A nutritionist has spoken about the diet he ‘forbids’ his patients to follow - because it is leading to a surge in early cancer cases. Cancer cases in people under 50 have increased in recent decades, and scientists and food experts are saying that eating habits are a big factor in this.

In the UK almost 35,000 people aged between 25 and 49 were diagnosed with cancer in 2019. Incidence rates in this age group grew from 132.9 per 100,000 people in 1995 to 164.6 in 2019 according to Cancer Research UK . The number of people diagnosed with cancer before the age of 50 has been steadily increasing over recent decades, particularly colorectal cancer. Although they only represent 4% of all diagnoses, there are even cases diagnosed between the ages of 15 and 39.

Nutritional epidemiologist Yohannes Melaku said: “We have identified numerous direct links between poor diet and digestive cancers. Unhealthy dietary patterns, marked by high consumption of red and processed meats, fast food, refined grains, alcohol, and sugary drinks, are worryingly linked to an increased risk of gastrointestinal cancer.”

Melaku’s team reviewed research on dietary patterns and gastrointestinal cancer, identifying up to 28 studies. There were some contradictions among studies, but available evidence suggests that healthy dietary patterns tend to reduce cancer risk. Following ths, they analysed data from 97,561 people and found that a diet rich in fibre and unsaturated fats would be associated with a lower risk of colorectal cancer.

“Given that digestive cancers are increasingly common in people under 50 years old, it is time to act to protect the digestive health of the population. Our studies show that nutritional education and promoting healthy eating patterns would be crucial to reducing gastrointestinal cancer risk and improving overall health,” concludes Melaku.

Researchers believe the relationship between diet and cancer would involve processes of low-grade chronic inflammation and harmful interactions through the microbiome. They said foods rich in antioxidants such as berries, leafy greens, fruits, vegetables, almonds, nuts, flaxseeds, turmeric, ginger, garlic, citrus fruits, oily fish, and colourful vegetables are anti-inflammatory.

But Mr Melaku said red meat, sugary drinks, and refined carbohydrates including white bread and other processed foods would be pro-inflammatory foods and have been linked to greater insulin resistance which also increases cancer risk through activation of insulin-like growth factor 1.

Professor Charles Swanton chief clinician for Cancer Research UK said: “Changes to lifestyles and diets over time, and rising obesity, may all contribute to the uptick in early-onset cancer. Genetics, improvements in diagnosis and screening and the microbiome could also play a role.”

Dr Aparna Parikh, a professor of medicine at Harvard medical school and an oncologist at Massachusetts general hospital said: ““This is complex, and the rise in early-onset colorectal cancer cases is driven by various factors, including diet, the environment, and features of the microbiome

"A greater understanding of why cancer cases are rising can help us understand how to intervene and identify high risk patients for cancer screening. By trialling methods to assess risk and prevent early-onset colorectal cancers, we can shape a hopeful and healthier future for younger generations.”

While the causes are multifactorial, two new studies conducted by Flinders University suggest that this drastic increase is largely due to lifestyle changes. In particular, poor diet is highlighted by studies published in the European Journal of Nutrition and Nutrition Reviews.

Gastrointestinal tumours account for one in three cancer deaths worldwide and can occur anywhere in the digestive tract, including the throat, stomach, pancreas, intestines, anus, colon, and rectum. The latter cases are the most diagnosed and lethal.