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Department of Public Health, University of Parma, Italy
Department of Internal Medicine and Biomedical Sciences, University of Parma, Italy
* To whom correspondence should be addressed. E-mail: nicoletta.pellegrini{at}unipr.it.
Dear Editor,
Dr. Chow and Dr. Chang raise doubts about the relevance of tools to estimate dietary total antioxidant capacity (TAC).
In their letter they express at least two points of concern, the first specifically related to our work and the second more generally related to the field of antioxidant research.
Regarding the first point, they state that the lack of association between intake of dietary TAC, measured by the semiquantitative FFQ, and plasma TAC represents a drawback of our work and "raises doubt about the value of the FFQ developed for assessing dietary TAC."
Our goal was to develop and validate a FFQ for the assessment of exposure to dietary TAC based on a large database of food TAC values measured by 3 different assays (1,2). In the validation of a FFQ, the first requirement is a reference method for evaluating food intake, and we used a 3-d weighed food record which, as acknowledged, "is indeed a more reliable method in measuring food intake than food daily or 24-h recall."
However, because the use of biochemical measurements of intake (i.e., biomarkers) is generally recommended to assess the biological plausibility of exposure (3) in the absence of a more meaningful biomarker of TAC intake, we decided to use plasma TAC. However, in complete agreement with Chow and Chang's view, we were perfectly aware that in vivo TAC would not have been a good indicator of consumption of antioxidant-rich diets. Therefore, in our opinion, this argument does not indicate a lack of reliability of our instrument in assessing exposure but simply reflects the lack of dietary modulation of plasma TAC likely due to a homeostatic mechanism by which endogenous antioxidants fluctuate to compensate for a reduced or enhanced presence of dietary antioxidants (4).
Concerning the second point, once agreed, that "although in vitro assays for dietary TAC may be useful in estimating antioxidant intake, they are not reliable in predicting antioxidant capacity in vivo, or even ex vivo," our perspectives seem to diverge. Chow and Chang suggest that "plasma TAC is generally regarded as an in vitro assay for in vivo function and is a more meaningful indicator of total antioxidant potential than in vitro or ex vivo assays for dietary TAC." We recently reported that dietary TAC was associated with lower systemic inflammation and to higher plasma concentrations of ß-carotene independently of ß-carotene intake (5,6). Again, epidemiological evidence also demonstrates an inverse relation between dietary TAC and gastric cancer (7), and even the high contribution of antioxidant-rich beverages (i.e., coffee and red wine) to dietary TAC does not belittle this dietary indicator. A large body of evidence supports the protective effect of coffee on the development of type 2 diabetes (8) and cancer (9) and of red wine on the risk of cardiovascular diseases (10).
We may agree that "a number of foods and beverages rich in phytochemicals have been associated with decreased risk of developing chronic diseases. However, whether the protective effect of these compounds is attributable to the antioxidant or other functions remains unclear." However, we repeat that this applies to other functional components of the diet as well, such as dietary fiber. Also, in this case, we face a multicomponent mixture of scarcely bioavailable molecules whose definition is based on a chemical analytical procedure, and for which a biological marker of exposure does not exist despite large epidemiological and experimental evidence of beneficial health effects. But the absence of a biological marker of exposure does not rule out the need to properly assess dietary intake of fiber, not to mention the implementation of recommendations to increase its level of intake in the general diet.
Sincerely,
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FOOTNOTES |
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2 Author disclosures: N. Pellegrini, D. Del Rio, F. Brighenti, and S. Valtueña, no conflicts of interest.
Manuscript received 22 March 2007.
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LITERATURE CITED |
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 TOP LITERATURE CITED |
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1. Pellegrini N, Serafini M, Colombi B, Del Rio D, Salvatore S, Bianchi M, Brighenti F. Total antioxidant capacity of plant foods, beverages, and oils consumed in Italy assessed by three different in vitro assays. J Nutr. 2003;133:2812–9.
2. Pellegrini N, Serafini M, Salvatore S, Del Rio D, Bianchi M, Brighenti F. Total antioxidant capacity of spices, dried fruits, nuts, pulses, cereals and sweets consumed in Italy assessed by three different in vitro assays. Mol Nutr Food Res. 2006;50:1030–8.[Medline]
3. Cade J, Thompson R, Burley V, Warm D. Development, validation and utilisation of food-frequency questionnaires - a review. Public Health Nutr. 2002;5:567–87.[Medline]
4. Serafini M, Del Rio D. Understanding the association between dietary antioxidants, redox status and disease: is the Total Antioxidant Capacity the right tool? Redox Rep. 2004;9:145–52.[Medline]
5. Brighenti F, Valtuena S, Pellegrini N, Ardigo D, Del Rio D, Salvatore S, Piatti P, Serafini M, Zavaroni I. Total antioxidant capacity of the diet is inversely and independently related to plasma concentration of high-sensitivity C-reactive protein in adult Italian subjects. Br J Nutr. 2005;93:619–25.[Medline]
6. Valtueña S, Del Rio D, Pellegrini N, Ardigò D, Franzini L, Salvatore S, Piatti PM, Riso P, Zavaroni I, Brighenti F. The total antioxidant capacity of the diet is an independent predictor of plasma ß-carotene. Eur J Clin Nutr. 2007;61:69–76.[Medline]
7. Serafini M, Bellocco R, Wolk A, Ekstrom AM. Total antioxidant potential of fruit and vegetables and risk of gastric cancer. Gastroenterology. 2002;123:985–91.[Medline]
8. van Dam RM, Hu FB. Coffee consumption and risk of type 2 diabetes: a systematic review. JAMA. 2005;294:97–104.
9. Tavani A, La Vecchia C. Coffee, decaffeinated coffee, tea and cancer of the colon and rectum: a review of epidemiological studies, 1990–2003. Cancer Causes Control. 2004;15:743–57.[Medline]
10. Naissides M, Mamo JC, James AP, Pal S. The effect of chronic consumption of red wine on cardiovascular disease risk factors in postmenopausal women. Atherosclerosis. 2006;185:438–45.[Medline]
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