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


METHODS
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.
Ostlund
Richard E
RE
Division of Endocrinology, Diabetes and Metabolism, Washington University, St Louis, MO 63110, USA. rostlund@imgate.wustl.edu
Racette
Susan B
SB
Okeke
Alfred
A
Stenson
William F
WF
D000042:Absorption; D000328:Adult; D002784:Cholesterol / Q000097:blood / Q000493:pharmacokinetics*; D008078:Cholesterol, LDL / Q000097:blood / Q000378:metabolism; D003314:Corn Oil / Q000032:analysis / Q000737:chemistry*; D018592:Cross-Over Studies; D003903:Deuterium; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000517:prevention & control*; D008297:Male; D013058:Mass Spectrometry; D010840:Phytosterols / Q000494:pharmacology* / Q000627:therapeutic use
D008078:Cholesterol, LDL; D010840:Phytosterols; D003314:Corn Oil; D002784:Cholesterol; D003903:Deuterium