Ask an RD: What is processed food and just how bad is it?

Some foods are more processed than others. A registered dietitian explains what you need to know about ultra-processed foods and how they might be harmful to your health.
Image: Grilling hot dogs
Highly processed foods make up a big part of our diets — up to 60 percent of the calories we consume by some accounts. Matt Carey / Getty Images
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By Samantha Cassetty, RD

Much of the food we eat today has been processed in some fashion. Technically speaking, the bag of pre-washed spinach greens that has permanent residency in my fridge is a processed food. Making life in the kitchen less stressful — not to mention healthy eating much easier — is the gift of modern food processing, but the system isn’t made up entirely of bagged lettuce and frozen fruit (another form of processing). Let’s take a closer look at processed food and how it might be harmful to your health.

What counts as processed food?

Anything that takes a trip through a manufacturing plant is technically a processed food. Food may be processed for a number of reasons: to prevent spoilage (allowing you to keep items in your fridge or pantry longer); to make it more convenient (pre-washed salad greens, canned beans, and frozen fruits and veggies are prime examples); to improve flavor or texture by using certain additives; and to boost vitamin or mineral content (such the nutrients added to enriched, refined grains). Food might also be processed to keep it safer, say, by killing potentially harmful pathogens. For example, nitrates are added to certain cured meats and poultry to inhibit Clostritium botulinum, a life-threatening bacteria.

While I certainly appreciate the advantages of processing food — less kitchen stress and a reduced risk of deadly bacteria are appealing! — there are downsides to processing as well.

What’s an ultra-processed food?

There are degrees of processing and while there’s no standard definition, essentially, an ultra-processed food is farther removed from its natural state. One classification system — NOVA, developed at the University of Sao Paulo in Brazil — defines processed foods as modified whole foods with just two or three ingredients, which are usually used to make whole foods last longer or taste better. Examples of processed foods might be canned tuna (perhaps processed with salt and oil) or cheese.

By comparison, they suggest that ultra-processed foods are formulations that are made with sugars, oils, fats, or salt, and that have little, if any, intact whole foods. These foods take a longer trip down the manufacturing process and may contain ingredients designed to make them more convenient or especially tasty.

This classification system may be a useful research tool, and may even be helpful in guiding your own decisions, but it’s still a bit of a loose categorization in my opinion. For example, they group white pasta — which lacks intact grains and includes added nutrients to make up for what was lost during processing — as minimally processed; I’d place it squarely in the more processed camp. (I took an informal poll among some RD friends who agreed with this assessment.)

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Even whole foods can be processed to varying degrees, and oats are a fine example of this. On one end, you have steel cut oats, which take a longer time to cook because they’ve been less processed; at the other end, you have instant oatmeal, which has been steamed and rolled to make it cook more quickly. Further processing of oatmeal might involve adding sugars and then additional processing might include flavor additives.

According to researchers, a better way to assess how processed your food is might be to inspect the ingredient list for added sugars and industrial ingredients that you wouldn’t find in your kitchen. Examples of these ingredients include (but aren’t limited to) soy protein isolate, high fructose corn syrup, fruit juice concentrate, gluten, maltodextrin, inulin, and gums. These ingredients should tip you off to the fact that the product has taken a pretty long trip through a manufacturing process and have entered the highly processed zone.

Why is processed food less healthful?

Though there’s no unified agreement over what foods fall in the heavily processed camp, there is widespread agreement that eating more whole foods is good advice. Evidence is steadily streaming in that processed foods are linked with weight problems and poorer health. That may be because these foods are often packed with sodium and/or sugar, which are linked to health troubles on their own. Or it may be that heavily processed foods contain additives, pro-inflammatory oils, or refined grains, all of which can be problematic. To be fair, much of the research we have doesn’t prove cause and effect — just that there’s a link, though it makes logical and perhaps even biological sense. We’re just not sure what biological mechanisms are at play.

A new study offers some proof — in this case, that these heavily processed foods might cause you to gain weight. 20 volunteers were placed on a heavily processed or a minimally processed diet for two weeks (volunteers participated in both diets in random order). The meals they ate were closely matched for calories, fiber, sugar, fat, carbs, and protein with the difference being the types of foods that were offered at mealtimes. A heavily processed breakfast might be a bagel and cream cheese; a less processed one might be unsweetened oatmeal, fruit, and nuts. Though the meals were matched for nutrients, participants could eat as much (or little) as they liked.

In the end, they gained weight when eating ultra-processed foods and they lost it when eating less processed foods. And remember, these were the same people! They tended to eat faster when consuming more processed meals and ultimately ate an average of 500 calories more per day eating those foods, gaining an average of two pounds during the short study period.

What’s troubling is that highly processed foods make up a big part of our diets — up to 60 percent of the calories we consume by some accounts. Not surprisingly, foods that fall in the ultra-processed camp also contribute nearly 90 percent of added sugars to our diets. These foods are low in nutritional quality and have been linked with a higher rate of obesity, type 2 diabetes, heart disease, certain forms of cancer, and GI diseases — basically, a vast spectrum of health concerns. They’ve also been linked with unfavorable shifts in your gut microbiome that might promote inflammatory diseases.

What can I eat?

Remember that processing is a spectrum so cutting way back on heavily processed foods doesn’t mean you have to give up convenience or packaged foods. You can still rely on conveniently packaged whole or very minimally processed foods, like quinoa, canned beans, nuts, nut butters, and fruits and vegetables (such as frozen, dried, or unseasoned canned versions).

And recall that what experts do agree on is that basing your diet on more whole foods (and especially plant-based ones) and limiting added sugars, excess sodium, and heavily processed grains and snack foods is a healthful habit. Here are some pointers to help you on that front:

  • Replace processed deli meats (even chicken and turkey) with leftover dinner meats or fresh meats (like a store-bought rotisserie chicken or store-bought fresh roasted turkey).
  • Consider snacking on fresh or lightly processed foods over chips and other typical fare. Examples include nuts and seeds, roasted chickpeas, yogurt, fruit, boiled eggs, veggies, and plant-based dips, like hummus and guacamole.
  • Go for water or flavored seltzer over juice drinks, soda, and other sugary sips. If you’re not ready to go cold turkey, maybe add a splash of juice to a fizzy water.
  • Plan ahead. One thing that makes ultra-processed foods so appealing is how quickly they cook up on busy weeknights. When you have easy-to-assemble ingredients handy, you don’t need to rely on those kinds of packaged foods to solve your last-minute dinner dilemma. The beauty of planning ahead is that while it may take a little time in advanced, it spares you even more time in the long run, so it’s a strategy that pays off.

WHAT A NUTRITIONIST WANTS YOU TO KNOW

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