Remembering everything you ate last week can be difficult, but your blood can retain its own traces: traces of how your body processed those meals.
Scientists have discovered that a blood signature linked to a Mediterranean-style diet is linked to the risk of dying years later. In a study of 14,584 people in Spain and the United States, groups with higher signature scores had a lower risk of death during follow-up.
The research, involving scientists from the University of Navarra, the Harvard TH Chan School of Public Health and other institutions, offers a way to study diet without relying solely on what people remember eating.
The Mediterranean-style diet emphasizes vegetables, fruits, legumes, nuts, fish and olive oil, while limiting red and processed meat. This pattern has been linked to various health benefits, but measuring how well a person follows it usually involves dietary questionnaires.
“Questionnaires depend on what people remember and report, so they are prone to misclassification,” Estefanía Toledo, an epidemiologist at the University of Navarra, told ScienceAlert.
When the body processes food, it produces or transforms small molecules called metabolites. These can contain information about what we eat and how our body reacts to it.
The researchers looked at a set of 67 metabolites, mostly lipids (fat-related molecules). Developed in 2020, the signature had already been associated with adherence to the Mediterranean diet and the risk of cardiovascular disease. The new study investigated its relationship with long-term mortality.
Many of these fats echo the staples of the diet. In previous work, some closely tracked olive oil consumption, while others tracked long-chain fatty acids found in nuts and fish.
The team started with blood samples collected from 1,880 participants after joining a Spanish dietary trial called PREDIMED. These were older people who did not have any cardiovascular disease at the time of enrollment but were at high risk of developing one.
Over approximately 13 years of follow-up, people in the top third of signature scores had a 23% lower risk of death than those in the bottom third, after taking into account factors such as age, smoking, body mass index and existing health conditions.
The researchers then examined data from 12,704 participants in three long-term American studies, followed for an average of 25 years.
The association reappeared: Participants in the highest quintile of signature scores had a 23 percent lower risk of death than those in the lowest quintile.
In the Spanish group, the association remained largely intact after accounting for self-reported adherence to the Mediterranean diet. Toledo explained that the signature may also reflect how each person’s body absorbs and handles food.
The authors suggest that a blood test like this could potentially help doctors identify people who have the most to gain by changing the way they eat.
The results cannot, however, tell someone how many years they have left.
“This indicates differences in risk between groups, not how long an individual lives,” Toledo said.
Although PREDIMED is a randomized dietary trial, this analysis of blood signature and mortality was observational, comparing people’s existing scores with what happened to them later. It cannot establish that increasing a person’s signature score would prolong their life.
Scores measured at the start of the trial and after one year, as well as their average, were associated with mortality, whereas signature changes during this first year of intervention were not.
The results suggest that the signature could reflect longer-term dietary habits and metabolic health, although it is unclear whether one year is too short to capture the effects of dietary changes.
Before this approach can become a routine blood test, it would need to be tested in more diverse populations, including people of different ages and health conditions.
The U.S. participants were medical professionals who were “mostly white and relatively healthy,” Toledo told ScienceAlert.
Researchers should also demonstrate that the signature improves risk prediction beyond established risk factors.
The research was published in The American Journal of Clinical Nutrition.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. Although we are proud of our process, we are only human. If you spot an error, please let us know.
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