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Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals

European Journal of Clinical Nutrition volume 65, page 421 (2011)Cite this article

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In the March 2010 issue of EJCN, Torabian et al. (2010) reported the effects of walnut consumption on serum lipids, specifically, total serum cholesterol and low-density lipoprotein (LDL) cholesterol. This randomized crossover trial included 87 subjects who were assigned to a walnut-supplemented group or control group for 6 months and then crossed over to the alternate diet for 6 months.

Although the findings are generally consistent with the results from previous studies (Banel and Hu, 2009), it seems as though this trial could be strengthened with refined analysis and interpretation of the data collected. For instance, the authors only controlled for body weight that resulted in significant changes of total cholesterol and LDL levels. However, it seems necessary to also present the results with and without control for total energy intake, in addition to the adjustment for body weight. The average total energy consumption for participants on the walnut-supplemented diet and the control diet was 8171 and 7614 kJ, respectively (Torabian et al., 2010). The mean difference between daily total energy intake (557 kJ) during the two diet periods is approximately 50% less than the actual energy intake from walnuts (967 kJ). As the authors stated, a substitution effect cannot be excluded. In other words, it is very likely that the observed effects of walnut consumption on serum lipids in this trial are explained by a mixed substitution effect and an addition effect of walnut consumption. To simulate the potential substitution effects in the statistical model, energy adjustments are needed (Willett et al., 1997). Therefore, it may be very helpful in understanding the true effects of walnut supplementation on the lipid profile if the authors can present their results both with and without adjustment for total energy intake.

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References

  • Banel DK, Hu FB (2009). Effects of walnut consumption on blood lipids and other cardiovascular risk factors: a meta-analysis and systematic review. Am J Clin Nutr 90, 56–63.

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  • Torabian S, Haddad E, Cordero-MacIntyre Z, Tanzman J, Fernandez ML, Sabate J (2010). Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals. Eur J Clin Nutr 63, 274–279.

    Article  Google Scholar 

  • Willett WC, Howe GR, Kushi LH (1997). Adjustment for total energy intake in epidemiologic studies. Am J Clin Nutr 65 (Suppl), 1220S–1228S.

    Article  CAS  Google Scholar 

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Authors and Affiliations

  1. Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    C Y Um

  2. Department of Nutrition and Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    K He

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  1. C Y Um
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  2. K He
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Correspondence to C Y Um.

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Um, C., He, K. Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals. Eur J Clin Nutr 65, 421 (2011). https://doi.org/10.1038/ejcn.2010.246

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