Medical Perspectives | Integrative Med, Others

July 30, 2021

Doctor Ma.Haidee L. Ibañez MD

Antioxidant nutrition is not only a fad today but an obsession for some individuals. Most health nuts are fixated on the latest trends of health options available in the market. A lot of people jump on the bandwagon without knowing the theories behind these products. Some people are eager to consume anything that has “healthy”, “organic”, or “antioxidant” on its label. For consumers to fully maximize the health benefits from food, it is a must to know the concepts behind antioxidant nutrition.

What are antioxidants?

Antioxidants are substances that remove potentially damaging oxidizing agents. Reactive oxygen species(ROS) are unstable molecules that are produced during normal cell metabolism such as cellular respiration and interaction of biomolecules with ionizing radiation.  They can strip electrons from other molecules thereby causing chain reaction of oxidative damage which in turn would result to degenerative changes of aging and most age-related diseases. There are several mechanisms that could reduce or convert the ROS species into harmless byproducts. These include actions of antioxidant enzymes, proteins, and antioxidants provided by nutrition.

Antioxidants could delay cell damages caused by free radicals eventually leading to disease prevention.Antioxidants can be found in fruits, herbs, spices, and vegetables. Intake of antioxidants has tons of benefits which includes improved skin, eye, and heart health.  The free-radical theory of ageing and disease states that a high antioxidant intake from foods will slow the oxidative processes and free radical damage that contributes to age-related degeneration and disease. Because of the health benefits from antioxidants there has been a great interest in accurately determining the antioxidant capability of food, cosmetics, dietary supplements, and pharmaceutical agents. Some experts in antioxidant nutrition would often base their intake on a food’s oxygen radical absorbance capacity (ORAC) values.

What is an ORAC?

ORAC is an analytical laboratory test that determines the in vitro “total antioxidant capacity” (TAC) of a certain food.  It was originally developed by the National Institute on Aging (NIA) at the National Institute of Health (NIH). There are plenty of laboratory tests to determine the TAC of a certain food but so far, ORAC has been frequently used. ORAC is commonly used because it is low cost.

Measuring ORAC is popular because it measures the TAC of the entire food. Other laboratory tests use specific and individual nutrients such as vitamin E.  Plants may contain certain exceptional antioxidants that have not yet been discovered hence, measuring it individually will be impossible. ORAC therefore could measure the synergistic effects between the various nutrients in a specific food. There have been studies that have proven that some nutrients could be more effective in combination than they are independently.

How is an ORAC measured?

A food sample is placed on a test tube with different molecules that could generate free radical activity and could also oxidize the food sample. The sample would then be set aside for a while to allow the oxidizing agents to interact with the antioxidants. The ability of the food sample to protect the vulnerable molecules from oxidation by the free radicals will be measured.

ORAC relies on a common fluorescent probe called flourescein. It is used to monitor the antioxidant activity which can be read on a microplate reader which is capable of detecting fluorescence.  The oxidizing reagent would result in a loss of fluorescent intensity over time. The TAC of the food sample will be high if there is less free radical damage. Higher ORAC values indicate a higher measured amount of in vitro antioxidant activity.

How many ORAC units do you need?

Dr. Ronald Prior, a researcher of the US Department of Agriculture (USDA) Research said that a significant increase in antioxidants in the body of about 15-20% could be possible by consuming foods that are high in ORAC values. Most scientists and researchers who have focused on ORAC and antioxidants studies have cited that the body can effectively use 3,000-5,000 ORAC units per day. An excess would be of no use since the antioxidant capacity of the blood is tightly regulated. The extra would be simply excreted by the kidneys.

There is no “official” daily recommended consumption of ORAC units. Various publications have suggested an optimal intake of 3,000-5,000 ORAC units per day, while the USDA has a suggested intake of 5,000 ORAC units per day.  On the other hand, the United Kingdom Food Standards Agency (UK FSA) and the Food and Drug Administration (FDA)recommends 5 servings of fruits and vegetables which is equivalent to 3,500 0RAC units.

Which food has high ORAC values?

Fruits,vegetables, herbs, and spices are the common sources of antioxidants. A list of the ORAC levels of almost all types of food could easily be searched online. There are no certain values for a specific food because the ORAC values of a fruit, vegetable, spice, or herb are not only dependent on species, but also highly dependent on geographical origin and harvest time (Ou, 2002). Therefore, lettuce grown in Baguio could have a greater or lesser ORAC value than lettuce grown elsewhere. ORAC levels found online could serve as a guide but they do not really indicate the exact values.

In a list by the website superfoodly, dragon’s blood (red tree sap) from the croton lechleritree found in South America had the highest ORAC level at 2,897,110 μ mol TE/100gfollowed by astaxanthin (a derivative of the microalgae Hematococcuspluvis), and triphala powder which is a combination of herbs from India used in Ayurvedic medicine.

A study by Ehlendfeldt (2001) has indicated that natural grown food could have a greater ORAC values than those grown commercially. The study suggests that some gene combinations contributing to the ORAC values may be broken up by hybridization and by the chemicals being added such as fertilizers and insecticides. Organic food has been proven to contain higher ORAC levels than commercially grown products because they have lesser interaction with compounds that may affect the TAC of a certain food product.


Ehlenfeldt MK and Prior RL.Oxygen Radical Absorbance Capacity (ORAC) and Phenolic and Anthocyanin Concentrations in Fruit and Leaf Tissues of Highbush Blueberry. April 27,2001.Journal of Agricultural and Food Chemistry. Vol 49:, Issue.5,:Pages. 2222-2227.

OuB., Huang D, Hampsch-Woodill, Flanagan JA, and DeemerEK .(April 27,2002). Analysis of Antioxidant Activites of Common Vegetables Employing Oxygen Radical Absorbance Capacity (ORAC) and Ferric Reducing antioxidant Power (FRAP) Assays: A Comparative Study. Journal of Agricultural and Food Chemistry. Vol. 50:, Issue. 11,: Pages 3122-3128  (July 9,2018) (July 9,2018) (July 9, 2018) 


Read more about

Was this article helpful? Rate us!

Suggested For You

Comprehensive Overview: Efficacy, Tolerability, and Cost-effectiveness of Irbesartan

Fotini Gialama and Nikos Maniadakis

3 min read

integrative med


3 min read


10 pieces of advice for new physicians

1 min read


Be The first to know