Effects of dietary phytosterols on inflammation and lipid peroxidation in vivo
School of Chemical & Life Sciences

Background: Plant sterols have been known to lower the blood cholesterol concentrations in hypercholesterolemic subjects.  There is limited in vivo human data regarding the simultaneous measurement of effects after acute and prolonged exposure to plant sterols-enriched food product on blood lipid profile, inflammation and oxidative status in healthy individuals. Limited data is available on the effects of plant sterols intervention on myeloperoxidase and 5-lipoxygenase activity in vivo.

Objective: A randomized, double-blinded, placebo-controlled and crossover study was conducted to examine the effects after acute and 4-week dietary plant sterol consumption on the blood lipid profile, inflammation and oxidative status in 18 healthy individuals.

Methods: The participants received 2 soy milk (20g) treatments daily: placebo and one containing 2.0g free plant sterols equivalent of their palmityl esters (β-sitosterol, 55%; campesterol, 29% and stigmasterol, 23%). F2-isoprostanes, leukotriene B4, sitosterol, campesterol and stigmasterol concentrations were measured in the blood plasma and urine, using stable isotope-labelled gas chromatography - mass spectrometry. High sensitivity c-reactive protein,  tumor necrosis factor-α and lipoxin A4 concentrations in blood serum were measures using commercially available enzyme immunoassays.

Results: Myeloperoxidase activity, serum lipid hydroperoxides, plasma and urinary F2-isoprostanes, plasma and urinary leukotriene B4, and plasma high-sensitivity c-reactive protein concentrations were significantly reduced, while circulating lipoxin A4 concentrations were significantly elevated after 4-week plant sterols treatment. Plant sterols treatment decreased plasma leukotriene B4 and increased plasma lipoxin A4 concentrations acutely. Circulating concentrations of total plant sterols, β-sitosterol, campesterol and stigmasterol increased were significantly elevated after 4-week treatments compared to the pre-treatment concentrations.

Conclusions: Our results suggest that dietary plant sterols, in the combination used, can alleviate lipid peroxidation and inflammatory events in vivo. These effects are possibly exerted via the modulation of myeloperoxidase and 5-lipoxygenase activity.