A sandwich made with cold cuts.

R eading nutrition labels on packaged foods is probably high up on most nutritionists’ lists of healthy eating tips. But it’s just as important to check out the ingredients list. “It’s a good way to judge the quality of a food,” says Charlotte Vallaeys, M.S., senior policy analyst and a nutritionist at Consumer Reports. “And a long list of food additives is a sign that a food is highly processed.” 

According to the Food and Drug Administration, there are more than 3,000 additives used in foods to—among other things—enhance flavor, texture, or shelf life. They range from simple ingredients like sugar or salt to chemical compounds with unpronounceable names. You certainly don’t need to avoid them all, but even among additives that the FDA has deemed safe, there is some evidence that not all are completely benign. We’ve taken a look at the latest research on some food additives that have recently sparked some controversy or concern.

Nitrates and Nitrites

These food additives are used mainly as preservatives in processed meats—like bacon, hot dogs, and deli meats.

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What’s the concern? When these foods are cooked at high heat, say, when you fry bacon or grill a hot dog, or when they mix with stomach acid during digestion, the added nitrites can generate nitrosamines. Nitrosamines may be carcinogenic, and some research shows that eating as little as half an ounce of deli meat or half a hot dog daily increases the risk of premature death. Even if the package says no nitrates or nitrites added, processed meats probably still contain them. That’s because per Department of Agriculture regulations, that claim is permitted if the meat is cured with natural sources of nitrates/nitrites, such as celery, instead of synthetic ones, such as sodium nitrate or nitrite. “No matter the source, though, the compounds are chemically identical and have the same health effects,” Vallaeys says.

Trehalose

A type of sugar, trehalose enhances flavor by adding a mild sweetness to foods (it’s about half as sweet as sugar). It’s also used to extend a product’s shelf life and improve texture. We consume small amounts naturally in foods like mushrooms, yeast, and shellfish, but it’s found in far higher concentrations in processed foods. Since trehalose was approved by the FDA in 2000, it’s been used in a variety of products, such as baked goods, cereals, fish in pouches, and frozen shrimp.

What’s the concern? A study published in the journal Nature found a connection between the sweetener and Clostridioides difficile (C. diff) infections. C. diff causes inflammation of the colon and diarrhea, and is potentially deadly. When you eat high amounts of trehalose, “the enzymes that break it down in our bodies get overwhelmed,” says study author Robert Britton, Ph.D., professor in the department of molec­ular virology and microbiology at Baylor College of Medicine. Consuming trehalose doesn’t transmit the bacteria, he says, but it encourages its growth. And anyone who’s taking an antibiotic—which typically wipes out the good bacteria that keep C. diff in check along with ridding your body of infection—can be at risk. Britton cautions that his findings aren’t cause to eliminate trehalose from your diet if you’re healthy, because otherwise healthy people don’t get C. diff, and even in those who are susceptible (such as people in hospitals or long-term-care facilities), avoiding trehalose isn’t a cure. But, he says, “the hope is that it will reduce the strains that are causing more disease and killing more people.”

Carrageenan

Derived from red seaweed, carrageenan is used as a stabilizer (to keep items like salad dressing from separating) and to give products like frozen desserts, yogurts, and plant milks a creamy taste and texture.

What’s the concern? The structure of carrageenan is foreign to human cells, and exposure to it causes inflammation, says Joanne Tobacman, M.D., associate professor of clinical medicine at the University of Illinois at Chicago, who has studied carrageenan extensively. The inflammation often affects the gastro­intestinal tract, and some people with inflammatory digestive conditions, such as irritable bowel syndrome, report symptom relief when they avoid carrageenan. But according to Tobacman, carrageenan may have an effect on inflammation elsewhere in the body, too. “Inflammation is involved in many disease processes—including cancer, arthritis, and diabetes.”

Consumer Reports and the National Organic Standards Board called for removal of carrageenan in organic products due to its questionable safety. But the USDA decided to continue to allow carrageenan in organic products. The good news is that the additive has already disappeared from many organic products. “Thanks to customer demand, you may be more likely to find a ‘no carrageenan’ claim on the front of an organic food package than you are to find an organic product that contains it,” Vallaeys says. But carrageenan can still be found in many nonorganic foods, so check ingredients lists.

Artificial Sweeteners

These sugar substitutes, such as acesulfame potassium (Ace K), aspartame, and sucralose, are much sweeter than sugar and have few or no calories.

Because they’re used in “diet” foods, you may you think that if you don’t eat such products, you aren’t consuming any artificial sweeteners. But some, especially sucralose, are showing up in a variety of regular products—quite possibly because food manufacturers must now list how many grams of added sugars a product contains. “Manufacturers may use sugar and an artificial sweetener to maintain a certain level of sweetness, while keeping the total grams of added sugars low,” says Amy Keating, R.D., a dietitian at CR.

What’s the concern? Some research suggests that artificial sweeteners may be associated with increased risk of heart disease and type 2 diabetes, and may cause harmful changes in the gut microbiome. And although many people turn to artificial sweeteners in an effort to help them lose weight, several studies have found that consuming artificially sweetened foods instead of sugar-sweetened ones may not actually lead to weight loss.

One small study, by researchers at George Washington University, delved deeper into the connection between artificial sweeteners and body fat. When seven overweight or obese women drank three cans of diet soda that contained sucralose and Ace K per day for eight weeks, they had increased inflammation in fat cells. One consequence of this may be that it leads to changes in the way the body uses insulin, preventing glucose from entering the cells. “In an obese or insulin-resistant individual, excess glucose gets stored as fat,” says study author Sabyasachi Sen, M.D., associate professor of medicine at George Washington University School of Medicine. In addition, the researchers saw changes that suggest that drinking diet soda may lead to the creation of more fat cells.

What about stevia? It’s known as a “natural” low-calorie sweetener—in fact, products that contain it often claim “no artificial sweeteners” on the package. Still, Vallaeys says, though the starting material may be a plant, stevia extracts are highly processed. And the evidence that stevia aids in weight loss or lowering blood sugar levels is very limited.

Sorbitol

Sorbitol is a sugar alcohol that has about half the calories of sugar but also about half the sweetness. It’s used as a sweetener in sugar-free versions of foods like candy, cookies, and gum, as well as an emulsifier and anti-caking agent in some products. But it also occurs naturally in some dried fruits—particularly prunes.

What’s the concern? “Sorbitol brings water into the colon and acts as a laxative,” says Dana Hunnes, Ph.D., R.D., M.P.H., senior clinical dietitian at Ronald Reagan UCLA Medical Center. “That’s not necessarily a bad thing, but at high doses it can have unwanted side effects, such as bloating, gas, and diarrhea.”

Phosphates

Phosphates are a form of phosphorus, a mineral that supports bone health. But phosphorus-containing additives, such as phosphoric acid and disodium phosphate, are found in a variety of processed foods—including soda, baked goods, dairy products, and fast food. Phosphorus from additives is more readily absorbed than when it occurs naturally in food.

What’s the concern? High phosphorus intake is hazardous for people with kidney disease or those at risk for it. “If kidney function is impaired, getting too much phosphorus puts extra strain on the kidneys to try to excrete it,” Hunnes says. But even those with healthy kidneys should be cautious about eating too many foods with phosphate additives. Too much phosphorus can bind to calcium, pulling it from bones and leaving them brittle. And researchers have found a link between high phosphate levels and increased cardiovascular risk. A 2013 study in the U.K. of more than 700,000 people found that those with normal kidney function but high phosphorus levels had a 36 percent increased risk of a cardiovascular event (such as a stroke or heart attack) over those with normal phosphorus levels.

Sodas and baked goods may have phosphorus-containing additives, which have been linked to kidney and heart problems.

Editor’s Note: This article also appeared in the September 2020 issue of Consumer Reports On Health