Whether they know it or not, most Americans cannot go a day – or often a single meal – without eating highly processed foods.
From sugary cereals for breakfast to frozen pizza for dinner, plus potato chips, sodas and ice cream for snacks, highly processed foods make up about 60% of the diet in the United States. For children and teenagers, the proportion is even higher – about two-thirds of their diet.
This is concerning because ultra-processed foods have been linked to a range of negative health effects, from obesity and diabetes to heart disease, depression, dementia and more. A recent study suggests that eating these foods may increase the risk of early death.
However, nutritional science is a difficult matter and most studies to date have found associations but no evidence of the health effects of these foods.
Food manufacturers argue that processing increases food safety and supply and offers a cost-effective, convenient way to provide a varied and nutritious diet.
Even if the science were clear, it’s hard to know what practical advice to give when one study found that ultra-processed foods make up 73% of the U.S. food supply.
The Associated Press interviewed several nutrition experts and here are their answers:
What are ultra-processed foods?
Most foods are processed, whether by freezing, grinding, fermenting, pasteurizing or in other ways. In 2009, Brazilian epidemiologist Carlos Monteiro and his colleagues first proposed a system that classifies foods not by their nutrient content but by their degree of processing.
At the top end of the four-level scale are foods that are produced using industrial processes and contain ingredients such as additives, colors and preservatives that cannot be replicated in the home kitchen, says Kevin Hall, a metabolism and nutrition researcher at the National Institutes of Health.
“These are most, but not all, of the packaged foods you see,” Hall said.
Such foods are often manufactured to be both cheap and irresistibly delicious, says Dr. Neena Prasad, director of Bloomberg Philanthropies’ Food Policy Program.
“They have just the right combination of sugar, salt and fat and you just can’t stop eating them,” said Prasad
However, the degree of processing alone does not determine whether a food is unhealthy or not, says Hall. Whole grain bread, yogurt, tofu and baby formula are all highly processed but still nutritious.
Are highly processed foods harmful?
And here comes the tricky part. Many studies suggest that diets high in such foods are associated with negative health outcomes. But these types of studies can’t say whether the foods are the cause of the negative effects – or whether something else about the people who eat those foods might be responsible.
At the same time, ultra-processed foods as a group tend to contain more sodium, saturated fat and sugar and less fiber and protein. It is not clear whether these effects are due only to these nutrients.
Hall and his colleagues were the first to conduct a small but influential experiment that directly compared the results of similar diets containing highly processed and unprocessed foods.
The study, published in 2019, involved 20 adults living at an NIH center for a month. They were given a diet of ultra-processed and unprocessed foods, balanced in calories, sugar, fat, fiber and macronutrients, for two weeks each, and were allowed to eat as much as they wanted.
When participants ate ultra-processed foods, they consumed about 500 more calories per day than when they ate unprocessed foods, the researchers found – and they gained an average of about 1 kilogram (2.2 pounds) over the study period. When they ate only unprocessed foods during the same period, they lost about 1 kilogram (2.2 pounds).
Hall is currently conducting a more detailed study, but the process is lengthy and expensive, and results are not expected until late next year. He and others argue that such comprehensive research is needed to determine exactly how ultra-processed foods affect consumption.
“It is better to understand the mechanisms by which they cause the adverse health consequences, if they cause them,” he said.
Should highly processed foods be regulated?
Some advocates like Prasad argue that the large body of research linking ultra-processed foods to poor health should be more than enough to persuade government and industry to change their policies. She calls for measures such as higher taxes on sugary drinks, tighter sodium restrictions for manufacturers and a crackdown on the marketing of such foods to children, just as tobacco advertising is restricted.
“Do we want to risk our children getting even sicker while we wait for that clear evidence?” Prasad asked. Earlier this year, FDA Commissioner Robert Califf addressed the issue, telling a conference of food policy experts that ultra-processed foods are “one of the most complex things I’ve ever dealt with.”
However, he concluded: “We must have a scientific basis and then we must implement the measures.”
How should consumers deal with highly processed foods at home?
In countries like the U.S., it’s difficult to avoid highly processed foods – and it’s not clear which ones should be targeted, says Aviva Musicus, scientific director of the Center for Science in the Public Interest, which advocates for food policy.
“The range of highly processed foods is just so wide,” she said.
Instead, it’s better to pay attention to the ingredient list of foods. Check labels and make choices that comply with current U.S. dietary guidelines, she suggested.
“We have really good evidence that added sugar is not good for us. We have evidence that high-sodium foods are not good for us,” she said. “We have good evidence that fruits and vegetables that have been minimally processed are really good for us.”
It is important not to demonise certain foods, she added. Many consumers do not have the time or money to prepare most dishes themselves.
“I think food should be enjoyable and delicious and not require moral judgment,” said Musicus.
