How junk food causes cancer - as Morgan Spurlock, maker of Super Size Me, dies from disease aged 53

The link between junk food and cancer was put back into focus today after the death of Super Size Me documentary maker Morgan Spurlock - who died from the disease.

His family said Spurlock, 53, succumbed to 'complications' of cancer but did not reveal which type he had or how long he'd been battling it.

There is no indication his condition was linked to the 2004 movie, which saw him consume nothing but McDonald's meals for a month as a health experiment - even though he suffered a number of health issues in the immediate aftermath.

Piles of research in recent decades have shown that eating lots of processed foods is linked to at least 34 different types of cancers - even in people who are not obese.

Even though the link between ultra-processed foods - including fast food, soda, chips, ice-cream, sugary cereals and deli meats - and cancer is well established, the exact mechanism is still being understood.

One of the ways UPFs may cause cancer is due to their makeup. These foods often contain high levels of saturated fat, added sugars and sodium and are low in nutrients such as vitamins and minerals, and fiber.

If we eat too many ultra-processed foods, we may not eat enough of the foods in the diet that we know boost the immune system and help prevent cancer from forming, such as wholegrains, fruit and vegetables.

Secondly, consuming these foods regularly can lead to weight gain. Being above a healthy weight increases your risk of developing 13 different cancers, including cancers of the bowel, kidney, pancreas, esophagus, endometrium, liver and breast (after menopause).

Excess weight can trigger a host of hormonal changes that can cause tumors to grow. 

A study earlier this year also uncovered a potential missing link between how eating junk food increases the risk of cancer. 

The research out of Singapore found that a compound released when the body breaks down sugary and fatty foods switches off a gene that fights off cancer.

It could, at least in part, explain why cancers among young, ostensibly healthy Americans are becoming so prevalent, particularly tumors in the colon.

The academics looked at the effect of methylglyoxal, a compound released when the body breaks down sugary and fatty foods, on a gene that helps fight off tumors.

They found that methylglyoxal was able to temporarily shut off the BRCA2 gene's ability to protect against cancer forming and growing.

Repeated exposure, such as through eating processed foods, would increase the amount of damage to genes like BRCA2. 

The research adds to a long list of studies suggesting that diet could have an impact on cancer risk, particularly colorectal cancer. 

Research from the Cleveland Clinic, for example, found that people under 50 who ate diets rich in red meat and sugar had lower levels of the compound citrate, which is created when the body converts food into energy and has been shown to inhibit tumor growth.

Red and processed meat also contain compounds such as heme and nitrates, which, when broken down in the body, form compounds that can damage the cells lining the bowel, increasing the likelihood of cancer developing. 

UPFs refers to items which contain ingredients people would not usually add when they were cooking homemade food.

These additions might include chemicals, colorings, sweeteners and preservatives that extend shelf life. 

One example is phthalates - a group of chemicals used to make plastics more durable. 

The chemicals get into food mainly through packaging and food handling equipment such as cellophane and plastic in contact with food. Exposure to phthalates has been linked to breast cancer.

Other research, including the biggest analysis of evidence to date involving 10million people, found that eating a lot of foods such as ready meals, sugary cereals and mass-produced bread is linked to an increased risk of 32 health problems, including cancer.

A 2023 study published in the European Journal of Nutrition found cancer risk shot up when people ate just 350g of ultra-processed food per day over the course of a decade - the equivalent of a large packet of chips or half a sharing bag of Skittles.

This amount was linked to a 20 percent higher risk of head and neck cancer and a 25 percent higher risk of esophageal adenocarcinoma, a type of cancer that grows in the lining of the food pipe.

The study said the disease could result from detrimental changes in gut flora, as well as potential hormonal effects.

Dr David Katz, a specialist in preventive and lifestyle medicine who was not involved in the study, previously told CNN: 'If UPFs contribute to cancer risk, they do it to a small extent by contributing to obesity, and to a much larger extent by other mechanisms.'

'What might those be? Diet-induced inflammation; disruption of the microbiome; adverse epigenetic effects; and many other possibilities come to mind.'