays with this cancer." 

Dr Cao said two symptoms in particular - rectal bleeding and iron deficiency anaemia, a blood condition causing tiredness and pale skin - mean patients should immediately see their doctor and ask for an endoscopy.

According to the scientists, people born in 1990 have double the risk of colon cancer and four times the risk of rectal cancer compared with young adults born in 1950.

"Since the majority of early-onset colorectal cancer cases have been and will continue to be diagnosed after symptom presentation, it is crucial to recognize these red-flag signs and symptoms promptly and conduct a diagnostic work-up as soon as possible," Dr Cao added. 

"By doing so, we can diagnose the disease earlier, which in turn can reduce the need for more aggressive treatment and improve patients’ quality of life and survival rates."

The NHS lists symptoms of bowel cancer as:

• Changes in your poo, such as having softer poo, diarrhoea or constipation that is not usual for you
• Needing to poo more or less often than usual for you
• Blood in your poo, which may look red or black
• Bleeding from your bottom
• Often feeling like you need to poo, even if you've just been to the toilet
• Tummy pain
• A lump in your tummy
• Bloating
• Losing weight without trying
• Feeling very tired for no reason
• Anaemia, which can make you feel very tired, short of breath and have headaches.

Data from Cancer Research UK shows that bowel cancer is the fourth most common cancer in the UK, accounting for 11 percent of all new cancer cases. However, it is the second most common cause of cancer death with around 16,800 fatalities every year.