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Antioxidant intake, plasma antioxidants and oxidative stress in a randomized, controlled, parallel, Mediterranean dietary intervention study on patients with rheumatoid arthritis
Umeå University, Faculty of Social Sciences, Department of Food and Nutrition.
Umeå University, Faculty of Social Sciences, Department of Food and Nutrition.
Umeå University, Faculty of Social Sciences, Department of Food and Nutrition.
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2003 (English)In: Nutrition Journal, ISSN 1475-2891, E-ISSN 1475-2891, Vol. 2, no 5Article in journal (Refereed) Published
Abstract [en]

Background: Previously we have reported that patients with rheumatoid arthritis (RA) obtained a significant reduction in disease activity by adopting a Mediterranean-type diet. The present study was carried out to investigate the antioxidant intake, the plasma levels of antioxidants and a marker of oxidative stress (malondialdehyde) during the study presented earlier.

 Methods: RA patients randomized to either a Mediterranean type diet (MD group; n = 26) or a control diet (CD group; n = 25) were compared during a three month dietary intervention study. Their antioxidant intake was assessed by means of diet history interviews and their intake of antioxidant-rich foods by a self-administered questionnaire. The plasma levels of retinol, antioxidants (α- and γ-tocopherol, β-carotene, lycopene, vitamin C and uric acid) and urinary malondialdehyde (MDA), a marker for oxidative stress, were determined using high performance liquid chromatography. The Student's t-test for independent samples and paired samples were used to test differences between and within groups. For variables with skewed distributions Mann-Whitney U-test and Wilcoxon signed ranks test were performed. To evaluate associations between dietary intake of antioxidants, as well as between disease activity, MDA and antioxidants we used Pearson's product moment correlation or Spearman's rank correlation.

Results: The MD group had significantly higher intake frequencies of antioxidant-rich foods, and also higher intakes of vitamin C (p = 0.014), vitamin E (p = 0.007) and selenium (p = 0.004), and a lower intake of retinol (p = 0.049), compared to the CD group. However, the difference between the groups regarding vitamin C intake was not significant when under- and over-repoters were excluded (p = 0.066). There were no changes in urine MDA or in the plasma levels of antioxidants (after p-lipid adjustments of the tocopherol results), from baseline to the end of the study. The levels of retinol, vitamin C and uric acid were negatively correlated to disease activity variables. No correlation was found between antioxidant intake and the plasma levels of antioxidants.

Conclusions: Despite an increase in reported consumption of antioxidant-rich foods during the Mediterranean diet intervention, the levels of plasma antioxidants and urine MDA did not change. However, the plasma levels of vitamin C, retinol and uric acid were inversely correlated to variables related to RA disease activity.

Place, publisher, year, edition, pages
2003. Vol. 2, no 5
Research subject
Food and Nutrition
Identifiers
URN: urn:nbn:se:umu:diva-5396DOI: 10.1186/1475-2891-2-5OAI: oai:DiVA.org:umu-5396DiVA: diva2:144900
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-14
In thesis
1. A Mediterranean dietary intervention study of patients with rheumatoid arthritis
Open this publication in new window or tab >>A Mediterranean dietary intervention study of patients with rheumatoid arthritis
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Case control studies have shown that a high consumption of fish, olive oil, and cooked vegetables is associated with a decreased risk of developing rheumatoid arthritis (RA). These foods have a central position in the traditional Cretan Mediterranean diet, and it has been suggested that dietary factors contribute to the low prevalence of RA in Mediterranean countries. The overall aim of this thesis was to examine whether a modified Cretan Mediterranean diet can reduce signs and symptoms of RA. This was investigated in a three-month dietary intervention trial in which 51 patients with well controlled, although active RA of at least two years duration took part. A further aim was to study the compliance with the experimental and control diets used in the study, and to validate the diet history interview method used to assess the dietary intake. The validation was carried out by means of biological markers of dietary intake.

From baseline to the end of the study the group that had adopted the Cretan Mediterranean diet (MD group; n=26) obtained a reduction in disease activity, improved physical function, and improved vitality, while no changes was seen in the control diet group (CD group; n=25).

According to the dietary assessments, the intake frequencies of antioxidant-rich food items increased in the MD group. This group also had a significantly higher intake of vitamin E, vitamin C and selenium compared to the CD group. Despite the reported increase in the consumption frequencies of antioxidant-rich foods, the plasma levels of carotenoids, vitamin C, lipid adjusted tocopherols, uric acid and urine malondialdehyde, a marker of oxidative stress, were unchanged at the end of the study. The plasma levels of retinol, vitamin C and uric acid were, however, correlated to indices of disease activity. Changes in the reported consumption of food groups with relevance to the fat intake were also observed in the MD group, including an increased intake of fish, shellfish and poultry, and a decreased intake of meat and high fat dairy products. As a result, the total fat intake was lower in the MD group compared to the CD group. Furthermore, in the MD group a slightly higher percentage of the energy intake was derived from polyunsaturated fatty acids and a lower percentage from saturated fatty acids. This group also had a lower ratio of n-6:n-3 fatty acids. A corresponding change in the relation between n-6 and n-3 fatty acids was also observed in s-phospholipids.

The validation of the diet history interview method showed that the diet history interview could capture the dietary intake fairly well. The validity of the reported dietary intake did not differ between the MD and the CD group, which indicates that the dietary assessment was not biased by the dietary intervention.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2003. 93 p.
Keyword
Rheumatoid arthritis, Mediterranean diet, fatty acids, antioxidants, diet history interview, biological markers, doubly labelled water, energy expenditure
Identifiers
urn:nbn:se:umu:diva-89 (URN)91-7305-497-6 (ISBN)
Public defence
2003-09-26, Hörsal D, Samhällsvetarhuset, Umeå universitet, Umeå, 09:00 (English)
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Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2009-06-11Bibliographically approved

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