No other cyanobacterium (blue-green algae) is as popular for nutrition as Arthrospira platensis. What is the ORAC value of spirulina? How much antioxidant activity does it have? Getting to the bottom of this question is no easy task.
As is the case with many superfoods, once an ORAC value is referenced for it by someone (i.e. dietary supplement company), it turns into a game of telephone. Another company will state the ORAC of the food is X, because they saw the first company claim that. This continues and before long, you have a plethora of online sources stating a given value, without any of them even knowing where it came from!
It gets worse when that unconfirmed value starts to get cited in academic papers, as is the case with spirulina. Buried deep within the 125 page graduate thesis paper published on the University of South Florida Scholar Commons website, the author states the ORAC of spirulina is 61,900 umol on page 96 (1). The paragraph which cites this number is not footnoted. The paragraph before cites a footnote, but the topic discussed in it is not related to ORAC. The paragraph after does not cite a footnote, but that doesn't matter since it is also an unrelated topic (it's about spirulina increasing the levels of CX3CR1, which is a chemokine called fractalkine).
Since this paper appears to provide zero sourcing for this 61,900 value, we can only conclude they cherry picked it from one of the websites or blogs during that time period. Going deeper, it appears those blogs referenced it from one of several dietary supplement companies who were using that number in their marketing material (again, with zero sourcing for it).
Is 61,900 the real ORAC?
ORAC testing is not cheap. It's a complex series of tests and given that its a patented process, very few laboratories are even licensed to conduct it. Rather than pay several thousand for their own testing, it is not surprising that some companies take a shortcut and merely regurgitate the number they find online for the nutrient.
Brunswick Laboratories, ORAC's creator, is the most well known tester. Searches for terms like this yield no reports online: spirulina orac brunswick. No reports are found or referenced on a .edu or .gov website whatsoever. This would be unusual given that the NIH publishes an entry and abstract for virtually all legitimate scientific studies related to health. If there were one related to spirulina and the study included an ORAC value, we would expect to find it in our extensive searches of the NIH database.
Conclusion? We believe the 61,900 figure is false.
Whether it was an intentional deception by the original nutritional company who cited it, or merely an innocent mistake by them, we do not know. That being said, evidence suggests it may be the latter - an innocent mistake - of converting mmol to umol.
ORAC test results are typically published in mmol, but the published values which are most commonly used for consumers are in umol. During the time period the USDA published ORAC values, they reported them in umol. We too publish in umol.
To convert mmol to umol, you multiply by 1,000.
Despite the fact that it is not published online, it is by no means outside the realm of possibility that a test was performed sometime in past relating to the 61,900 figure. In other words, the root source of that number may very well be legitimate and not fabricated. We believe, based on the below evidence, that the original value for pure spirulina powder was 6.19 mmol and a miscalculation was done in the conversion of that to umol. Rather than multiplying by 1,000, they multiplied by 10,000... leading to the 61,900 value which is so often cited online.
The strongest evidence supporting this
In 2010, a very extensive report of ORAC values was published in Nutrition Journal (see source below). This study was very thorough and had very respected names behind it. Not many exotic superfoods were tested. Primarily, the report looked at common whole foods (e.g. vegetables, fruits, meats) and many processed foods, such as Aunt Jemima pancakes and 7-Eleven brownies. There were some test results for less common foods and nutrients, one of which was for GNC 500 mg spirulina capsules/pills.
The ORAC for the spirulina capsules came in at 5,970.
A "0" size gel capsule holds exactly 500 mg of a powdered nutrient. Given that it was labeled as containing 500 mg of spirulina, with reasonable confidence we can conclude fillers were not present. Of course the capsule itself though is an inert ingredient, or something other than spirulina.
The ingredients of the capsule GNC used in this product (at least in 2016) are as follows: Gelatin, Cellulose, Dicalcium Phosphate.
Gelatin itself does not contain antioxidants and therefore, the capsule shell would only decrease the ORAC rather than increase it.
Based on the weight ratio of the capsule shell versus the powder inside, it would be reasonable to conclude that if one were testing only the powder inside, the ORAC would be 3 to 4% higher... 6,190.
The ORAC value of pure spirulina is around 6,000.
Figures citing a multiple of 10x that number are virtually impossible, regardless of the source of spirulina or the processing techniques used.
Even with a species of plants which vary somewhat dramatically, such as conventional cultivated blueberries and wild blueberries, the maximum difference seen in ORAC is around 2x (the wild being 2x higher), and that is for different species of the fruit.
With the genus spirulina, it is true there are dozens of species (as is the case with blueberries) but it is highly unlikely that any two would vary by a factor of 10x. In fact for dietary supplements, virtually all today use Arthrospira platensis, which is superior to distant 2nd place food source used, Arthrospira maxima (found off the coasts of California and Mexico, used albeit quite rarely). Based on patterns seen elsewhere in the plant kingdom, the maximum difference we would expect would be 4x between species and even that would be extremely rare. Considering that research has concluded Arthrospira platensis to be the gold standard and being that virtually all nutritional companies use it, we should expect only negligible differences in ORAC values between products.
Research Support, Non-U.S. Gov't: Carlsen MH, Halvorsen BL, Holte K, et al. Nutrition Journal NIH Jan 2010