Scientists reviewed 21 studies to understand how the food we eat affects our brains. They found that eating healthy foods like fish and Mediterranean-style meals helps keep our brains larger and stronger, while eating lots of processed Western-style foods may shrink important brain areas. The research shows that our eating habits and brain health are connected in both directions—what we eat affects our brain, and our brain influences what we want to eat. This discovery could help doctors create personalized eating plans to keep people’s brains healthy as they age.

The Quick Take

  • What they studied: How different eating habits and food choices affect the size and structure of our brains, using brain imaging scans to measure changes
  • Who participated: The review analyzed 21 research studies that included healthy people of all ages from the general population, all using MRI brain scans to measure brain structure
  • Key finding: Healthy diets (especially Mediterranean-style eating with lots of fish) were linked to larger, healthier brain structures, while unhealthy Western-style diets with processed foods were linked to smaller brain areas, particularly in the memory center called the hippocampus
  • What it means for you: Eating better food choices may help protect your brain health and prevent memory problems as you age. However, this research shows connections between diet and brain health, not proof that changing your diet will definitely prevent brain problems—more research is needed to confirm cause and effect

The Research Details

This was a systematic review, which means scientists searched three major medical databases (Scopus, PubMed, and Web of Science) to find all published studies about how eating habits affect brain structure. They carefully selected 21 high-quality studies that met specific criteria: they had to focus on healthy people of all ages, use MRI brain scans to measure the brain, and be published in English up to January 2025.

The researchers then analyzed all these studies together to find patterns and common findings. They looked at what types of diets were studied, how brain structures changed, and whether age or gender made a difference in the results. This approach is like collecting puzzle pieces from different studies to see the bigger picture of how food affects the brain.

A systematic review is important because it combines evidence from many studies rather than relying on just one. This gives us a more complete and reliable picture of the relationship between eating and brain health. By reviewing all available research together, scientists can spot patterns that might not be obvious in individual studies and identify areas where more research is needed.

This review included only studies that used MRI brain imaging, which is a reliable way to measure brain structure. The researchers focused on studies of healthy people, which helps us understand how diet affects normal brain development and aging. However, the review didn’t specify the total number of people studied across all 21 papers, and the individual studies were observational (meaning they tracked what people ate and measured their brains, but didn’t randomly assign people to different diets). This type of study can show connections but cannot prove that diet directly causes brain changes.

What the Results Show

The research found clear patterns showing that what we eat is connected to our brain structure. Healthy eating patterns, particularly the Mediterranean diet (which emphasizes vegetables, fruits, fish, and olive oil) and diets high in fish, were associated with larger brain volumes and thicker brain surfaces. These findings suggest that good nutrition supports brain growth and maintenance.

In contrast, the Western diet—characterized by processed foods, sugar, and unhealthy fats—was linked to smaller brain structures, especially in the hippocampus, which is the brain region responsible for memory and learning. The research also found that gray matter (the thinking part of the brain) was reduced in people following less healthy eating patterns.

Interestingly, specific eating behaviors also mattered. People who practiced restrained eating (carefully controlling portions) and those who genuinely enjoyed their food showed different brain structure patterns. This suggests that not only what we eat, but how we eat and our attitude toward food, may influence brain health.

The effects of diet on the brain varied depending on age and gender, meaning that different age groups and men and women may experience different brain benefits from the same foods. Some diets appeared to protect against brain shrinkage and white matter hyperintensities (small areas of damage in the brain’s communication pathways).

The review revealed that the relationship between eating and brain health is bidirectional—meaning it works both ways. Not only does food affect the brain, but the brain also influences our eating choices and food preferences. This creates a cycle where brain health and eating habits reinforce each other.

The research also highlighted that the timing and consistency of eating patterns matter. Different dietary approaches showed varying levels of protection against age-related brain changes, suggesting that maintaining consistent healthy eating habits over time may be more important than occasional healthy choices.

This systematic review builds on previous research showing that diet affects overall health by specifically examining brain structure. Earlier studies had shown connections between diet and heart health, weight, and disease prevention. This review adds important evidence that these dietary effects extend to the brain itself. The findings align with growing research suggesting that the Mediterranean diet is one of the healthiest eating patterns for brain health, supporting what many previous studies have indicated.

This review has several important limitations to understand. First, all the included studies were observational, meaning researchers watched what people ate and measured their brains, but didn’t randomly assign people to eat different diets. This means we can see that healthy eating and healthy brains go together, but we cannot definitively prove that changing your diet will change your brain structure. Second, the review didn’t provide the total number of people studied across all 21 papers, making it hard to understand the overall strength of the evidence. Third, most studies were likely conducted in developed countries with specific populations, so the findings may not apply equally to all people worldwide. Finally, the studies measured brain structure at one point in time or over short periods, so we don’t know the long-term effects of diet changes on brain health.

The Bottom Line

Based on this research, eating a Mediterranean-style diet rich in fish, vegetables, fruits, and healthy oils appears to support brain health (moderate confidence level). Reducing processed foods and Western-style diet patterns may help protect brain structures as you age (moderate confidence level). However, these recommendations are based on observed connections, not proven cause-and-effect relationships. More research is needed to determine exactly how much diet change is needed and how quickly benefits appear.

Everyone should care about this research, especially people concerned about brain health and memory as they age. This is particularly relevant for middle-aged and older adults, people with family histories of memory problems, and anyone interested in preventive health. However, people with specific medical conditions, eating disorders, or dietary restrictions should consult with their doctor or dietitian before making major diet changes. This research applies to generally healthy people and may not apply to those with certain medical conditions.

Brain structure changes from diet likely happen gradually over months to years, not days or weeks. You probably won’t notice immediate changes in memory or thinking, but consistent healthy eating habits may help protect your brain health over the long term. Most brain benefits from dietary changes would likely appear after several months to years of consistent healthy eating.

Want to Apply This Research?

  • Track daily servings of fish, vegetables, and fruits, aiming for Mediterranean diet components. Record weekly brain-supporting foods (fish 2-3 times per week, colorful vegetables daily, olive oil use) and monitor subjective memory or focus improvements monthly
  • Start by adding one Mediterranean diet element per week: Week 1 add fish, Week 2 add olive oil, Week 3 add more vegetables. Use the app to log these additions and set reminders for meal planning focused on brain-healthy foods
  • Create a monthly check-in to assess energy levels, mental clarity, and focus. Track dietary adherence to Mediterranean-style eating patterns. Consider annual cognitive assessments or memory tests to monitor long-term brain health trends alongside dietary consistency

This research shows connections between eating habits and brain structure but does not prove that changing your diet will definitely prevent brain problems or improve memory. These findings are based on observational studies, not controlled experiments. Before making significant dietary changes, especially if you have medical conditions, take medications, or have a history of eating disorders, consult with your doctor or registered dietitian. This information is for educational purposes and should not replace professional medical advice. If you experience memory problems or cognitive changes, seek evaluation from a healthcare provider.