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 (gamma-T) increased from 4 to 8 h. Triglyceride – normalized gamma-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 micromol/L for gamma-T, -2.65 +/- 1.30 micromol/L for alpha-tocopherol (alpha-T) and -3.49 +/- 1.99 for the tocopherol ratio (alpha-T: gamma-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 alpha-T: gamma-T ratio decreased significantly (P = 0.01), partly reflecting an increase in serum gamma-T, which approached significance (P = 0.08).
Conclusions
The significant decrease in the alpha-T: gamma-T ratio with an increase in serum gamma-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.