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Here’s another reason to eat fresh food: a new study shows that people who eat more highly processed foods such as chicken nuggets and instant noodles have a higher risk of cancer.

It’s long been known that eating fresh fruits and vegetables and whole grains lowers the risk of cancer. Obesity also raises the risk of cancer, and junk food is full of calories.

But this study, conducted by a team in France and Brazil, suggests that ultra-processed foods carry an extra risk of cancer, above and beyond being nutritionally bad for you.

“Ultra-processed food intake was associated with higher overall cancer risk,” the team wrote in their report, published in the British Medical Journal’s online publication The BMJ.

“A 10 percent increase in the proportion of ultra-processed foods in the diet was associated with a significant increase of greater than 10 percent in risks of overall and breast cancer,” they added.

By ultra-processed they mean very, very processed.

The foods associated with extra cancer risk include:

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mass produced packaged breads and baked goods

sodas and sweetened drinks

instant noodles and soups

sweet or savory packaged snacks

industrialized confectionery and desserts

meat balls, chicken and fish nuggets

other reconstituted meat products transformed with addition of preservatives other than salt (for example, nitrites)

frozen or shelf-stable ready meals

Other food products made mostly or entirely from sugar, oils and fats

Less-processed foods such as cheese, pasta and canned vegetables did not raise cancer risks, Bernard Srour of the French national research organization Inserm and colleagues found.

The group used an ongoing survey of more than 100,000 French adults who regularly fill out questionnaires about their lives, including details on 3,300 different food items.

After five years, more than 2,200 cases of cancer were diagnosed in the group.

Other bad habits

The researchers stress that the study does not show that the highly processed foods caused the cancers. People who eat a lot of junk food have other habits that predispose them to cancer, not the least of which is smoking.

We are a long way from understanding the full implications of food processing for health and wellbeing

But they took into account many of these, including smoking but also age, sex, educational level, family history of cancer, and physical activity — and they still found the link between eating junk food and cancer.

There are several ways that processed foods could in theory raise cancer risks, they noted.

“Firstly, ultra-processed foods often have a higher content of total fat, saturated fat, and added sugar and salt, along with a lower fiber and vitamin density,” they said.

Processing also creates carcinogenic compounds, such as acrylamide and polycyclic aromatic hydrocarbons. And these foods are packaged, and chemicals can leach out of the packaging.

“Finally, ultra-processed foods contain authorized, but controversial, food additives such as sodium nitrite in processed meat or titanium dioxide (TiO2 , white food pigment), for which carcinogenicity has been suggested in animal or cellular models,” they added.

Other researchers pointed out that ultra-processed foods is both a broad and vague category.

“Results from this study support the claim that the shift in the world’s food supply to highly processed foods may partly account for increasing trends in the incidence of non-communicable diseases, including cancer,” Martin Lajous and Adriana Monge of the National Institute of Public Health in Mexico wrote in a commentary.

“We are a long way from understanding the full implications of food processing for health and well-being,” they added.

Other experts said the advice for preventing cancer remains the same: