An illustration of a chicken with various forms of meat inside.

Different foods take turns being the dietary demon du jour, and currently, processed and “ultraprocessed” foods are the latest to come under the hot glare of scientific scrutiny. It’s certainly warranted.

Research has linked ultraprocessed foods to a higher risk for obesity, heart disease, and cancer. Intriguing new work even suggests that they may actually encourage overeating, possibly because their particular mashup of ingredients disrupts the hormones that control hunger, or it scrambles the gut-brain signals that tell us how much to eat.

Some processing is relatively benign and even enhances healthy properties. But generally speaking, the farther your food gets from its original “whole” version, the less good it is for you.

We’ve illustrated the journey of a few common foods from their least processed to their ultraprocessed forms to show you exactly where and how the nutritional degradation occurs.

Chicken

Usually what you see is what you get when you buy a whole bird or parts, but check the ingredients list. Some brands are plumped up with broth, salt, and various flavors (up to 3 percent by weight for bone-in and 8 percent for boneless). Once you take the chicken home, the seasoning and cooking you do is considered to be a type of processing.

More on Healthy Eating

Ground Chicken
By law, it must be entirely made from the type of poultry specified. Per the USDA’s preference (though not law), it should contain “whole muscle material” (drumsticks, thighs, necks, etc.), and other components, like skin and fat, should be present in “natural proportions.” Other animal parts, like giblets, should be excluded. If the label reads “ground chicken meat,” it can’t contain any skin, and ground chicken breast must be solely breast meat.

Chicken Sausage
The meat and spice mixture that makes up sausage is often stuffed into a casing made from pork. Chicken sausage may have nitrites or nitrates added to prevent bacterial growth and give it color and flavor. These additives, even the natural-sounding “celery powder,” can convert into potentially carcinogenic nitrosamines. Plus, sodium levels tend to be very high.

Chicken Nuggets
This finger food usually consists primarily of breast meat (with or without rib meat) sometimes augmented by dark meat or skin for flavor and texture, and sometimes marinated for flavor. The meat is chopped and formed into “nugget” shapes, which are then seasoned, breaded (generally with refined flour), and fried, often with extra fat and sodium added along the way.

Peanuts in the Shell

After the peanut plants are pulled out of the ground, they’re left to dry in the field for a few days. The peanuts are then removed from the vine and may be further dried under forced hot air. If salted, they have probably been soaked in a brine and dried again.

Roasted Peanuts
Dry-roasted, packaged, ready-to-eat peanuts are shelled, roasted, blanched with hot air or water to remove the skins, and split into halves. If they’re oil-roasted, they’re blanched first and then roasted in oil (coconut, cottonseed, or peanut; the ingredients list will say). Both dry- and oil-roasted peanuts may contain salt. Nutritionally, both types are similar to fresh peanuts in the shell—except for that added sodium.

Peanut Butter
Some of the stuff that comes in jars is minimally processed—it might be ground peanuts with a dash of salt—so you’ll need to stir before use. But many brands on the shelf include hydrogenated oils, in part to keep the peanut butter from separating. And many also contain added sugars.

Peanut Butter Protein Bar
Peanut butter is little more than flavoring in many protein bars, such as Clif Builders Crunchy Peanut Butter Protein Bar. It contains 20 grams of protein, but much of that is from its first ingredient, soy protein isolate, which is protein powder that has been extracted from the soybean and concentrated. Next comes an avalanche of sugars. You don’t get actual peanuts until halfway through the list, which also has peanut flour, salt, soy lecithin, and other additives.

Rolled Oats

Used for oatmeal, rolled oats are lightly processed to make them edible. The oat groats (grain kernels) are steamed, flattened, and dried. They still contain all three parts of the grain—the bran, germ, and endosperm—so they retain all of the fiber and other nutrients. (Even less processed are steel-cut oats, which are simply oat groats sliced into small pieces.) You can buy them with no added sugar, salt, or other ingredients.

Instant Oatmeal
To make oats “instant,” they’re pressed thinner and steamed longer than rolled oats. They’re still a whole grain but can be digested more quickly, which could potentially lead to spikes in blood sugar levels. This processing is light, but more processed versions add sugars, flavorings, and preservatives.

Honey Nut Oat O’s Cereals
Whether name-brand or generic, these healthy-sounding cereals are highly processed. Though the main ingredient is whole oat flour, some may contain three or more forms of sugar, such as sugar, honey, and brown-sugar syrup. Other additives may include salt, oils, and vitamin E as a preservative. Still more egregious, there may be no actual nuts, only “natural almond flavor.”

Oatmeal-Raisin Cookies
The typical packaged cookies are likely to be made primarily with white wheat flour rather than whole oats, and may contain processed ingredients you probably wouldn’t include if you were making them from scratch, such as hydrogenated oil, high fructose corn syrup, whey protein concentrate, and soy lecithin.

An illustration of tomatoes.

Tomatoes

Canned Tomatoes
Picked at peak ripeness, tomatoes destined for canning are washed, prepared (peeled by means of steam or chemicals, then packed whole, diced, crushed, puréed, etc.), and put in liquid (usually water or tomato juice). The cans are heated to kill any bacteria, and then cooled. This processing makes lycopene (an antioxidant in tomatoes that’s linked to a lower incidence of heart disease, prostate cancer, and other diseases) easier to absorb. Additives may include salt, herbs and spices, citric acid, and calcium chloride.

Tomato Pasta Sauce
Like canned tomatoes, those used in jarred or canned sauce are harvested when ripe, then cooked down. Depending on the recipe, however, there may be a lot more than tomatoes in the jar—and not all of it healthy. In CR’s recent test of jarred sauces, about half contained 400 mg of sodium or more per half-cup serving. Many had added sugars, too.

Ketchup
Typical ketchups, made largely of tomato concentrate plus sugars, salt, vinegar, and various spices, can pack a lot of sugar and sodium into a tiny serving. Heinz’s classic, for instance, lists tomato concentrate as its first ingredient, but its third and fourth are high fructose corn syrup and corn syrup, followed by salt and natural flavoring. One tablespoon has 4 grams of sugars and 160 mg of sodium.

Wheat Berries

These are whole-wheat kernels straight off the stalk with the husk removed. Boiling them—which is considered a form of processing—is an easy way to make them edible.

Whole-Wheat Pasta
Both regular and whole-wheat pasta are often made from durum wheat flour (which is higher in protein than some other types of flour), sometimes enriched with iron and B vitamins. But whole-wheat pasta is less processed because it’s made from whole-wheat durum flour, which means it retains the fiber and all the other nutrients in the whole grain.

100% Whole-Wheat Bread
The whole grain in this bread is whole wheat in flour form, and it’s an excellent source of fiber. Homemade bread may consist of little more than flour, yeast, water, and a bit of salt. But packaged whole-wheat breads may contain sugar, wheat gluten, preservatives such as calcium propionate (to prevent mold), and unspecified natural flavors.

“Wheat” or “Honey Wheat” Bread
Wheat bread is most definitely not the same as whole-wheat bread. It may contain some whole-grain flour, but it’s primarily white bread. Made with mostly refined wheat flour, its often lengthy ingredients list may also include sugar, dough conditioners such as sodium, and stearoyl lactylate. A slice usually has just 1 gram of fiber; a whole-wheat slice has 2 to 3 grams.

Editor’s Note: This article also appeared in the January 2020 issue of Consumer Reports magazine.