Antioxidant Food Databases? Valuable or Not?Ronald L. Prior, Ph.D. ‡

Considerable debate and press has resulted from the recent removal by the USDA of the Oxygen Radical Antioxidant Capacity (ORAC) food database

from their website (1) http://www.ars.usda.gov/services/docs.htm?docid= 15866. One of the

reasons given for its removal was that “ORAC values are routinely misused by food and dietary supplement manufacturing companies to promote their products and by consumers to guide their food and dietary supplement choices.” It is unfortunate but true that numbers obtained from ORAC analysis have sometimes been misused, but that does not necessarily mean that the information is not useful if used appropriately. In too many cases, the goal has been to obtain the highest antioxidant value. It is not always the case that ‘more is better’ and in some cases using individual antioxidant compounds, more may be detrimental. A lot of misunderstanding results from lack of knowledge of free radical chemistry. Results with assays utilizing different oxidant or radical sources cannot produce exactly comparable data because the reaction mechanisms differ. It is interesting that at the time USDA removed the ORAC database, another was released for fruits in South America (2) (3):

http://portalantioxidantes.com/orac-base-de-datos-actividad-antioxidante-y-contenido-de-polifenoles-totales­en-frutas/

 

By implication, and from some of the statements that have been released, the question arises: “Is there value to having an ‘antioxidant capacity’ food database? Our science knowledge base as well as consumer acceptance and knowledge of antioxidants have changed considerably since the mid 1990s when some of the antioxidant capacity analytical tools came into being. The transition and advances have not been greatly different than for other food components in that, initially, the basic science and analytical tools were not available to measure all the individual components in a class of compounds, so more generic in vitro measures were used to assess their content in foods. In the mid 1990s there were several methods developed to assess “antioxidant capacity” or “antioxidant activity“.

Many of these methods used very different oxidants or radical sources. At that point in time, it was not really appreciated how important the radical source was. In the original ORAC method, the peroxyl radical was chosen for use in vitro because it represents one of the major radical sources present within the human body. Most of the other methods used radical sources that are totally foreign to the human body and thus provide information that is less relevant to human biology. Since that time, the basic ORAC method has been expanded so that the ability of food components to protect against four other primary radical sources (hydroxyl, superoxide, peroxynitrite, and singlet oxygen) can be evaluated. As we learned more about free radical actions, it became evident that the different radicals reacted with different antioxidant compounds differently and thus in most cases there was little or no correlation among the values obtained for the different radical sources used to assess antioxidant capacity. One example that stands out is tomato, which has a very low antioxidant capacity as measured with the peroxyl radical, but much higher antioxidant capacity using the singlet oxygen radical due largely to the carotenoid content of tomatoes and their ability to quench singlet oxygen.

 

All of the antioxidant assay methods are in vitro (‘test tube’) methods as are most of the other nutrient analyses of food ingredients and are subject to the disadvantages that are inherent in any in vitro method. ORAC using the peroxyl radical provides a measure of the antioxidant capacity primarily of a group of compounds called flavonoids. In the plant kingdom, there are several thousand individual flavonoid compounds. Although we have greatly improved analytical techniques for detecting and quantitating some of these compounds, we still do not have methods or standards to quantitate all of these compounds. ORAC has been an extremely useful analytical tool to compare the relative total quantities of these bioactive compounds plus other nonflavonoid compounds such as vitamins C and E. Does that mean that all of these compounds have antioxidant effects in vivo or act through an antioxidant mechanism? No. Does that mean that they all are efficiently absorbed into the body? No. Is the bioactive compound identical to the parent compound(s) found in the food? Possibly, but in many cases, probably not. Answers to these questions are the domain of in vivo investigation.

 

However, statements to the effect that “There is no evidence that the beneficial effects of polyphenol-rich foods can be attributed to the antioxidant properties of these foods” (1) are not consistent with the scientific evidence. A recent study (4) just released concluded that “Using the ORAC database, after adjusting for major covariates, we found decreased risks for the highest tertile of total phenolic intake compared with the lowest, … suggesting that total phenolic consumption may decrease endometrial cancer risk.” Another recent publication reported that: “Adherence to a Mediterranean-type diet, with emphasis on an increase in foods rich in antioxidants and close dietetic supervision, can increase total dietary antioxidant intake and plasma TAC in patients with abdominal obesity”(5). In fact, in the last 3 years there have been more than 25 publications dealing with dietary antioxidants (polyphenolics) and in vivo antioxidant status or disease (citations available upon request).

 

There is developing a considerable amount of scientific literature on the positive health benefits of the polyphenolic flavonoid-type compounds in foods. This is not to say that all of these effects are the result of only an antioxidant mechanism. However, oxidative stress is a major factor in most of the diseases of aging, even if it is not a causative factor. For example, oxidative stress and systemic inflammation are known to be involved in the pathogenesis of ischemic stroke and consuming a diet with a high total antioxidant capacity has been related to reduced inflammation along with increased circulating antioxidants (6). In a cross-sectional and randomized intervention study of 41,620 men and women, a diet rich in total antioxidant capacity was associated with a reduction in incidence of ischemic stroke and, to a lesser extent, in all types of stroke (6). In another study, positive associations were observed between dietary antioxidant capacity and adiponectin concentration and a negative relationship with inflammatory markers (7). An adiponectin-mediated route through which

antioxidant-rich foods exert beneficial effects against inflammation and cardiovascular diseases can be hypothesized (7).

 

There is continued growing interest in and questions regarding the antioxidant capacity of the diet and in vivo antioxidant status and effects on health outcomes. The antioxidant status during the postprandial state is important because a post-prandial pro-oxidant state may be a contributing factor to chronic disease, particularly following consumption of high fat and carbohydrate meals which can be pro-oxidant and as well as pro-inflammatory. A decrease in plasma antioxidant capacity has been observed following a meal containing macronutrients but no sources of antioxidants (8). The role of fruit and vegetable phenolic compounds to protect health and lower disease risk through their actions in mitigating fed-state metabolic and oxidative stressors is important. Berries such as blueberries, grapes, and strawberries have been shown to overcome the postprandial oxidative stress (8). More research is needed in this area, but data summarized from several studies (9) suggests that consuming phenolic-rich fruits increases the antioxidant capacity of the blood, and when they are consumed with high fat and carbohydrate 'pro-oxidant and pro-inflammatory' meals, they may counterbalance their negative effects.

 

So is there an ongoing value in using ORAC in nutrition? From my perspective, the answer is yes if used appropriately. What is meant by “appropriately”? Comparisons of data must be made using a standardized method using the same standard, units of expressing the data need to be clearly defined and comparisons between dried, partially dried, fresh foods, or juices or other processed food done with full recognition that the values cannot be directly compared. Monitoring changes in antioxidant capacity and using other analytical methods to follow individual compound changes during processing of foods is critical to assess and understand what the effects of processing are on the final product. Most important, ORAC should be used as a complementary analytical tool in the investigative process.

What are the future needs? Industry and science need to continue to develop more specific biomarkers of health and develop a better understanding of what happens to many of these bioactive flavonoid compounds during the digestion and absorption process. The expectation has never been that any one in vitro assay, regardless of its nature, would truly reflect everything that happens during this process. Without the ORAC database, we would not have had the opportunity to gather important epidemiology data that we now have relating antioxidant intake and various disease endpoints. Those involved in marketing are encouraged to use the data available in a reasonable way backed up with the best science that is available.

References:

1. USDA Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2. http://www.ars.usda.gov/services/docs.htm?docid=1 5866

2. Speisky, H.; Lopez-Alarcon, C.; Gomez, M.; Fuentes, J.; Sandoval-Acuna, C., First Web-Based Database on Total Phenolics and Oxygen Radical Absorbance

Capacity (ORAC) of Fruits Produced and Consumed within the South Andes Region of South America. Journal of Agriculture and Food Chemistry 2012, (Accepteed 4/19/2012).

1.  INTA ORAC: Database Antioxidant Activity and Total Polyphenol Content in Fruits (updated Feb 2012). http://portalantioxidantes.com/orac-base-de-datos­actividad-antioxidante-y-contenido-de-polifenoles-totales-en-frutas/

2.  Gifkins, D.; Olson, S. H.; Demissie, K.; Lu, S. E.; Kong, A. N.; Bandera, E. V., Total and individual antioxidant intake and endometrial cancer risk: results from a population-based case-control study in New Jersey. Cancer Causes Control 2012, 23, 887-95.

3.  Kolomvotsou, A. I.; Rallidis, L. S.; Mountzouris, K. C.; Lekakis, J.; Koutelidakis, A.; Efstathiou, S.; Nana-Anastasiou, M.; Zampelas, A., Adherence to Mediterranean diet and close dietetic supervision increase total dietary antioxidant intake and plasma antioxidant capacity in subjects with abdominal obesity. Eur J Nutr 2012, Epub date: 2012/01/13.

4.  Del Rio, D.; Agnoli, C.; Pellegrini, N.; Krogh, V.; Brighenti, F.; Mazzeo, T.; Masala, G.; Bendinelli, B.; Berrino, F.; Sieri, S.; Tumino, R.; Rollo, P. C.; Gallo, V.; Sacerdote, C.; Mattiello, A.; Chiodini, P.; Panico, S., Total antioxidant capacity of the diet is associated with lower risk of ischemic stroke in a large Italian cohort. J Nutr 2011, 141, 118-23.

5.  Detopoulou, P.; Panagiotakos, D. B.; Chrysohoou, C.; Fragopoulou, E.; Nomikos, T.; Antonopoulou, S.; Pitsavos, C.; Stefanadis, C., Dietary antioxidant capacity and concentration of adiponectin in apparently healthy adults: the ATTICA study. Eur J Clin Nutr 2009, 64, 161-8.

6.  Prior, R. L.; Gu, L.; Wu, X.; Jacob, R. A.; Sotoudeh, G.; Kader, A. A.; Cook, R. A., Plasma antioxidant capacity changes following a meal as a measure of the ability of a food to alter in vivo antioxidant status. J Am Coll Nutr 2007, 26, 170-181.

7. Burton-Freeman, B., Postprandial metabolic events and fruit-derived phenolics: a review of the science. Br J Nutr 2010, S 1-14.

‡ Consultant Nutritionist/Research Chemist, Adjunct Professor, Department of Food Science, University of AR. Contact: 214 Lakeshore Drive, Searcy, AR 72143; Email: rprior10@gmail.com; Phone: 501-743-8949