British Journal of Nutrition

Human and Clinical Nutrition

Compliance, tolerability and safety of two antioxidant-rich diets: a randomised controlled trial in male smokers

Anette Karlsena1, Mette Svendsena2, Ingebjørg Seljeflota3, Mary-Ann Sommernesa2, Joseph Sextona4, Asgeir Brevika1, Iris Erlunda5, Mauro Serafinia6, Nasser Bastania1, Siv Fagertun Remberga7, Grethe I. Borgea8, Monica Hauger Carlsena1, Siv Kjølsrud Bøhna1, Mari C. Myhrstada1, Lars O. Dragsteda9, Asim K. Duttaroya1, Karin Haffnera7, Petter Laakea4, Christan A. Drevona1, Harald Arnesena3, Andrew Collinsa1, Serena Tonstada2 and Rune Blomhoffa1 c1

a1 Department of Nutrition, Faculty of Medicine, Institute of Basic Medical Sciences, University of Oslo, PO Box 1046, Blindern, 0316 Oslo, Norway

a2 Department of Preventive Cardiology, Oslo University Hospital Ulleval, Oslo, Norway

a3 Department of Cardiology, Center for Clinical Heart Research, Oslo University Hospital Ulleval, Oslo, Norway

a4 Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway

a5 Department of Chronic Disease Prevention, National Institute for Health and Welfare, Helsinki, Finland

a6 Unit of Human Nutrition, Antioxidant Research Laboratory, INRAN, Rome, Italy

a7 Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway

a8 Nofima Mat AS, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway

a9 Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark


It has been suggested that antioxidants attenuate oxidative stress and prevent oxidative stress-related diseases. Paradoxically, randomised controlled trials (RCT) using pharmacological doses of antioxidant supplements have demonstrated harmful effects in smokers. The aim of the present study was to test the compliance, tolerability and safety of two food-based antioxidant-rich diets in smokers. One of the diets provided antioxidants at levels similar to that used in RCT using supplements which previously have generated harmful effects. The present study followed a randomised, parallel-arm dietary intervention for 8 weeks (n 102) in male smokers (age ≥ 45 years). Participants were randomised to either antioxidant-rich diet, kiwi fruit or control groups. The antioxidant-rich foods provided about 300 mmol antioxidants/week from a wide range of plant-based food items. The kiwi fruit group consumed three kiwi fruits/d. Compliance to both diets was good. Only mild, undesirable events were reported by a minority of the participants. The safety of both diets was demonstrated as no potentially harmful or pro-oxidative effects were observed. In the antioxidant-rich diet group, the mean intake of antioxidants increased from 30 mmol/d at baseline to 62 mmol/d during the intervention. In conclusion, we have demonstrated that male smokers can comply with two food-based antioxidant-rich diets. Furthermore, the present study is the first to demonstrate the tolerability and safety of dietary antioxidants at levels similar to dosages provided in RCT using supplements. Such diets may be useful in future studies investigating whether dietary antioxidants may reduce oxidative stress and related diseases.

(Received April 27 2010)

(Revised December 15 2010)

(Accepted December 20 2010)

(Online publication May 12 2011)


c1 Corresponding author: R. Blomhoff, fax +47 22 85 13 41, email


†  Deceased.

Abbreviations: FRAP, ferric-reducing/antioxidant power; ORAC, oxygen radical absorbance capacity; RCT, randomised controlled trial