Similar cholesterol-lowering properties of rice bran oil, with varied gamma-oryzanol, in mildly hypercholesterolemic men.

BACKGROUND: The cholesterol lowering properties of rice bran oil (RBO) containing differing amounts of non-saponifiable components have not been studied in humans, to our knowledge. AIM OF THE STUDY: To evaluate cholesterol lowering effects of RBO, with low and high amounts of gamma-oryzanol (ferulated plant sterols) in mildly hypercholesterolemic men. METHODS: Mildly hypercholesterolemic men, 38-64 y, starting cholesterol 4.9-8.4 mmol/l (n = 30), consumed 50 g/d peanut oil (PNO) in vehicles for 2 wks during a run-in period, then, without wash-out, were randomly equilibrated (based on initial level of cholesterol) into two groups to consume 50 g/d RBO low (0.05 g/d) or high (0.8 g/d) gamma-oryzanol for 4 wks, in a randomized, controlled, parallel design study. Subjects were free-living and consumed habitual diets with some restrictions. Plasma concentrations of total, LDL-,HDL-cholesterol and triacylglycerol were measured at base line and after 2, 4, and 6 wks. RESULTS: The two RBO types were not significantly different with respect to effects on various cholesterol parameters, at 2 and 4 wks, including total cholesterol, LDL-, HDL- and LDL/HDL cholesterol ratio. Low and high gamma-oryzanolcontaining RBO feeding for 4 wks lowered total plasma cholesterol (6.3 %), LDL-C (10.5 %) and the LDL-C/HDL-C ratio (18.9 %). CONCLUSIONS: RBO supplementation at ca. 50% total fat intake improved lipoprotein pattern in mildly hypercholesterolemic men. Methylated sterols in gamma-oryzanol are thought to be largely ineffective at inhibiting dietary cholesterol absorption, but could enhance cholesterol-lowering ability of 4-desmethylsterols. Assuming all ferulated sterols become de-ferulated in the gut, low and high gamma-oryzanolcontaining RBOs provided intestinal loads of 453 and 740 mg/d free 4-desmethylsterols, respectively. This intestinal load of 453-740 mg/d of efficacious free plant sterol equivalents had identical effects on lipoproteins.

Matching avrami indices achieves similar hardnesses in palm oil-based fats.

This study demonstrates how chemically interesterified hydrogenated palm oil (IHPO) and partially hydrogenated palm oil (PHPO) can be structured to have similar mechanical properties. Crystallization of IHPO at 30 degrees C for 24 h yielded a fat with a solid fat content (SFC) of 45% and a yield force of 51.5 N. On the other hand, PHPO had a SFC of 50% and a yield force of 44 N when crystallized under the same conditions. The result was opposite from what would be expected from the SFC point of view, thus suggesting that the microstructure of the fat plays a key role in determining mechanical properties. By matching crystallization behavior using the Avrami index as a guide, microstructures and material hardness were successfully matched. These results suggest that the dynamics of structure formation was a key factor influencing the macroscopic mechanical properties of palm oil-based fats.

Dietary trans-18:1 raises plasma triglycerides and VLDL cholesterol when replacing either 16:0 or 18:0 in gerbils.

To compare the relative impact of trans-18:1 with the two main dietary saturated fatty acids it replaces, plasma lipid response was assessed in Mongolian gerbils fed diets rich in 16:0 (24%en),18:0 (10%en), or trans-18:1 (4 or 6%en). The diets were designed such that the 18:0-rich diet substituted 7%en as 18:0 for 16:0, whereas 4%en and 6%en from trans-18:1 was substituted for 16:0 in the two trans diets. The control group was fed a diet formulated according to the fatty acid balance of American Heart Association (AHA), but provided 40%en as fat. Gerbils (n = 10 per dietary group) were fed one of the five diets for 8 weeks. The control diet, with 4 times the polyunsaturated fatty acids (PUFA) content and a P:S ratio about 10 times greater than the test diets, resulted in the lowest plasma TC, LDL cholesterol (LDL-C) and VLDL cholesterol (VLDL-C). Among the test diets, plasma TC and TG were lowest with the 18:0-rich diet. TC in gerbils fed the 16:0-rich diet and 4%en-trans were 20% higher than the 18:0-rich diet, while the 6%en-trans diet was 35% higher. VLDL-C was significantly higher in the 6%en-trans diet compared to all other groups at 8 weeks. Both trans fatty acid diets elevated plasma TG approximately 2- and 3-fold, respectively, compared to the 16:0-rich and 18:0-rich diets at 8 weeks. Further, plasma TG continued to rise over time with trans fatty acids compared to 16:0 or 18:0. Thus, in the fatty acid-sensitive gerbil, impaired TG metabolism represents a major aspect of the hyperlipemia caused by trans fatty acid substitution for major saturated fatty acids.

Formation of modified fatty acids and oxyphytosterols during refining of low erucic acid rapeseed oil.

Formation of trans fatty acids and cyclic fatty acid monomers was investigated during refining of low erucic acid rapeseed oil. The first steps of the refining process, that is, degumming, neutralization, and bleaching, hardly modified the fatty acid profile. In contrast, deodorization produced substantial quantities of trans fatty acids (>5% of total fatty acids) and small amounts of cyclic fatty acid monomers (650 mg of cyclic fatty acid monomers/kg of oil) when severe conditions (5-6 h at 250 degrees C) were used. Alpha-linolenic acid was the main precursor of cyclic fatty acid monomers. The influence of deodorization on the chemical composition of low erucic acid rapeseed oil was studied additionally. Whereas free fatty acids, peroxides, and tocopherols decreased, neither total polar compounds nor oxyphytosterols changed during deodorization. Oxyphytosterols were identified by GC-MS. Three oxyphytosterols not yet observed in oil were tentatively identified as 6beta-hydroxycampestanol, 6beta-hydroxysitostanol, and 6beta-hydroxybrassicastanol. Brassicasterol oxides were the most abundant oxyphytosterols.