Scientifically, Oxygen Radical Absorbance Capacity (ORAC) is the laboratory standard in measuring antioxidant levels in foods. The ORAC test was developed at the National Institute on Aging (NIA) in the US, the leader in aging research.
ORAC in a nutshell
- ORAC measures the ability of a food to neutralize oxidizing free radicals, per 100g, in a test tube.
- It is an easy and standardized tool to compare the inherent antioxidant capacity of different foods
- The higher the score, the more antioxidant capacity the food contains.
Seem fair and objective, isn’t it? Well, there are some caveats when interpreting the ORAC scores.
Are we comparing apple to apple?
To make sense of ORAC values, it is important to consider the food type, i.e. fresh, dried, freeze-dried. One should not compare the ORAC of fresh blueberry with the ORAC of dried cranberry, for instance.
This is because when fruits are dried, two scenarios may occur:
- Depending on the type of antioxidants they contain, they may lose the antioxidants (i.e. become oxidized) during the drying process, and the resultant ORAC score will be lower than the fresh version.
- If the antioxidant content is unaffected, they become more concentrated for the same 100g weight when dried (since the water weight is gone) and so the ORAC value will be higher than the fresh fruit itself.
For objective comparison, we have selected the ORAC scores of fresh produce when making the ORAC chart above.
Does higher ORAC score translate into higher antioxidant activity in our body?
This is a very valid question. Higher ORAC score determined from the test tube may not mean higher antioxidant activity in our body.
It is, however, possible to investigate how food affects our antioxidant status by measuring the antioxidant capacity (AOC) in our blood. One study conducted by the researchers at the USDA checked the AOC level of volunteers after consuming blueberries, cherries, dried plums, and other high antioxidant fruits. Interestingly, they found that…
- dried plums, despite their high antioxidant content, did not raise blood AOC levels in volunteers.
- in the case of blueberries, they did not detect a noticeable increase in AOC until volunteers consumed at least a half-cup serving of the berries.
And how much antioxidants3 are degraded or lost when cooking/heating our food before we even eat it?
Of all antioxidants4, vitamin C is probably the least heat stable, and being water soluble, is easily lost in solution. One study found that boiling broccoli for just 5 minutes reduced the vitamin C content in broccoli by 45 to 64%!
This is because the vitamin is first leached out of the broccoli into the water, and then degraded by the heat. Therefore, for food rich in vitamin C like broccoli, it is better to steam than boil, to avoid vitamin C leaking into the water. But steaming will still cause vitamin C to be degraded in the heat. Best if you can eat it raw.
On the other side of the spectrum, anthocyanins, the purple pigment phytonutrient which is also a powerful antioxidant, was found in a study by NUS to retain the antioxidant activity in temperatures up to 165°C and under various pH levels tested, from 2.2 to 6.0.
Anthocyanins are found in varying levels in fruits, grains and vegetables with the color of purple, blue and red, such as Peruvian purple corn, açaí berries, black currants, blackberries, black rice, purple sweet potatoes, raspberries, and blueberries.
So, which antioxidants5 should I choose?
There are actually various health benefits beyond the antioxidant capacity that most antioxidants6 have on our body. Of the five main types of antioxidants7, each have different and important functions in our body. This will be discussed in subsequent posts. Sign up for our email updates to stay tuned!
6 thoughts on “Antioxidants – beyond the ORAC scores”
Specifically for dried fruit such as cranberries, how do you know if the cried cranberries will have a food ORAC, if there are 2 possible scenarios. Is this a lab test that needs to be performed on a product to determine?
Thanks for your question. ORAC is an in vitro (lab test) done on food on their capacity to absorb oxygen radicals (i.e. antioxidant capacity). USDA has released a list of foods tested including fresh and dried food. It is now not available on USDA site but you can download it here http://www.orac-info-portal.de/download/ORAC_R2.pdf (see page 10 onwards). There has been comments that because ORAC is done in vitro, it might not represent the in vivo response when consumed into our body. However, it is still a good indication to see which food naturally contains more antioxidants than the others. Hope this clarifies 🙂
Thank you Amber, for your reply. Actually that was the website I had gone to initially, however I did go back and check again and sadly to say, dried cranberries, blueberries and some other fruits are not listed. If perhaps you know of another website that does have this information please let me know.
Thanks for your reply. Apologies, our article above did not refer to dried cranberries specifically, but fresh blueberries and dried plums based on this study https://www.tandfonline.com/doi/full/10.1080/07315724.2007.10719599. Hope this clarifies.
When avocados turn brown they are oxidizing so can we assume that the ORAC score would decrease?
And would it be substantial? It seems only to oxidize where exposed directly to the air so maybe even if it does decrease ORAC it might not be substantial??? What are your thoughts.
Hi Sandra, thank you for your question. Yes, the enzymatic oxidation (browning) of fruits when exposed to air will cause some of its nutrients to be degraded by the oxidation process. It also indicates that the fruit doesn’t have enough antioxidant to counteract/prevent the enzymatic oxidation. If you look at fruits with antioxidants such as kiwi, lemon and oranges (all 3 contain Vit C) – they don’t get brown after being cut open or sliced.
How substantial would the ORAC score be reduced – we can’t really answer that without testing the browned avocado for its ORAC score. However, avocado doesn’t have a high ORAC score to begin with, 1922 vs apple 3049 μmol TE/100 g.