Dietary Plant Sterols Supplementation Increases In Vivo Nitrite and Nitrate Production in Healthy Adults: A Randomized, Controlled Study

Abstract

A randomized, double-blinded, placebo-controlled and crossover study was conducted to simultaneously measure the effects, 3 h after consumption and after 4-wk daily exposure to plant sterols-enriched food product, on in vivo nitrite and nitrate production in healthy adults. Eighteen healthy participants (67% female, 35.3 [mean] ± 9.5 [SD] years, mean body mass index 22.8 kg/m2 ) received 2 soy milk (20 g) treatments daily: placebo and one containing 2.0 g free plant sterols equivalent of their palmityl esters (β-sitosterol, 55%; campesterol, 29%; and stigmasterol, 23%). Nitrite and nitrate concentrations were measured in the blood plasma and urine, using stable isotope-labeled gas chromatography-mass spectrometry. L-arginine and asymmetric dimethylarginine concentrations in blood serum were measured using commercially available enzyme immunoassays. Nitrite and nitrate concentrations in blood plasma (nitrite 5.83 ± 0.50 vs. 4.52 ± 0.27; nitrate 15.78 ± 0.96 vs. 13.43 ± 0.81 μmol/L) and urine (nitrite 1.12 ± 0.22 vs. 0.92 ± 0.36, nitrate 12.23 ± 1.15 vs. 9.71 ± 2.04 μmol/L) were significantly elevated after 4-wk plant sterols supplementation Placebo and 3-h treatments did not affect the blood plasma and urinary concentrations of nitrite and nitrate. Circulating levels of L-arginine and asymmetric dimethylarginine were unchanged in the placebo and treatment arms. Total plant sterols, β-Sitosterol, campesterol, and stigmasterol concentrations were significantly elevated after 4-wk treatments compared to the placebo and 3-h treatments. Blood plasma nitrite and nitrate concentrations correlated significantly with the plasma total and specific plant sterol concentrations. Our results suggest that dietary plant sterols, in the combination used, can upregulate nitrite, and nitrate production in vivo.

Keywords: L-arginine; nitrate; nitric oxide; nitrite; plant sterols.

© 2017 Institute of Food Technologists®.

Figures

Figure 1

(A) Nitrite and (B) nitrate concentrations in blood plasma of 18 healthy adults before (baseline), 3 h after intervention (3 h) and after 4‐wk daily exposure (4 wk) of the placebo and plant sterols esters (2 g free plant sterols equivalent)‐enriched soy milk. *,P < 0.05 compared with placebo soy milk after baseline adjustment (mixed model analysis with Tukey's test).

Figure 2

(A) Nitrite and (B) nitrate concentrations in the urine of 18 healthy adults before (baseline), 3 h after intervention (3 h) and after 4‐wk daily exposure (4 wk) of the placebo and plant sterols esters (2 g free plant sterols equivalent)‐enriched soy milk. *,P < 0.05 compared placebo soy milk after baseline adjustment (mixed model analysis with Tukey's test).

Figure 3

(A) Arginine and (B) asymmetric dimethylarginine concentrations in blood plasma of 18 healthy adults before (baseline), 3 h after intervention (3 h) and after 4‐wk daily exposure (4 wk) of the placebo and plant sterols esters (2 g free plant sterols equivalent)‐enriched soy milk. *,P < 0.05 compared placebo soy milk after baseline adjustment (mixed model analysis with Tukey's test).

Figure 4

Changes (%) in (A) nitrite and (B) nitrate formation by phorbol 12‐myristat 13‐acetate‐stimulated human blood neutrophils treated with β‐sitosterol (●), campesterol (■), stigmasterol (▲) and plant sterols mixture (50% β‐sitosterol, 30% campesterol, 20% stigmasterol w/w, ▼; 0 to 50 μmol/L) compared to the untreated phorbol 12‐myristat 13‐acetate‐stimulated human blood neutrophils. *,P < 0.05 compared with others using ANOVA of AUC with Bonferroni post hoc adjustment.