Nov 28, 2024 06:00:00

Scientists are getting to the heart of the question: 'Why are ultra-processed foods so bad for you?'

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Ultra-processed foods ' refers to a group of foods that have been highly processed by industrial methods, including carbonated drinks such as cola, processed meats such as sausages, sweet breads, snacks, retort foods, and cup noodles, which are commonly consumed by modern people. In recent years, many research results have been reported that ultra-processed foods are harmful to health, but the fundamental question of 'Why are ultra-processed foods bad for the body?' remains unclear, and scientists are trying to solve the mystery in various ways, reports The Economist, a political and economic magazine.

Scientists are learning why ultra-processed foods are bad for you
https://www.economist.com/science-and-technology/2024/11/25/scientists-are-learning-why-ultra-processed-foods-are-bad-for-you

Humans have a long history of food processing, and over 3,000 years ago in Mexico and Central America, the method of treating corn kernels with lime water or lye was invented. Nixtamalized corn has higher nutritional value, and removing the husk during the process makes it easier to grind into flour.

In the 19th century, canning was invented and pasteurization techniques became widespread, leading to industrial-scale food processing. Innovations in processing techniques made food cheaper and more abundant, and the average daily food supply available to people in developed countries increased by more than 20% between 1961 and 2021, reaching 3,500 kcal per person. At the same time, obesity rates have more than tripled during the same period, exacerbating health problems associated with obesity.

Among these foods, a group of foods known as 'ultra-processed foods' is believed to be involved in various health problems. Carlos Monteiro, professor emeritus at the University of Sao Paulo in Brazil, coined the term, noting that in the early 21st century, Brazilians were buying less sugar and oil than before, yet the incidence of obesity and metabolic diseases was on the rise. This increase in obesity and metabolic diseases coincided with the rise in popularity of pre-packaged snacks and retort foods rich in additives such as sugar and fat.

In 2009, Monteiro proposed the

Nova classification , which classifies foods into four groups based on the degree of processing. The four groups based on the Nova classification are as follows:

Group 1: Processed or Minimally Processed Foods
Foods that are harvested or caught in their original state or that have been minimally processed (e.g., removed, crushed, dried, pasteurized, etc.) include grains, fruits, vegetables, beans, meat, fish, eggs, milk, plain yogurt, and spices.

Group 2: Processed food ingredients
Foods that have been processed by pressing, refining, milling, etc. on foods in Group 1. Includes vegetable oils, salt, sugar, vinegar, starch, honey, and syrups extracted from wood.

Group 3: Processed foods
Group 3 consists of relatively simple processed foods that are made by adding seasonings to the non-processed foods in Group 1, baking, boiling, canning or bottling, or non-alcoholically fermenting them. These include canned vegetables and fish, nuts with added salt, fruits in syrup, dried fish, and simple bread.

Group 4: Ultra-processed foods
Processed foods are foods that have been highly processed by adding substances that are not used in normal cooking, such as hardened oils, modified starches, isomerized sugars, artificial colorings, and sweeteners. These include soft drinks such as cola, concentrated fruit juices, margarine, processed meats, sweet breads, candy, retort foods, frozen foods, and instant noodles.

Since the 1990s, the proportion of ultra-processed foods in the global diet has increased, and at the time of writing, ultra-processed foods account for more than half of the calorie intake in the United States and the United Kingdom. Recent studies have linked ultra-processed foods to metabolic syndrome, cancer, cardiovascular disease, mental health problems, and increased overall mortality.

Fast food, snacks and other 'ultra-processed foods' are linked to 32 adverse health effects, including metabolic syndrome and mental illness - GIGAZINE

Scientists agree that ultra-processed foods are bad for health, but there is debate as to why they are bad for health. Some say that ultra-processed foods are unhealthy because they have low nutritional value, but there are also some ultra-processed foods that are highly nutritious, so some say that the manufacturing process of ultra-processed foods itself poses some risks.

Reaching definitive answers through observational studies alone is difficult, because factors that explain poor health include not only diet but also income, education, and socioeconomic status. A promising option is a randomized controlled trial , in which researchers track participants' food intake and control for all other variables.

In a 2019 study , Kevin Hall, a researcher at the National Institutes of Health (NIH), conducted a randomized controlled trial in which 20 subjects stayed at the NIH Clinical Center for four weeks and were asked to eat either an ultra-processed food diet or a minimally processed food diet every two weeks. During the experiment, subjects were allowed to eat as much as they wanted and were provided with sufficient calories, sugar, fiber, fat, and other nutrients.

The study found that subjects who ate only ultra-processed foods consumed about 500 more calories per day than subjects who ate only minimally processed foods. They also ate faster and gained an average of 1kg in weight over the two weeks, while subjects who ate only minimally processed foods lost about 1kg in weight over the two weeks.

These results suggest that the reason why ultra-processed foods worsen people's health is not just because of the excess salt, fat, and sugar, but also because ultra-processed foods make it easy to eat more calories than you need. Possible reasons for overeating ultra-processed foods include the increased energy density per bite during the manufacturing process and the combination of flavor and nutrients that make them a luxury item.

Based on the results of his 2019 study, Hall has begun a new study in which 36 subjects will be asked to follow a specific diet and track their progress for one month. In addition to the 'ultra-processed food only diet' and 'minimally processed food only diet' prepared in the 2019 study, this study will also prepare a 'diet of ultra-processed foods only with low energy density and palatability' and a 'diet of ultra-processed foods only with high energy density but low palatability' to investigate what changes will occur within the same ultra-processed foods.

While the full results of the study are not expected to be published until 2025, early findings suggest that both the energy density and palatability of ultra-processed foods drive excess calorie intake, while it remains unclear how to mitigate the harms of these foods.

The Economist points out that the Nova classification system has shortcomings, such as the fact that the presence of chemical additives alone classifies foods as ultra-processed regardless of the amount, and that breakfast cereals, breads, and yogurt with fruit, which are considered to be less harmful to health, are also included in ultra-processed foods. 'The insights from Dr. Hall's research will help us better understand ultra-processed foods and may pave the way for more balanced and useful guidelines,' he said.