A study of nearly half a million people revealed that eating certain types of food is linked to cancer - but there's a simple fix

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A fiber-rich diet that includes fresh produce, legumes, and nuts was linked to lower cancer rates.

• A new study of 471,495 European adults found that people who eat bigger portions and consume more meat, junk food, and alcohol have higher rates of cancer.
• Conversely, people whose diets are filled with vegetables, legumes, fresh fruits, fish, and lean meats were less likely to develop cancer.
• A French nutrition rating system that's already in use could help people maintain a healthier diet and consequently reduce cancer risk.

The old advice about letting food be your medicine is ringing truer than ever in the face of some new research.

A study published Tuesday in the journal PLOS Medicine suggests that what you eat can either raise or reduce your risk of deadly cancers.

The study's 56 authors surveyed the diets of 471,495 people in 10 European countries, over an average time period of 15 years.

Their findings revealed that European people with less nutrient-rich diets - which included more processed meats, salt, sugary pastries, and saturated fats - were more likely to develop cancer than people who ate food with more nutrients and dietary fiber.

"In this study we observed a higher risk of cancer for people eating, on average, more foods with a high content in energy, sugar, saturated fat or sodium" lead study author Mélanie Deschasaux told Business Insider in an email. "For example, processed meat, pastries, cola."

People whose diets were lowest in nutritional quality (the bottom 20% of the group studied) were 7% more likely to develop cancer compared to people with the most nutritious diets (the top 20%). But Deschasaux said that number is less significant than the clear, consistent, and compelling trend the researchers found: a diet plentiful in plant-based proteins like beans and nuts, along with fiber-rich fruits and vegetables, seems to be the best for a cancer-free life.

The researchers found this was especially true for certain kinds of cancer, including colon, stomach, lip, tongue, mouth, sinuses, stomach, lung (for men), and liver and breast (for women).

A growing body of evidence supports one type of diet for longevity

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The authors of the new study controlled for other factors, including a person's family history of cancer, how active they were, their body mass index, and whether they smoked. Regardless of any of those variables, they found, a person with a low-quality diet was more likely to develop cancer.

Interestingly, some of the countries with the worst cancer outcomes included France, the UK, and Germany. People were generally healthier in Mediterranean countries like Greece, Italy, and Spain (though health outcomes were also good in Norway and among vegetarians in the UK).

The results are the latest in a growing body of evidence that suggests focusing on plant-based, fiber-rich diets can lead to a long life, but consuming processed food can be harmful. Studies consistently find that following a Mediterranean diet - which is high in fruits, vegetables, healthy fats like olive oil and avocado, and plenty of fiber from beans and nuts - is associated with living a longer, healthier life.

In February, another study of more than 100,000 French adults revealed that those who ate more processed and packaged foods like chips, sugary cereals, frozen microwave dinners, and sweet drinks were more likely to develop all kinds of cancers.

Although it's a bummer that tasty processed foods can hurt you, the good news is that the reverse is equally true: eating more whole grains and fiber-rich veggies can decrease your risk of developing cancer. That's especially true when it comes to colon cancer, which is becoming one of the most common cancers plaguing young adults in their 20s.

The reason dietary fiber can help prevent cancer is that it cannot be absorbed by the body, and instead improves the way we digest food, "shortening the amount of time that wastes travel through the colon," according to the Physicians Committee for Responsible Medicine.

The committee adds that "when bacteria in the lower intestine break down fiber, a substance called butyrate is produced which may inhibit the growth of tumors of the colon and rectum."

Fiber from whole grains specifically is good for your gut because the bran and germ from a grain can stimulate antioxidant activity and also includes key nutrients like vitamin E, copper, and zinc.

A scoring system for food

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Sometimes it feels like healthy eating would be much easier with a cheat sheet. Fortunately, the researchers behind this new study say France has created a good one.

The grading system, called "Nutri-Score," is a way to evaluate packaged foods based on their ingredients. Items score points for having more fiber, protein, fruit, and vegetables, but they lose points if they're loaded with sugar, salt, saturated fat, or lots of calories. Essentially, the ranking follows the dietary rules that the new study found can play a role in cancer risk.

Based on a food's final total, it gets a letter grade and a color. A food with a dark green "A" is healthiest, while a dark orange "E" is the worst.

Santé publique France

This Nutri-Score system was implemented in France last year. But it's not mandatory.

The tool was rolled out on a voluntary basis in France last year - food manufacturers can choose whether or not to include it on their products.

But as of October, 2017, only six French food manufacturers were using the score on the front of their packaging, according to FoodNavigator.com. Those companies include yogurt giant Danone and french-fry maker McCain.

The study authors say their results suggest the Nutri-Score scale is scientifically sound and useful.

"A healthy diet is not just about cutting out one particular food or adding another, it is about balance," Deschasaux said.

If people were given simpler nutrition information like these letter grades, it'd be easier to make better eating choices and reduce our cancer risk. But this new study indicates that the foods that would garner the best scores are plants like legumes and vegetables. And those items don't require any plastic wrap or box displaying a special score.