30 August 2019

Ultra-processed poison

Processed foods are much more dangerous to health than was thought

Julia Belluz, Vox: Processed foods are a much bigger health problem than we thought Translated by Alexander Gorlov, XX2 century

For links, see the original article

According to two new studies, the results of which are published in the BMJ, the more ultra-processed (industrially manufactured) food in our diet, the more likely it is to get sick, and even with a fatal outcome. In one of these studies, the use of ultra-processed foods is associated with an increase in cardiovascular diseases, in another – with an increasing risk of dying for any reason.

This work was carried out after the first randomized controlled trial of its kind, carried out by the National Institutes of Health (National Institutes of Health). Then scientists found that people whose diet consists of ultra-processed foods eat about 500 calories more per day than those who consume minimally processed, whole foods.

And no wonder: potato chips, cookies and hot dogs are full of salt, sugar, fat and calories. By consuming these products, we gain excess weight and risk acquiring diseases such as diabetes and obesity. But why? What if ultra-processed food has some unique property that makes us overeat and worsen our health?

A curious answer to this question is given by one of the new hypotheses. Scientists are increasingly coming to the conclusion that processed foods with all their additives, sugar and fiber deficiency can negatively affect the gut microbiome, the trillions of diverse bacteria lining its walls. As a result, the risk of chronic diseases increases and there is a favorable ground for overeating.

This hypothesis requires looking at the harm that ultra-processed foods bring with them from a completely new angle. However, in order to better understand it, we should first find out what ultra-processed foods are and how they form a community of bacteria in the digestive canal that is necessary for our health.

Ultra-processed products from a scientific point of view

Currently, ultra-processed foods account for more than half of the calories consumed by Americans. But what are these products, what is their definition?

Let's start with the fact that ultra-processed foods are very different from the food that our great-great-great-grandmothers ate, as the famous writer Michael Pollan would say. These are frozen chicken nuggets in McDonald's restaurants, soda and sports drinks in almost every stall across the country, as well as Starbucks milkshakes disguised as coffee.

According to the usual scientific definition, these are "products manufactured according to industrial recipes that consist entirely or mainly of substances isolated from food (oils, fats, sugar, starch and proteins), their derivatives (hydrogenated fats and modified starch), as well as substances synthesized in laboratories from food substrates or other organic sources (flavor enhancers, colorants and various food additives that make products appetizing)".

In other words, ultra-processed products are created in factories. They are packed with chemicals and other additives to get the right color, taste, texture and shelf life. This treatment usually leads to an increase in taste, an increase in the caloric content of products and at the same time – to a decrease in the percentage of fiber, vitamins and nutrients. Thus, these products differ from whole (apples, cucumbers, etc.) and processed (pickled vegetables, canned fish in oil, etc.), which depend only on salt, sugar and oil, and not on a number of complex additives used for preservation or flavor enhancement.

Carlos Monteiro, Professor of dietetics and public health at the University of Sao Paulo, participated in the creation of a scientific definition of ultra-processed foods in 2009, when, together with the Brazilian government, he analyzed how the emergence of a global industrial food system affected the consumption of food by the people of this country. Brazilians began to cook less and eat more, while leaning on high-calorie packaged foods. "It became clear to us," Monteiro said in an interview with Vox, "that people preferred ready–to–eat foods made on the basis of sugar, fats and salt, as well as a variety of ingredients intended exclusively for industrial use," such as whey proteins, modified starches and dyes.

That is why it is very difficult to specify exactly what increases the risk of diseases when eating ultra-processed food. Whose fault is it: chemical additives, excessive calorie content, fiber deficiency and other components important for food? Or maybe pollutants are to blame – for example, those that penetrate into food from packaging plastic? In addition, the population that consumes a lot of processed foods may differ significantly from the population that avoids them, and in other parameters. "We are dealing with a very difficult problem," Monteiro added.

What we eat shapes our intestinal flora

Since the advent of ultra-processed foods has fundamentally changed the way we eat, scientists have recently wondered about the impact of these changes on the intestinal microbiome.

Most gut bacteria are harmless or beneficial to our health. They evolved with us, promoting digestion and regulating the immune system. We are only now beginning to understand how necessary this microbiome is for each of us to be healthy. Currently, scientific knowledge about the dependence of health on intestinal bacteria is mainly obtained in the course of studies conducted on mice. The results of studies conducted on humans are overwhelmingly correlative.

Although the reliability of knowledge on this topic leaves much to be desired, there is one provision with which none of the experts argues. Suzanne Devkota, Director of the Microbiome Research Department of the Research Institute of Intestinal Inflammatory Processes and Immunobiology (Inflammatory Bowel and Immunobiology Research Institute) of the F. Vijaya of the Cedars-Sinai Medical Center (Cedars-Sinai F. Widjaja Foundation), expressed it this way: "The main factor determining the composition of our intestinal microbiome is diet." In addition, all experts unanimously claim that the higher the diversity of bacteria in our intestines, the better for our health.

Devkota and a number of other scientists are investigating how an increase in the proportion of processed meat, crushed grain products and sugars in our diet affected the types of bacteria and their diversity in the gut microbiome. The findings of these researchers are worrisome.

Scientists recorded significantly different results by comparing the microbiomes, on the one hand, of mice that consumed a pleasant fatty food with a low fiber content (reminiscent of ultra–processed food popular in the West), and on the other - of mice that consumed fatty food with a high fiber content: it turned out that mice of the first group had a variety of intestinal bacteria and their total number lower than in mice of the second group.

Similar results were obtained in the few studies that were conducted on humans. Scientists took stool samples from hunter-gatherers living in areas with poorly developed industry and therefore almost unfamiliar with ultra-processed foods, and compared them with stool samples from people from industrialized countries. A strong correlation has been found: the farther a person is from modern civilization and ultra-processed foods, the more diverse his intestinal microbiome is.

The researchers who sequenced DNA from calcified plaque came to the same results: they found that people of the Neolithic and medieval times had much more diverse colonies of bacteria in the oral cavity than representatives of the current post-industrial society. "Significant changes in carbohydrate intake that have occurred during the course of human development seem to have had an impact on the ecosystem of the mouth," the researchers noted.

"In general, it can be argued that the microbiota of healthy intestines of representatives of various species has a high level of diversity," says Andrew Gewirtz, professor at the Center for the Study of Infectious Inflammatory Processes and Immunity (Center for Inflammation Immunity and Infection) at the University of Georgia (Georgia State University). "And many [bacteria] tend to disappear with the transition to food with a high degree of processing."

Junk food has a lot of emulsifiers and refined sugars. Perhaps the problem is in them

There is a connection between diets overloaded with ultra–processed foods and dangerous inflammation - when the inflammatory reaction of the body works at the limit of its ability, which makes it difficult for it to fight viruses and diseases. One of the indicators of inflammation is a blood marker called "C-reactive protein" (CRP). Researchers have found a link between elevated levels of CRP and various chronic diseases, including cancer, arthritis, cardiovascular disease and diabetes. And an unhealthy diet, as a rule, increases the level of CRP.

What is the scientific explanation of the connection of ultra–processed foods, on the one hand, with a decrease in the diversity of the microbiome, and on the other - with an increase in the risk of dangerous inflammatory processes and diseases?

According to one theory, key ingredients such as emulsifiers and refined sugar, instead of promoting the prosperity of intestinal microbes, harm them.

Emulsifiers are additives used to stabilize ultra–processed products. They help the oil and vinegar of salad dressings stay in the bottles in a mixed state and prevent the ice cream from solidifying and crystallizing in the freezer. In an article published in 2015, Gewirtz and his colleagues hypothesized that widely used emulsifiers, in particular carboxymethylcellulose and polysorbate-80, are able to destroy the intestinal microbiome and enhance inflammatory processes.

This is exactly what experiments conducted on mice have shown. In mice genetically predisposed to colitis (chronic inflammatory bowel disease), this disease developed faster under the influence of emulsifiers. Mice that did not have such a predisposition, but were also exposed to emulsifiers, showed mild inflammation and mild obesity. According to Gewirtz, microbes useful for the intestine react to emulsifiers as toxic chemicals that are "antagonistic" to the microbiome and lead it to "discord with the host."

"Here is what can be considered a reliable fact: when the dose of emulsifiers in mouse food is about the same as in human, inflammatory processes occur in the intestines of mice," emphasizes Gewirtz. He is now working to conduct a similar study in humans. However, the data obtained on mice turned out to be so convincing that the recommendations on diet for patients with intestinal inflammation suggested avoiding emulsifiers.

According to another theory outlined in a recent review on the impact of the Western diet on the intestinal microbiome, sugar contained in ultra-processed foods can nourish harmful intestinal bacteria, causing their rapid growth.

"These refined carbohydrates," says one of the authors of the review, Marit Zinocker, "can feed harmful bacteria in the small intestine, and it is there that inflammation begins. Animal studies have shown that an increase in the proportion of simple sugars in food affects the growth of [pathogenic] intestinal bacteria."

Zinoker stressed that hypotheses about the role of emulsifiers and refined carbohydrates are just two possible explanations for why ultra–processed foods are harmful to health, and science still has a lot to figure out. At the moment, however, it has already been established that not only what is added to processed foods is harmful to the intestinal microbiome, but also what is missing in them.

The lack of fiber in ultra-processed foods can also be harmful

Since our intestines cannot directly digest fiber, for a long time it was believed that it was useful only for constipation, because by adding volume to the stool, it promotes defecation. But such an idea of the usefulness of fiber prevailed only "until the moment when people [realized] the importance of the indigestible foods we consume for our intestinal bacteria," a microbiologist from the University of Michigan noted in a conversation with me Eric Martens, when I was writing an article about fiber.

From the point of view of modern science, one of the main functions of fiber, useful for our health, is the nutrition of the intestinal microbiome. It's not very clear yet why fiber has a beneficial effect on our intestines, but there are some considerations.

In the gastrointestinal tract, fermentable fiber fibers, which are all soluble and some insoluble, are metabolized or fermented by bacteria. Among the substances that arise during fermentation, there are those that are important food sources for our intestinal bacteria. These are short–chain fatty acids.

They are also good for health, Martens emphasizes. It has been shown that short-chain fatty acids contribute to the production of insulin, so that we have more opportunities to control the level of sugar (or glucose) in our blood with its sharp fluctuations, which, for example, is very important in type 2 diabetes. In addition, these acids seem to have anti-inflammatory properties.

"By consuming little fiber, we are essentially starving our gut microbiome, which for a number of reasons seems to be very harmful," Jens Walter, a researcher studying fiber at the University of Alberta, told me. "Also, we're probably losing [microbiome] diversity."

This lack of diversity, associated with a diet that is low in fiber, can affect the intestinal mucosa. Mucus functions as a protective barrier between our body and the outside world. It is constantly refreshed by secretions from intestinal cells and is covered with a layer of bacteria that make up the intestinal microbiome. According to Gevirtsa, fiber, passing along the upper layer of mucus, nourishes the bacteria living there and thereby supports the normal functioning of the intestinal microbiome.

Another study, conducted again on mice, showed what happens if the bacteria of the digestive tract do not receive fiber. They, as Martens and other researchers found out, begin to corrode the mucus layer, coming into closer contact with the intestinal tissues. "According to our hypothesis," says Martens, "when they stop feeding the microbiome [fiber], bacteria increasingly resort to using the mucous membrane as a source of nutrients."

Do you think it's bad when bacteria eat mucus? You were not mistaken: this is true, because the mucous membrane protects against pathogenic microorganisms. The researchers were able to show that it is easier for a pathogenic microbe to enter the intestine and cause infection if the food has a low fiber content. "The disease develops much faster when there is no mucous membrane," Martens notes. "Its absence causes irritation of [intestinal] tissue and provokes immune reactions," which makes the mouse body more vulnerable to diseases.

Why Microbiome Problems Can Push People to Overeat

According to Gewirtz, in light of the hypothesis about the extremely important role of the intestinal microbiome, it is easier to understand why ultra-processed food forces people to overeat. "Highly processed food negatively affects the microbiota, causing bacteria to starve due to lack of fiber and even attacking them [with emulsifiers]. As a result, the risk of inflammation increases." In such conditions, the body's ability to feel full may weaken, provoking overeating. For example, Gevirtz explained, when consuming food, the body secretes leptin – a hormone that suppresses appetite – but inflammation interferes with the action of leptin.

"In other words," he added, "our results do not cast doubt on the idea of overeating as the cause of the obesity epidemic. We only claim that one of the reasons for overeating is changes in the microbiome that cause inflammation."

Scientists are still far from clear. But is it worth waiting for science to explain exactly why ultra-processed food is harmful before proceeding to regulate its production and consumption?

According to Brazilian Monteiro, it is necessary to act now: legislators should, on the one hand, ensure that unprocessed products are sold everywhere and are inexpensive, and on the other hand, impose taxes on ultraprocessed products and introduce regulation of their marketing.

"We started implementing a policy aimed at eradicating smoking even before we found out all the problems associated with it," Monteiro notes. And now, he argues, health authorities should not wait until all aspects of the harmful effects of ultra-processed food become known. "We are in a situation where we have a lot of ultra–processed foods and a lot of diseases associated with ultra-processed foods," says Monteiro. While we are trying to find out all the properties of these products, we cannot begin to regulate their production and consumption, and since there is more and more evidence that they are harmful, delaying the transition to active action increasingly looks like a position that has an extremely negative impact on people's lives and the work of health authorities.

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