A new study found that people who follow a Mediterranean diet—especially those who eat more olive oil and beans—may have stronger immune responses to COVID-19 vaccines. Researchers studied 198 Greek healthcare workers and measured their antibody levels (the body’s defense proteins) several months after vaccination. They discovered that diet quality and certain metabolic health markers were linked to how well the vaccine worked, independent of whether someone had previously had COVID-19. This suggests that what you eat might play a role in how effectively your body responds to vaccines.

The Quick Take

  • What they studied: Whether eating a Mediterranean diet (lots of vegetables, fruits, whole grains, olive oil, and fish) affects how well your body responds to COVID-19 vaccines by measuring protective antibodies
  • Who participated: 198 Greek healthcare workers, average age 48 years old, mostly women, who had received two or three COVID-19 vaccine doses
  • Key finding: People who ate more olive oil and beans, and followed Mediterranean diet patterns more closely, had higher levels of protective antibodies against COVID-19, even after accounting for other factors like age and previous infection
  • What it means for you: Eating a Mediterranean-style diet rich in olive oil and legumes may help your body build stronger protection from COVID-19 vaccines, though more research is needed to confirm this connection

The Research Details

This was a cross-sectional study, which means researchers collected all their information at one point in time rather than following people over months or years. Healthcare workers in Greece answered questions about their diet using a validated questionnaire (a proven tool for measuring what people eat) and had their blood tested 4-6 months after vaccination to measure antibody levels. The researchers used statistical analysis to see which dietary and health factors were connected to stronger antibody responses, while accounting for other important factors like age, smoking, and previous COVID-19 infection.

The study measured antibodies using a standardized laboratory test (CMIA assay), which is a reliable method for detecting the body’s immune response. Researchers also collected information about metabolic health markers—measurements that show how well your body processes food and maintains healthy blood sugar and insulin levels.

Understanding what factors influence vaccine effectiveness is important because it helps us know how to optimize our immune response. While vaccination is the primary tool for protection, this research suggests that lifestyle factors like diet may play a supporting role. This approach is valuable because it looks at real-world factors that people can actually control, rather than just medical interventions.

This study has several strengths: it used validated questionnaires and standardized laboratory tests, it accounted for multiple important factors in the analysis, and it was conducted in a well-characterized population of healthcare workers. However, because it’s a cross-sectional study (snapshot in time), it cannot prove that diet causes better vaccine responses—only that they’re associated. The sample size of 198 is moderate, and the study was conducted in Greece, so results may not apply equally to all populations. Some findings were borderline statistically significant, meaning they need confirmation in larger studies.

What the Results Show

The strongest factors linked to higher antibody levels were having had a previous COVID-19 infection and receiving three vaccine doses instead of two. However, even after accounting for these factors, people who followed the Mediterranean diet more closely had significantly higher antibody levels.

When researchers looked at specific foods, olive oil intake showed the strongest connection to antibodies—people who consumed more olive oil had notably higher protective antibody levels. This relationship held true whether or not people had previously been infected with COVID-19. Legume consumption (beans, lentils, chickpeas) was also independently associated with higher antibodies.

Alcohol intake showed an inverse relationship—people who drank less alcohol tended to have higher antibody levels. Additionally, people with better metabolic health markers (measured by insulin resistance scores) and adequate vitamin D levels showed higher antibodies. Smoking was associated with lower antibody levels.

Vitamin D status showed a borderline significant association with antibody levels, suggesting that maintaining adequate vitamin D may support vaccine response, though this needs further confirmation. The metabolic health marker (METS-IR score) also showed a positive association, indicating that overall metabolic wellness may support immune function. These secondary findings suggest that vaccine response isn’t just about diet alone, but about overall health status.

Very few previous studies have examined the connection between Mediterranean diet and COVID-19 vaccine responses, so this research fills an important gap. The findings align with broader research showing that Mediterranean diet supports immune function and metabolic health. The emphasis on olive oil is particularly interesting because olive oil is known to have anti-inflammatory properties, which may explain why it supports better immune responses.

This study is a snapshot in time, so it cannot prove that diet causes better vaccine responses—only that they’re associated. The study included only Greek healthcare workers, who may differ from other populations in age, health status, and dietary patterns. The sample size of 198 is moderate, which means some findings (like the vitamin D association) are borderline and need confirmation. The study didn’t measure actual infection rates or clinical outcomes, only antibody levels. Additionally, dietary information was self-reported, which can be subject to memory bias or inaccuracy.

The Bottom Line

Based on this research, following a Mediterranean diet pattern—particularly increasing olive oil and legume consumption while limiting alcohol—may support your body’s vaccine response. This is a moderate-confidence recommendation because the study is cross-sectional and needs confirmation through larger, longer-term studies. Additionally, maintaining good metabolic health, adequate vitamin D levels, and avoiding smoking appear to support vaccine effectiveness. These recommendations align with general health guidelines and carry minimal risk.

This research is relevant for anyone who has received COVID-19 vaccines and wants to optimize their immune protection. It’s particularly relevant for older adults, healthcare workers, and immunocompromised individuals who may benefit most from strong vaccine responses. The findings don’t change vaccination recommendations—vaccines remain the primary protection—but suggest that diet may play a supporting role. People with specific health conditions should consult their healthcare provider before making major dietary changes.

This study measured antibodies 4-6 months after vaccination, so benefits would likely develop over weeks to months of following a Mediterranean diet. However, this is the first study of its kind, so we don’t have clear data on how quickly dietary changes might improve vaccine response. Expect to see potential benefits over a period of weeks to months of consistent dietary changes.

Want to Apply This Research?

  • Track daily olive oil consumption (in tablespoons), legume servings, and alcohol intake. Users could set a goal of 2-3 tablespoons of olive oil daily, 1-2 servings of legumes, and limited alcohol, then log actual intake to monitor adherence to Mediterranean diet patterns.
  • Users could set a specific, achievable goal like ‘Add one olive oil-based salad dressing to meals 4 times per week’ or ‘Include beans or lentils in 3 meals per week.’ The app could provide Mediterranean diet recipes featuring olive oil and legumes, with shopping lists and preparation tips.
  • Track Mediterranean diet adherence score weekly using a simple checklist of key components (olive oil, legumes, vegetables, whole grains, fish, limited alcohol). Users could also monitor general health markers like energy levels and overall wellness as indirect indicators of immune health, though antibody testing would require medical visits.

This research suggests an association between Mediterranean diet adherence and vaccine antibody levels but does not prove causation. This study should not replace medical advice or vaccination recommendations. COVID-19 vaccines remain the primary tool for protection against COVID-19. Anyone considering significant dietary changes, especially those with existing health conditions or taking medications, should consult with their healthcare provider first. This research is preliminary and requires confirmation through larger, longer-term studies before making clinical recommendations. Individual results may vary based on genetics, overall health status, and other factors not measured in this study.