Open Access Research

The effect of walnut intake on factors related to prostate and vascular health in older men

Kim J Spaccarotella1, Penny M Kris-Etherton2, William L Stone3, Deborah M Bagshaw2, Valerie K Fishell2, Sheila G West4, Frank R Lawrence5 and Terryl J Hartman2*

Author affiliations

1 Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ 08901, USA

2 Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA 16802, USA

3 Department of Pediatrics, East Tennessee State University, Johnson City, TN 37614, USA

4 Department of Biobehavioral Health, The Pennsylvania State University, University Park, PA 16802, USA

5 Department of Human Development and Family Studies, The Pennsylvania State University, University Park, PA 16802, USA

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Citation and License

Nutrition Journal 2008, 7:13  doi:10.1186/1475-2891-7-13

Published: 2 May 2008

Abstract

Background

Tocopherols may protect against prostate cancer and cardiovascular disease (CVD).

Methods

We assessed the effect of walnuts, which are rich in tocopherols, on markers of prostate and vascular health in men at risk for prostate cancer. We conducted an 8-week walnut supplement study to examine effects of walnuts on serum tocopherols and prostate specific antigen (PSA). Subjects (n = 21) consumed (in random order) their usual diet +/- a walnut supplement (75 g/d) that was isocalorically incorporated in their habitual diets. Prior to the supplement study, 5 fasted subjects participated in an acute timecourse experiment and had blood taken at baseline and 1, 2, 4, and 8 h after consuming walnuts (75 g).

Results

During the timecourse experiment, triglycerides peaked at 4 h, and gamma-tocopherol (γ-T) increased from 4 to 8 h. Triglyceride – normalized γ-T was two-fold higher (P = 0.01) after 8 versus 4 h. In the supplement study, change from baseline was +0.83 ± 0.52 μmol/L for γ-T, -2.65 ± 1.30 μmol/L for alpha-tocopherol (α-T) and -3.49 ± 1.99 for the tocopherol ratio (α-T: γ-T). A linear mixed model showed that, although PSA did not change, the ratio of free PSA:total PSA increased and approached significance (P = 0.07). The α-T: γ-T ratio decreased significantly (P = 0.01), partly reflecting an increase in serum γ-T, which approached significance (P = 0.08).

Conclusion

The significant decrease in the α-T: γ-T ratio with an increase in serum γ-T and a trend towards an increase in the ratio of free PSA:total PSA following the 8-week supplement study suggest that walnuts may improve biomarkers of prostate and vascular status.