Phytosterols that are naturally present in commercial corn oil significantly reduce cholesterol absorption in humans

Am J Clin Nutr. 2002 Jun;75(6):1000-4. doi: 10.1093/ajcn/75.6.1000.


Background: Although supplementing the diet with large quantities of phytosterols reduces cholesterol absorption and LDL-cholesterol concentrations, very little is known about the smaller amounts of phytosterols present naturally in food. Vegetable oils are the richest dietary source of phytosterols; corn oil contains 0.77% phytosterols by weight.

Objective: We tested the hypothesis that removing phytosterols from corn oil would increase cholesterol absorption when measured in single-meal tests containing corn oil as a source of fat.

Design: Free and esterified phytosterols were removed from corn oil on a kilogram scale by a new technique of competitive saturation adsorption to silica. Healthy subjects with a mean (+/-SEM) serum cholesterol concentration of 5.10 +/- 0.18 mmol/L received an otherwise sterol-free test breakfast on 2 occasions 2 wk apart that contained 35 mg hexadeuterated cholesterol and 30-35 g of a corn oil preparation. The plasma enrichment of tracer was measured by negative ion mass spectrometry.

Results: Cholesterol absorption was 38.0 +/- 10.2% higher after consumption of the sterol-free corn oil than after consumption of commercial corn oil with an identical fatty acid content (P = 0.005; n = 10). When corn oil phytosterols were added back to sterol-free corn oil at a concentration of 150 mg/test meal, cholesterol absorption was reduced by 12.1 +/- 3.7% (P = 0.03; n = 5) and by 27.9 +/- 9.1% (P = 0.01; n = 10) after inclusion of 300 mg phytosterols.

Conclusions: Phytosterols comprising < 1% of commercial corn oil substantially reduced cholesterol absorption and may account for part of the cholesterol-lowering activity of corn oil previously attributed solely to unsaturated fatty acids.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Absorption
  • Adult
  • Cholesterol / blood
  • Cholesterol / pharmacokinetics*
  • Cholesterol, LDL / blood
  • Cholesterol, LDL / metabolism
  • Corn Oil / analysis
  • Corn Oil / chemistry*
  • Cross-Over Studies
  • Deuterium
  • Double-Blind Method
  • Female
  • Humans
  • Hypercholesterolemia / blood
  • Hypercholesterolemia / prevention & control*
  • Male
  • Mass Spectrometry
  • Phytosterols / pharmacology*
  • Phytosterols / therapeutic use


  • Cholesterol, LDL
  • Phytosterols
  • Corn Oil
  • Cholesterol
  • Deuterium