The effects of phytosterols present in natural food matrices on cholesterol metabolism and LDL-cholesterol: a controlled feeding trial

Abstract

Background/objectives: Extrinsic phytosterols supplemented to the diet reduce intestinal cholesterol absorption and plasma low-density lipoprotein (LDL)-cholesterol. However, little is known about their effects on cholesterol metabolism when given in native, unpurified form and in amounts achievable in the diet. The objective of this investigation was to test the hypothesis that intrinsic phytosterols present in unmodified foods alter whole-body cholesterol metabolism.

Subjects/methods: In all, 20 out of 24 subjects completed a randomized, crossover feeding trial wherein all meals were provided by a metabolic kitchen. Each subject consumed two diets for 4 weeks each. The diets differed in phytosterol content (phytosterol-poor diet, 126 mg phytosterols/2000 kcal; phytosterol-abundant diet, 449 mg phytosterols/2000 kcal), but were otherwise matched for nutrient content. Cholesterol absorption and excretion were determined by gas chromatography/mass spectrometry after oral administration of stable isotopic tracers.

Results: The phytosterol-abundant diet resulted in lower cholesterol absorption (54.2±2.2% (95% confidence interval 50.5%, 57.9%) vs 73.2±1.3% (69.5%, 76.9%), P<0.0001) and 79% higher fecal cholesterol excretion (1322±112 (1083.2, 1483.3) vs 739±97 mg/day (530.1, 930.2), P<0.0001) relative to the phytosterol-poor diet. Plasma lathosterol/cholesterol ratio rose by 82% (from 0.71±0.11 (0.41, 0.96) to 1.29±0.14 μg/mg (0.98, 1.53), P<0.0001). LDL-cholesterol was similar between diets.

Conclusions: Intrinsic phytosterols at levels present in a healthy diet are biologically active and have large effects on whole-body cholesterol metabolism not reflected in circulating LDL. More work is needed to assess the effects of phytosterol-mediated fecal cholesterol excretion on coronary heart disease risk in humans.

Figures

Figure 1. Individual percent cholesterol absorption (A) and LDL-cholesterol (B) in response to two levels of phytosterol intake from natural foods

Cholesterol absorption and LDL-cholesterol were determined as described in Materials and Methods. Individual values are presented for 20 subjects who received 2 levels of phytosterol intake (126 or 449 mg phytosterols per 2000 kcal) for 4 weeks each in a crossover design.

Figure 2. Fecal cholesterol excretion (dietary and endogenous) in response to 2 levels of phytosterol intake from natural foods

Excretion of dietary (hatched bars) and endogenous (white bars) cholesterol was measured as described in Materials and Methods in 20 subjects in a two-treatment (phytosterol-poor: 126 mg/2000 kcal and phytosterol-abundant diet: 449 mg/2000 kcal)/two-period crossover study. Each phytosterol intake period lasted for 4 weeks. The level of statistical significance is indicated by **P