Researchers studied over 22,000 people to understand why ultra-processed foods (like packaged snacks and fast food) might be bad for our health. They discovered that these foods are missing important plant compounds called polyphenols that help reduce inflammation in our bodies. When people ate more ultra-processed foods, they had less of these protective compounds in their diet and showed signs of more inflammation. The study suggests that one major reason ultra-processed foods harm us is because they lack these beneficial plant chemicals that our bodies need to stay healthy.

The Quick Take

  • What they studied: Whether the lack of plant-based protective compounds (called polyphenols) in ultra-processed foods explains why these foods cause inflammation in the body
  • Who participated: 22,169 Italian adults with an average age of 55 years, ranging from younger to older adults, studied between 2005-2010
  • Key finding: People who ate more ultra-processed foods had about 132 milligrams less polyphenols per day and showed higher inflammation markers. When researchers accounted for polyphenol intake, it explained about 18% of why ultra-processed foods cause inflammation
  • What it means for you: Eating more whole foods like fruits, vegetables, nuts, and beans—which are rich in polyphenols—may help reduce body inflammation and protect your health. This suggests one important reason to limit packaged and processed foods is their lack of these protective plant compounds

The Research Details

This was a cross-sectional study, which means researchers looked at information from a large group of people at one point in time (2005-2010) rather than following them over many years. The researchers asked participants about their eating habits and then matched their food choices to a database of plant compounds to calculate how many polyphenols they consumed. They also measured inflammation in the blood using a special scoring system called the INFLA-score, which combines several inflammation markers into one number.

The study classified foods using the NOVA system, which divides foods into four groups: unprocessed natural foods, processed foods with added ingredients, ultra-processed foods (like packaged snacks and fast food), and other items. Researchers then looked at whether people who ate more ultra-processed foods had lower polyphenol intake and higher inflammation levels.

This research design is important because it helps identify potential explanations (called ‘pathways’) for why certain foods harm health. By measuring both ultra-processed food intake and polyphenol content at the same time, researchers could see if the missing plant compounds might be the reason ultra-processed foods cause inflammation. This type of study is a good first step before doing more expensive and time-consuming long-term studies.

The study included a large, diverse group of over 22,000 people, which makes the findings more reliable. The researchers adjusted their analysis for many other factors that affect inflammation (like age, exercise, smoking, and overall diet quality) to isolate the effect of polyphenols. However, because this is a cross-sectional study, it shows associations rather than proving cause-and-effect relationships. The study was conducted in Italy, so results may not apply equally to all populations worldwide.

What the Results Show

The research found a clear pattern: people who ate more ultra-processed foods consumed significantly fewer polyphenols—about 132 milligrams less per day compared to those eating the least ultra-processed foods. This pattern held true across all major types of polyphenols studied.

When researchers looked at inflammation levels, they found that higher ultra-processed food consumption was directly linked to higher inflammation markers. However, when they added polyphenol intake into their analysis, the connection between ultra-processed foods and inflammation became weaker. This suggests that the missing polyphenols explain part of why ultra-processed foods cause inflammation.

Specifically, polyphenols explained about 18% of the harmful effect of ultra-processed foods on inflammation. One type of polyphenol called lignans was particularly important, explaining about 33% of the effect. This means that while missing polyphenols are an important reason ultra-processed foods cause inflammation, other factors (like additives, salt, sugar, and unhealthy fats) also play a role.

The study found that the relationship between ultra-processed foods and inflammation was consistent across different groups of people, suggesting this is a widespread pattern. Different classes of polyphenols (including flavonoids and phenolic acids) all showed similar protective effects against inflammation. The findings were strongest in people with the highest ultra-processed food consumption, indicating that the more of these foods people eat, the more pronounced the inflammation problem becomes.

Previous research has shown that ultra-processed foods are linked to inflammation and chronic diseases like heart disease and diabetes. This study adds an important piece to that puzzle by identifying that the lack of polyphenols is one specific mechanism explaining this connection. Other studies have shown that polyphenol-rich foods (like berries, tea, and olive oil) reduce inflammation, and this research confirms that polyphenol content is one key difference between healthy whole foods and ultra-processed alternatives.

Because this study looked at people at one point in time rather than following them over years, we cannot prove that ultra-processed foods directly cause inflammation—only that they’re associated with it. The study relied on people’s memory of what they ate, which can be inaccurate. The research was conducted in Italy, so the findings may not apply equally to people in other countries with different food cultures. Additionally, the study cannot rule out that other unmeasured factors might explain the relationship between ultra-processed foods and inflammation.

The Bottom Line

Based on this research (moderate confidence level): Limit ultra-processed foods like packaged snacks, fast food, and sugary drinks. Increase consumption of whole foods rich in polyphenols, including fruits (especially berries), vegetables, nuts, seeds, whole grains, legumes, tea, and olive oil. These changes may help reduce inflammation in your body. The evidence suggests these changes could be particularly important for people at risk of heart disease, diabetes, or other inflammation-related conditions.

Everyone should consider these findings, but they’re especially relevant for people concerned about heart health, those with family histories of chronic disease, and anyone looking to reduce inflammation. The findings apply to adults, though the study focused on middle-aged and older adults. People with specific health conditions should consult their doctor before making major dietary changes.

Inflammation reduction from dietary changes typically takes several weeks to a few months to become measurable in blood tests. You may notice improvements in energy, digestion, or how you feel within 2-4 weeks of consistently eating more polyphenol-rich foods and fewer ultra-processed foods. Long-term benefits for disease prevention develop over months and years of sustained healthy eating.

Want to Apply This Research?

  • Track daily servings of polyphenol-rich foods (berries, leafy greens, nuts, legumes, tea) and ultra-processed food servings. Aim to increase polyphenol-rich foods to 5+ servings daily while reducing ultra-processed foods to fewer than 2 servings per day. Monitor changes in energy levels and digestion over 4-8 weeks.
  • Set a specific goal like ‘Replace one packaged snack daily with a polyphenol-rich alternative’ (example: swap chips for a handful of almonds and berries). Use the app to log these swaps and build the habit gradually. Create reminders to prepare polyphenol-rich snacks in advance.
  • Weekly check-ins on polyphenol food intake and ultra-processed food reduction. Monthly reflection on how you feel (energy, digestion, inflammation symptoms). If available, track inflammation markers through blood tests every 3-6 months with your healthcare provider to see if dietary changes are working for you.

This research shows an association between ultra-processed foods, low polyphenol intake, and inflammation, but does not prove cause-and-effect. Individual results vary based on genetics, overall lifestyle, and other health factors. This information is for educational purposes and should not replace professional medical advice. If you have existing health conditions, take medications, or are considering significant dietary changes, consult your healthcare provider or registered dietitian before making changes. This study was conducted in a specific population and may not apply equally to all groups.