The Mediterranean diet is one of the most studied eating patterns in the world. A new study, published in October 2026 in The American Journal of Clinical Nutrition, adds an important piece: a “signature” of 67 small molecules measured in the blood, which reflects what people actually eat, is linked to a lower risk of death over more than a decade. In the long run, this kind of measure could let a blood test show whether a healthier diet is really making a difference inside the body.
What the new study found
The team, led by Estefanía Toledo (University of Navarra, Spain) with Frank Hu (Harvard T.H. Chan School of Public Health), started from a tool created in 2020: a blood signature made of 67 metabolites, small molecules the body produces or transforms from food. The signature was designed to reflect how closely someone follows a Mediterranean diet and had already been linked to a lower risk of heart disease.
This time, the researchers checked whether it could also predict long-term survival in two very different groups:
| Group studied | Participants | Follow-up | Main result |
|---|---|---|---|
| PREDIMED trial (Spain), older adults at high cardiovascular risk | 1,880 | About 13 years | 23% lower risk of death in the top third of signature scores vs the bottom third |
| Three large US cohorts of nurses and health professionals | 12,704 | About 25 years | 23% lower risk of death in the top fifth vs the bottom fifth |
These results account for age, smoking, body weight and existing conditions. In the Spanish group, the link held even after accounting for what participants reported eating, which means the blood signature adds information that food questionnaires miss. According to a summary in News-Medical, each one-standard-deviation rise in the signature was tied to about a 19% lower risk of death in PREDIMED, and the clearest link was with deaths from cardiovascular disease.
Why measure diet in the blood?
Most nutrition studies rely on questionnaires that ask people what they ate. Memory is imperfect, portions are hard to estimate, and bodies respond differently to the same foods. A blood signature gets around part of that: it reflects both what was eaten and how the body processed it. Most of the 67 molecules are lipids (fat-related molecules); some track with olive oil intake, and others are long-chain fatty acids found in nuts and fish.
What the study does not say
- This is an observational study: it shows an association, not cause and effect. It does not prove that raising your signature would extend your life.
- Changes in the signature over the first year of follow-up were not linked to mortality; only the measured level was.
- The US participants were mostly white health professionals in relatively good health, so the findings need to be confirmed in more diverse groups.
- Measuring these 67 metabolites is a research tool. There is no routine lab test for this signature today.
The Mediterranean diet in practice
The Mediterranean diet is not a weight-loss plan but a way of eating: plenty of vegetables, fruit, beans and lentils, whole grains and nuts, olive oil as the main fat, fish regularly, and little red meat, processed meat and sugary foods. This overlaps with the heart-healthy eating advice of the National Heart, Lung, and Blood Institute (NHLBI): more fruits, vegetables, whole grains, fish and nuts, and less saturated fat, sodium and added sugar.
Which tests can monitor or screen for this?
The 67-molecule signature is not available in routine care, but several common blood tests already show how your diet is affecting your heart and metabolic health:
- a lipid panel, with LDL cholesterol, HDL cholesterol and triglycerides;
- fasting glucose and HbA1c, which reflect blood sugar;
- C-reactive protein (CRP), a marker of inflammation;
- a comprehensive metabolic panel if your doctor finds it useful.
Comparing these results from one blood draw to the next, after several months of eating differently, lets you see what is actually changing.
What this means for you
This study does not change dietary advice: it backs it up with a biological measure that is more objective than questionnaires. The practical message stays the same: adopt the basics of the Mediterranean diet gradually and stick with them. Researchers hope that in the future, signatures like this one will help spot people whose diet is not having the expected effect on their body, so advice can be more personal.
Latest scientific advances
Recent research points in the same direction: what we eat leaves a measurable trace in the blood and urine, and that trace says a lot about future health.
- A large US study published in 2024 in JAMA Network Open, which followed thousands of women for about 25 years, found that strong adherence to the Mediterranean diet was linked to lower mortality. Part of the benefit ran through measurable markers: less inflammation, better insulin sensitivity and healthier blood fat profiles.
- In 2025, PREDIMED researchers built a urine signature of polyphenols, protective compounds found in olive oil, nuts, fruit and vegetables. The higher the signature, the lower the cardiovascular risk.
- Also in 2025, a UK Biobank analysis of people with fatty liver disease found that blood omega-3 fatty acids explained part of the Mediterranean diet’s benefits.
- In 2026, an Australian analysis in Nature Communications identified blood lipid fingerprints specific to different foods (dairy, meat, fish) and linked them to cardiometabolic health.
For you, this means the effect of a better diet is not just a feeling: at least part of it shows up in blood tests.
When to see a doctor
Talk to your GP before a major change in diet if you have diabetes, kidney disease, liver disease, take a blood thinner, or are already treated for high cholesterol. Also see a doctor if your results show high LDL cholesterol, triglycerides, blood sugar or CRP, or if you are losing weight without trying. A registered dietitian can help you adapt the Mediterranean diet to your tastes and budget.
Glossary
- Metabolite: a small molecule produced or transformed by the body, for example from food.
- Metabolomics: measuring hundreds of metabolites at once in a blood or urine sample.
- Metabolic signature: a combination of metabolites that together reflect a habit, here diet.
- Observational study: a study that observes links without intervening, and so cannot prove cause and effect.
- PREDIMED: a large Spanish trial that compared the Mediterranean diet with a low-fat diet in adults at high cardiovascular risk.
Frequently asked questions
Can I get a blood test for the Mediterranean diet signature?
Not yet. The 67-metabolite signature is a research tool. Routine tests such as a lipid panel, HbA1c and CRP are the practical way to follow the effect of your diet.
Does a high signature mean I will live longer?
No. The study describes differences in risk between groups, not an individual’s lifespan.
How long before diet changes show up in my blood work?
Cholesterol and triglycerides can shift within a few months; HbA1c reflects roughly the last three months of blood sugar. Your doctor can tell you when to recheck.
Do I have to eat fish to follow a Mediterranean diet?
Fish is a regular part of it, but the pattern as a whole matters most: vegetables, legumes, whole grains, nuts and olive oil.
Sources
- Toledo E, Rovayo A, Li J, et al. A metabolomic signature of the Mediterranean diet predicts mortality in 4 independent cohorts. The American Journal of Clinical Nutrition, 2026. DOI: 10.1016/j.ajcnut.2026.101496
- News-Medical. Scientists found a link between Mediterranean diet blood markers and longer survival, 20 October 2026
- ScienceAlert. Scientists found a blood signature linked to 23% lower risk of death, October 2026
- Li J, Guasch-Ferré M, et al. The Mediterranean diet, plasma metabolome, and cardiovascular disease risk. European Heart Journal, 2020. DOI: 10.1093/eurheartj/ehaa209
- Ahmad S, Moorthy MV, Lee IM, et al. Mediterranean Diet Adherence and Risk of All-Cause Mortality in Women. JAMA Network Open, 2024. DOI: 10.1001/jamanetworkopen.2024.14322
- Domínguez-López I, Galkina P, Fernández-Duval G, et al. Urinary polyphenol signature of the Mediterranean diet is associated with lower cardiovascular disease risk: the PREDIMED trial. BMC Medicine, 2025. DOI: 10.1186/s12916-025-04587-w
- Wang K, Xiang S, He Q, et al. Mediterranean diet and associated metabolite signatures in relation to MASLD progression. Hepatology Communications, 2025. DOI: 10.1097/HC9.0000000000000791
- Beyene HB, Wang T, Cinel M, et al. Lipidomic analyses of large cohort studies define the role of lipid metabolism in bridging diet and cardio-metabolic health. Nature Communications, 2026. DOI: 10.1038/s41467-026-71133-4
- NHLBI. Heart-healthy eating
Further reading
- Full-Fat Dairy and Cholesterol: What a New 12-Week Trial Found
- Glucose Spikes After Eating: What a New Heart Risk Study Found
- Prediabetes Diet and Liver Fat: What a New Trial Found
- Lipid Panel Explained: Cholesterol, LDL, HDL, and Triglycerides
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