FRAP Antioxidant Ranking

FRAP (Ferric Reducing Antioxidant Power) measures a food's total capacity to donate electrons and reduce oxidised molecules. It's a fast, reproducible assay that reflects the combined reducing power of all antioxidants in a food extract — polyphenols, vitamin C, vitamin E, carotenoids, and others. Unlike ORAC (which measures radical absorbance) or DPPH assays, FRAP specifically tests reduction capacity at low pH, making it particularly sensitive to flavonoids and phenolic acids.

Yes, significantly. Boiling leaches water-soluble polyphenols into cooking liquid, which can reduce FRAP values by 20–50%. Roasting and baking can cause some polyphenol degradation but also concentrate antioxidants as moisture is lost. Steaming retains more antioxidant activity than boiling. The values in this database represent raw or standard-preparation values — actual FRAP after cooking will vary depending on method, time, and temperature.

Not directly — and the gap between test-tube scores and real-body activity can be dramatic. Dr. Michael Greger at NutritionFacts.org highlights a striking example: spinach ranks #1 in standard chemical antioxidant assays like FRAP and ORAC, yet when researchers measured actual cellular antioxidant activity — how antioxidants protect living cells — spinach didn't even make the top ten. Beets, by contrast, rank #1 in cellular antioxidant activity despite a more modest FRAP score. FRAP measures how foods slow down a specific chemical reaction in a test tube, a reaction that doesn't occur in living cells. Bioavailability — how much is actually absorbed, how gut bacteria transform it, and whether it reaches target tissues — determines real-world impact far more than any lab score. Use FRAP as a useful guide to polyphenol richness, but don't use it to compare foods head-to-head for health value.

FRAP values are expressed in µmol Fe²⁺ equivalents per 100g (micromoles of ferrous iron equivalent per 100 grams of food). This reflects how many micromoles of ferric iron (Fe³⁺) the food's antioxidants can reduce to ferrous iron (Fe²⁺) under standard conditions. Some studies express FRAP per serving or per 100 mL for liquids. When comparing values across databases, always check the unit — mmol/100g (millimoles) means the same number would be 1,000× higher than µmol/100g.

FRAP values strongly correlate with total polyphenol content because polyphenols are the dominant reducing compounds in plant foods. However, not all polyphenols have the same FRAP contribution — some flavonoids are stronger reducing agents than others, and non-polyphenol antioxidants like vitamin C also add to FRAP scores. For the most comprehensive view of a food's polyphenol profile, the Phenol-Explorer polyphenol database provides compound-by-compound breakdowns.

Yes — unlike ORAC, which was discontinued by the USDA in 2012, FRAP remains widely used in both food science and clinical nutrition research. It is valued for its simplicity, speed, and reproducibility. The comprehensive FRAP database used here, compiled by researchers at the University of Oslo, covers over 1,000 plant based foods and continues to be cited in peer-reviewed studies on dietary antioxidant intake and health outcomes.