A Systematic Screening of Total Antioxidants in Dietary Plants1
Bente L. Halvorsen,* Kari Holte,* Mari C. W. Myhrstad,* Ingrid Barikmo,** Erlend Hvattum,† Siv Fagertun Remberg,† Anne-Brit Wold,† Karin Haffner,† Halvard Baugerød,† Lene Frost Andersen,* Jan Ø. Moskaug,* David R. Jacobs, Jr.‡ and Rune Blomhoff*2
*Institute for Nutrition Research, Faculty of Medicine,University of Oslo, Blindern, 0316 Oslo, Norway; **Akershus University College, Bekkestua, Norway; †Agricultural University of Norway, Ås, Norway; and the ‡ Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis, MN 55454
ABSTRACT A predominantly plant-based diet reduces the risk for development of several chronic diseases. It is often assumed that antioxidantscontribute to this protection, but results from intervention trials with single antioxidants administered as supplements quite consistently do not support any beneﬁt. Because dietary plants contain several hundred different antioxidants, it would be useful to know the total concentration of electrondonating antioxidants (i.e., reductants) in individual items. Such data might be useful in the identiﬁcationof the most beneﬁcial dietary plants. We have assessed systematically total antioxidants in a variety of dietary plants used worldwide, including various fruits, berries, vegetables, cereals, nuts and pulses. When possible, we analyzed three or more samples of dietary plants from three different geographic regions in the world. Total antioxidants was assessed by the reduction of Fe3 to Fe2 (i.e.,the FRAP assay), which occurred rapidly with all reductants with half-reaction reduction potentials above that of Fe3 /Fe2 . The values, therefore, expressed the corresponding concentration of electron-donating antioxidants. Our results demonstrated that there is more than a 1000-fold difference among total antioxidants in various dietary plants. Plants that contain most antioxidants includedmembers of several families, such as Rosaceae (dog rose, sour cherry, blackberry, strawberry, raspberry), Empetraceae (crowberry), Ericaceae (blueberry), Grossulariaceae (black currant), Juglandaceae (walnut), Asteraceae (sunﬂower seed), Punicaceae (pomegranate) and Zingiberaceae (ginger). In a Norwegian diet, fruits, berries and cereals contributed 43.6%, 27.1% and 11.7%, respectively, of the totalintake of plant antioxidants. Vegetables contributed only 8.9%. The systematic analysis presented here will facilitate research into the nutritional role of the combined effect of antioxidants in dietary plants. J. Nutr. 132: 461– 471, 2002. KEY WORDS:
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A general consensus has been reached during the last few years that diet has a major role in the development of chronic diseases, such as cancer, coronary heart disease, obesity, diabetes type 2, hypertension and cataract (1–9). This consensus suggests that a predominantly plant-based diet rich in fruits and vegetables, pulses and minimally processed starchy staple foods reducesthe risk for development of these diseases signiﬁcantly. The recommendations, which are mainly based on epidemiological studies are thus, that fruits, vegetables and less processed staple foods provide the best protection against the development of disease with little or no merit in recommending vitamin or other micronutrient supplements for disease prevention (1–9). This is a safe principle thatpromises to provide for improved public health. However, these general recommendations avoid the issue of which dietary plants to eat. A large and remaining challenge, therefore, is to identify the most beneﬁcial dietary plants. Furthermore, a complete
1 This work was supported by the Norwegian Cancer Society, the Research Council of Norway, the Novo Nordic Foundation, Eckboes Foundation and the...