Can processed foods be part of a healthy diet?

From frozen meals to luncheon meats to cereals to soda pop, processed foods are a part of most people’s diet. They’re convenient and taste good. And as our lives have gotten busier, it becomes harder to resist the Siren call of processed foods. But can processed foods be part of a healthy diet?

For years, I would pack a ready-made frozen burrito in my lunch. It was easy and I liked the taste, even though I knew the burrito was made in some far-off factory with ingredients that stretched around the plastic wrap, many of which I can’t even pronounce. And it probably wasn’t a key part of a healthy diet. But I’m not alone. These types of ultra-processed foods can account for more than half of a person’s daily calories. A number that has increased over the years.

What are processed foods?

Any food that has been altered in some way before eating is considered processed. This can be as simple as cooking, freezing or canning. But it can be far more complex, such as foods with multiple ingredients and with added salt, sugar or other substances. Foods are generally processed to extend shelf-life (prevent them from going bad), make food production easier and cheaper, and to make it more convenient to transport.

A commonly used method to categorize process foods is the NOVA classification system. In this system, foods are classified into four categories, with whole foods and minimally processed foods in Group 1 to ultra-processed foods in Group 4. In between those two groups are things such as cooking oil, milk, cheese, bread and canned fruits and vegetables, foods that may be considered staples in most diets.

What about ultra-processed foods?

Ultra-processed foods are foods that have little resemblance to the foods they’re made from. Think of ready-to-eat meals, cereals and soda pop. These foods will have additives to make them last longer. This makes them more convenient to store at home and cook. They’re also cheaper and more energy dense than their unprocessed counterparts.

It’s pretty easy to recognize ultra-processed foods. They’re pre-packaged and most don’t have a best before date. And the more layers of packaging a food has, the more processed it likely is. In general, processed foods are found in the aisles of grocery stores. Foods that are fresh tend to be around the perimeter as it’s easier to re-stock them. However, that isn’t always the case. You’ll also find ultra-processed meats such as sausages and bacon in the cold section near the butcher.

Processed foods are designed to be addictive and keep us eating more. In a study where people were given free access to meals from processed foods, they ate more and gained more weight compared to when they were given unprocessed foods. In just after two weeks of processed foods, hormones involved in hunger increased suggesting these foods may make it harder to feel full.

The Concern of Ultra-processed Foods

Lacking in nutrition, these foods may be doing us more harm than we think. Ultra-processed foods have been linked to increased chances of getting cancer and heart disease, as well as early death. Eating four servings of ultra-processed foods a day was associated with a 62% greater chance of death in young adults compared to eating less than two per day. And a comprehensive review of various studies confirmed these findings and demonstrated associations of ultra-processed foods with mental illness, lung and gut disorders.

It’s not quite clear how these foods are affecting us. One possibility is that eating ultra-processed foods replaces otherwise healthy foods. You might not think to eat as many vegetables after you’ve had that frozen pizza for dinner. But it’s also likely more than this. Processed foods may actually alter our metabolism that leads to poor health.

The additives in ultra-processed foods may be bad for the bacteria in our gut (our microbiome). Bacteria in your gut have recently been linked to your health. Eating more ultra-processed foods is associated with less types of bacteria in the gut. This may be due to the high levels of sugar and lack of fibre in processed foods, which can lead to more of the bad types of bacteria and less of the good types.

It’s also possible some of the additives in processed foods, as well as elements absorbed into the food from its packaging, are carcinogenic. While in small amounts these additives are believed to be safe and have been approved by government regulatory bodies, the long-term effects of eating processed foods with these additives is unknown.

Not All Processed Foods are Bad

But it would be wrong to lump all processed foods together. According to the Nova classification system, stored-bought bread is in the same category as bright-coloured cereal with all its additives. Yet these two foods have quite different ingredients, which likely have different effects on one’s health. While the Nova classification system has been helpful to use in large research studies to highlight the potentially harmful effects of ultra-processed foods, it uses broad definitions which are considered hard to define.

And some processed foods may actually be healthier, or at least not worse, choices over unprocessed foods. Frozen fruits and vegetables, once thought to be inferior to fresh, are commonly frozen at the source during peak harvest. In contrast, fresh foods are often harvested earlier to allow them to ripen while in transit. When compared to fruits and vegetables stored in a refrigerator for ten days, those frozen for three months had similar or higher values in vitamins.

While it may be hard to totally avoid processed foods in your diet, and you may not need to, minimizing how much you eat of highly processed foods is a good step to healthy eating and healthy living. And it’s probably no coincidence that one of the common things about the longest living populations in the world is they avoid these foods too.

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This post was originally published on Jun 12, 2019 and updated on March 13, 2024.

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