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Similar cholesterol–lowering properties of rice bran oil, with varied γ–oryzanol, in mildly hypercholesterolemic men*

Summary

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 γ–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) γ–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 γ–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 γ–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 γ–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.

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Abbreviations

ANOVA:

analysis of variance

BMI:

body mass index

C:

cholesterol

D:

day

HDL:

high density lipoprotein

HPLC:

high performance liquid chromatography

LDL:

low density lipoprotein

Lp(a):

Lipoprotein “little a”

n. d.:

not detectable

P1, P15 :

denotes the peanut oil period, experimental days 1 or 15

PNO:

peanut oil

R30, R43, R44, R45 :

denotes the rice bran oil period, experimental days 30, 43, 44, or 45

R43–45 :

denotes the rice bran oil period, average values for days 43–45

RBO:

rice bran oil

TAG:

triacylglycerol

TC:

total cholesterol

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Authors

Corresponding author

Correspondence to C. Bertoli.

Additional information

*This work appeared in part in FASEB J. 14: A250, 2000

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Berger, A., Rein, D., Schäfer, A. et al. Similar cholesterol–lowering properties of rice bran oil, with varied γ–oryzanol, in mildly hypercholesterolemic men*. Eur J Nutr 44, 163–173 (2005). https://doi.org/10.1007/s00394-004-0508-9

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Key words

  • cardiovascular risk
  • cholesterol
  • HDL
  • LDL
  • γ–oryzanol
  • peanut oil
  • rice bran oil