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Fruit and vegetable intake and the metabolic syndrome

Division of Human Nutrition
Wageningen University
PO Box 8129
Wageningen 6700 EV
Netherlands
E-mail: marianne.geleijnse{at}wur.nl

Dear Sir:

With great interest we read the article by Esmaillzadeh et al (1). The authors performed a cross-sectional study of fruit and vegetable intake in relation to the metabolic syndrome in 486 female Iranian teachers. The authors concluded that higher intakes of fruit and vegetables are associated with a lower risk of the metabolic syndrome. Because the prevalence of the metabolic syndrome ranged from 17% to 38% across the quintiles, it is not a rare disease. Esmaillzadeh et al used corrected prevalence odds ratios derived from logistic regression using a formula suggested by Zhang and Yu (2). This method, however, may yield inaccurate estimates and 95% CIs, especially when confounding is present. The preferred statistical method for a cross-sectional study with a common outcome is to obtain the prevalence ratio by log-binomial regression (3-5), eg, by means of PROC GENMOD in SAS (6).

ACKNOWLEDGMENTS

None of the authors declared a conflict of interest.

REFERENCES

1. Esmaillzadeh A, Kimiagar M, Mehrabi Y, Azadbakht L, Hu FB, Willett WC. Fruit and vegetable intakes, C-reactive protein, and the metabolic syndrome. Am J Clin Nutr 2006;84:1489–97.[Abstract/Free Full Text]
2. Zhang J, Yu KF. What's the relative risk? A method of correcting the odds ratio in cohort studies of common outcomes. JAMA 1998;280:1690–1.
3. Skov T, Deddens J, Petersen MR, Endahl L. Prevalence proportion ratios: estimation and hypothesis testing. Int J Epidemiol 1998;27:91–5.[Abstract/Free Full Text]
4. Robbins AS, Chao SY, Fonseca VP. What's the relative risk? A method to directly estimate risk ratios in cohort studies of common outcomes. Ann Epidemiol 2002;12:452–4.[Medline]
5. Thompson ML, Myers JE, Kriebel D. Prevalence odds ratio or prevalence ratio in the analysis of cross sectional data: what is to be done? Occup Environ Med 1998;55:272–7.[Abstract]
6. Spiegelman D, Hertzmark E. Easy SAS calculations for risk or prevalence ratios and differences. Am J Epidemiol 2005;162:199–200.[Free Full Text]

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sluik, D. Articles by Geleijnse, J. M Search for Related Content PubMed PubMed Citation Articles by Sluik, D. Articles by Geleijnse, J. M Agricola Articles by Sluik, D. Articles by Geleijnse, J. M