A new survey, published in the British Journal of Nutrition, found that dietary supplements rival tea as the main source of total antioxidant capacity (TAC) in the US population, closely followed by fruit and fruit juices.
On the other hand, vegetables contribute almost nothing to the TAC, while coffee barely registered on the scale, report researchers from the University of Connecticut, Michigan State University and three universities in Korea.
The results were calculated from food and dietary supplement data from 4,391 US adults participating in the National Health and Nutrition Examination Survey (NHANES) 2001–2, and correlating this with US Department of Agriculture (USDA) flavonoid and proanthocyanidin databases.
“To our best knowledge, the present study is the first to document the baseline dietary TAC levels in the free-living US populations on a large scale. It provides a general insight of the real ‘quenching’ power of antioxidants and broadens our horizon to assess the antioxidant functions,” wrote the researchers in the British Journal of Nutrition.
“Importantly, on the journey of researching the dietary or physiological antioxidant status or their potential power for fighting against oxidative stress and therefore chronic diseases, considering antioxidants as a whole group, that is, as TAC, instead of individual nutrients, is a better direction,” they added.
The overall market for antioxidants was valued at $12bn (€8.8bn) in 2009, according to Euromonitor International, and applying a single measure for antioxidant activity may have a simplistic attraction for many. However, Professor Jeffrey Blumberg, Director of the Antioxidants Research Laboratory Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University told NutraIngredients-USA.com that TAC should only be considered as a concept.
“Only in a theoretical sense can vitamins C and E, flavonoids, carotenoids, proanthocyanidins, and other antioxidants all be expressed in a single value (i.e., vitamin C equivalents) as their actions in vivo are dependent upon their bioaccessibility, bioavailability, distribution, metabolism, elimination, and numerous molecular mechanisms of action,” said Prof Blumberg.
“Regarding this last point, TAC rates all nutrients/foods based on their antioxidant capacity in vitro which may or may not relate to their effects on inflammation or adiponectin, signal transduction, gene expression, etc.
“Thus, while this approach (with further research) may ultimately prove one index for investigating dietary assessments, it is unlikely to provide any explanation as to which dietary constituents are contributing via what specific mechanisms to any health or disease outcome,” he added.
In test tubes versus ‘in the body’
Commenting independently on the survey, Prof Blumberg noted that survey is one of several efforts by a few different research groups to find a way to assess very simply the dietary intake of a large and complex array of dietary constituents.
In an interview with NutraIngredients last year, Prof Blumberg explained that the term ‘antioxidant’ covers a range of “thousands of different compounds with wildly different chemical structures”. As such, there is the implication that all the compounds have the same mechanism of action. “It’s simplification that could get us into trouble,” he said.
According to Prof Blumberg, we need to move away from calling anything and everything an antioxidant.
“I’m not a lone voice, but I would like people to start thinking,” he said. “Stopping use of the term ‘antioxidant’ provides a terrific opportunity to differentiate yourself and promote the multifunctional benefits of these compounds we now call antioxidants.”
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114511000109
“Estimation of total antioxidant capacity from diet and supplements in US adults”
Authors: M. Yang, S-J. Chung, C.E. Chung, D-O. Kim, W.O. Song, S.I. Koo, O.K. Chun