Blood Carotenoid Levels May Accurately Reflect Fruit and Vegetable Consumption Patterns: Study

What if doctors could tell how healthy your diet is just by testing your blood, urine, or even your skin? Scientists are getting closer to that reality with a growing field of research focused on "dietary biomarkers" - measurable chemicals in the body that may reveal how many fruits and vegetables a person actually eats.

A new review published in Nutrition Bulletin examined the most promising biomarkers currently being studied to objectively measure fruit and vegetable intake.

Traditional methods such as food diaries, 24-hour recalls, and food frequency questionnaires rely heavily on memory and honesty. That can make it difficult for researchers to accurately connect diet with long-term health outcomes like heart disease, obesity, diabetes, and cancer.

Scientists are now investigating biological markers that change in response to fruit and vegetable consumption. Among the strongest candidates are vitamin C, carotenoids, folate, flavonoids, hippuric acid, and potassium.

Blood carotenoids currently appear to be the most reliable biomarker overall. These natural plant pigments are found in colorful produce such as carrots, spinach, tomatoes, and peppers. Since the human body cannot make carotenoids on its own, higher blood levels generally reflect higher fruit and vegetable intake.

Researchers are also exploring skin carotenoid scans as a faster, noninvasive alternative to blood testing. Meanwhile, serum vitamin C may help measure recent fruit and vegetable consumption, especially in people who do not regularly take supplements.

Urinary flavonoids and hippuric acid also show promise because they reflect compounds naturally abundant in plant foods. However, these markers can also be influenced by tea, coffee, wine, chocolate, and spices, making interpretation more complicated.

The review highlights that no single biomarker is perfect. Factors like age, medications, smoking, alcohol use, supplements, genetics, and underlying health conditions can all influence results.

REFERENCE: Madore MP. 2026. A Narrative Review of Candidate Biomarkers of Total Fruit and Vegetable Intake. Nutrition Bulletin. https://onlinelibrary.wiley.com/doi/10.1111/nbu.70054