The case against processed food just keeps getting stronger. But, amazingly, we still don’t understand exactly why it’s so bad for us.
In two new papers published in the BMJ, the more ultraprocessed — or industrially manufactured — foods a person ate, the more likely they were to get sick and even die. In one study, they were more likely to suffer from cardiovascular problems. The other linked an ultraprocessed diet to a higher risk of death from all causes.
Those studies followed a first-of-its-kind randomized controlled trial, out of the National Institutes of Health: Researchers found people following an ultraprocessed diet ate about 500 more calories per day than those consuming minimally processed, whole foods.
Sure, potato chips, cookies, and hot dogs are chock-full of salt, sugar, fat, and calories. They can cause us to gain weight and put us at a higher risk of diseases such as diabetes and obesity. But why? What if there’s something unique about ultraprocessed foods that primes us to overeat and leads to bad health?
A new, intriguing hypothesis offers a potential answer. Increasingly, scientists think processed foods, with all their additives and sugar and lack of fiber, may be formulated in ways that disturb the gut microbiome, the trillions of diverse bacteria lining our intestines and colon. Those disturbances, in turn, may heighten the risk of chronic disease and encourage overeating.
The idea sheds new light on why ultraprocessed foods seem to be so bad for us. But to understand the hypothesis, we need to first look at what ultraprocessed foods are, and how they shape the community of bacteria in our gut that’s so intimately linked to our health.
Ultraprocessed Foods, Explained
More than half of the calories Americans consume now come from ultraprocessed foods. But what exactly are they?
For starters, ultraprocessed foods look a lot different from the foods our great-great-great-grandmothers ate, as author Michael Pollan would say. They’re the frozen chicken nuggets at McDonald’s, the soda and sports drinks in just about every beverage fountain across the country, and the milkshakes masquerading as coffee at Starbucks.
According to a widely used scientific definition, they’re:
industrial formulations made entirely or mostly from substances extracted from foods (oils, fats, sugar, starch, and proteins), derived from food constituents (hydrogenated fats and modified starch), or synthesized in laboratories from food substrates or other organic sources (flavor enhancers, colors, and several food additives used to make the product hyper-palatable).
In other words, ultraprocessed foods are created in factories. They’re pumped full of chemicals and other additives for color, flavor, texture, and shelf life. This processing generally increases the flavor and caloric density of the foods, while stripping away the fiber, vitamins, and nutrients. So these foods are distinct from whole foods (like apples and cucumbers) and processed foods (like vegetables pickled in brine, or canned fish in oil) that rely on only salt, sugar, and oil — rather than a range of complicated additives — to preserve them or make them tastier.
Carlos Monteiro, a professor of nutrition and public health at the University of Sao Paulo, helped write the “ultraprocessed” definition in 2009, when he was working with the Brazilian government to understand how the emergence of a global industrial food system changed Brazilians’ eating habits. People started cooking less, eating out more, and relying on packaged products for their calories. “We realized that people were replacing freshly prepared dishes and meals,” he told Vox, “[with] ready-to-consume products based on sugar, fats and salt plus many ingredients of exclusive industrial use,” such as protein isolates, modified starches, and color additives.
That’s why pinpointing exactly what in ultraprocessed foods may increase the risk of disease is difficult. It’s hard to disentangle, for example, whether it’s the chemical additives in these foods, the calories they deliver, or the stuff they generally don’t contain, such as fiber. Or maybe it’s the contaminants in them, like plastics that leach from packaging. People who eat lots of processed foods may also be fundamentally different from people who avoid them. “We are dealing with something very complex,” Monteiro added.
What we eat shapes our gut flora
Considering the arrival of ultraprocessed foods fundamentally changed how we eat, researchers recently began to wonder what that was doing to our gut microbiome.
The majority of bacteria in our gut are benign or good for our health. They evolved with us to do things such as aid digestion and regulate the immune system. We’re only just beginning to understand how integral the microbiome is to our health. And to date, much of the science on the relationships between these bacteria and our health is focused on mice. Of the studies we have in humans, most of the findings are correlational.
But there’s one thing researchers already agree on: “Diet is the No. 1 influencer and determinant of our gut microbiome composition,” said Suzanne Devkota, director of microbiome research at the Cedars-Sinai F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute. They also generally agree that the more diversity of bacteria in the gut microbiome, the better for our health.
Devkota is among the researchers exploring how the influx of processed meats, cereals, and sugars into our diet has influenced both the type of bacteria and variety of them in the microbiome. Their findings are potential cause for concern.
When researchers have compared the microbiomes of mice eating a bland, low-fiber, high-fat diet (one that resembles Western-style, ultraprocessed food) to mice eating a fiber-enriched high-fat diet, the two sets of rodents had distinctly different microbiomes: Mice on the low-fiber diet had a marked reduction in the total numbers of bacteria in their gut and a less diverse microbiome compared to the mice on the high-fiber diet.
The mouse findings echo the few studies we have in humans. Researchers who analyzed stool samples from people living in less industrialized hunter-gatherer cultures — where ultraprocessed foods are uncommon — and compared them with stool samples from people in industrialized countries, uncovered a strong pattern: The further away people were from industrialization and ultraprocessed foods, the more diverse their gut micriobiome was.
Similarly, when researchers sequenced the DNA of calcified dental plaque, they found the bacterial colony in the oral cavities of humans from Neolithic and medieval times were a lot more diverse than postindustrial modern humans. “Major changes in carbohydrate intake in human history appear to have impacted the ecosystem of the mouth,” the researchers wrote.
“The thing you can generally say is that in states of health, the microbiota has a high level of diversity in a wide variety of different species,” said Andrew Gewirtz, a professor at Georgia State University’s Center for Inflammation Immunity and Infection. “And a lot of these [bacteria] tend to get lost in diets that are highly processed.”
There’s also a link between diets heavy in ultraprocessed foods and harmful inflammation — when the body’s inflammatory response goes into overdrive, making it harder to fight off viruses and disease. One measure of inflammation is a blood marker called C-reactive protein (CRP). Researchers have found associations between higher levels of CRP and various chronic illnesses, including cancer, arthritis, cardiovascular disease, and diabetes. And people who eat an unhealthy diet tend to have higher levels of CRP in their bodies.
So why exactly are these foods linked to less diversity in the microbiome, and more inflammation and disease?
Read the full article here: https://www.vox.com/science-and-health/2019/6/11/18652653/diet-weight-loss-ultra-processed-foods-microbiome
