麻豆传媒

SACRAMENTO, Calif., Oct. 12 -- Plant sterols added to orange juice can significantly reduce markers of cardiovascular risk, researchers here reported.

One gram of plant sterols added into reduced-calorie orange juice reduced C-reactive protein by 12% (P<0.005) and significantly improved cholesterol levels compared with plain low-calorie OJ, reported Sridevi Devaraj, Ph.D., of the University of California at Davis here, and colleagues, in the October issue of the American Journal of Clinical Nutrition.

Downing the supplemented juice twice daily significantly decreased total cholesterol by 5% (P<0.01) and reduced LDL cholesterol by 9.4% (P<0.001) compared with study participants' baseline levels and compared to placebo.

Likewise, HDL levels improved significantly compared with baseline (6% increase, P<0.02), though not with placebo, over the eight-week period.

While some previous studies have seen a drop in fat-soluble vitamins with plant sterol supplementation, the investigators noted no significant change in vitamin E and carotenoid concentrations.

"Dietary therapy is the cornerstone of strategies aimed at reducing LDL cholesterol and thereby reducing the risk of [cardiovascular disease]," wrote Dr. Devaraj and colleagues. Incorporating foods fortified with plant sterols in the daily diet offers an "attractive strategy" to reach the 2 g of plant sterols recommended by the National Cholesterol Education Program's Adult Treatment Panel III, they added.

Plant sterols can be found in small quantities in foods, such as fruits, vegetables, nuts, seeds, cereals and legumes, and have been added to some margarines and other spreads. They are chemically similar to cholesterol but presumably suppress absorption of cholesterol in the intestines and promote cholesterol's exit from the body.

The double-blind trial included 72 healthy volunteers ages 19 to 74 (mean 44 sterol group, 48 placebo group). After an overnight fast, blood samples were drawn for baseline measurements and then half the participants were randomized to each arm of the study, Those in each arm consumed about eight ounces (240 mL) of juice with breakfast and dinner. They were asked not to eat margarine or other spreads containing plant sterols in the month before and during the study.

The plant sterols in the beverage were derived from vegetable oils and comprised mainly of beta-sitosterol, campesterol, and stigmasterol. All participants had a normal complete blood count, LDL cholesterol higher than 100 mg/dL, normal liver and renal function, and no secondary causes of hypercholesterolemia or use of medications or supplements that would affect cholesterol or C-reactive protein levels. Baseline lipid profiles were similar between groups.

The researchers found that total cholesterol:

• Fell from 213 mg/dL at baseline in the sterol group to 209 mg/dL at four weeks and 208 mg/dL at eight weeks, but

• Increased slightly from 217 mg/dL at baseline and four weeks in the placebo group to 218 mg/dL at eight weeks.

LDL cholesterol levels were similarly affected:

They decreased from 144 mg/dL at baseline in the sterol group to 145 mg/dL at four weeks and then 139 mg/dL at eight weeks, but stayed about the same, from 145 mg/dL at baseline in the placebo group to 143 mg/dL at week four and 145 mg/dL at week eight.

C-reactive protein levels fell significantly by 12% (P<0.02).

The researchers reported no significant correlation between reductions in LDL-cholesterol and C-reactive protein concentrations (P>0.05).

HDL cholesterol improved in both groups, but significantly more so in the sterol group. They went from 45 mg/dL at baseline in the sterol group to 46 mg/dL at four weeks and 48 mg/dL at eight week. In the placebo group they went from 46 mg/dL at baseline in to 48 mg/dL at four weeks and 47 mg/dL at eight weeks.

The concern with plant sterol supplementation is that it may not only reduce LDL concentrations by inhibiting cholesterol absorption but may also reduce other lipophilic compounds such as carotenoids and vitamin E at the same time.

Although, apolipoprotein B concentrations fell from 106 mg/dL to 96 mg/dL during the study in the sterol group, there were no significant changes in apolipoprotein A1 concentrations. Neither were there significant changes in triacylglycerol, glucose, or liver function tests in the sterol group.

The study was supported by Coca-Cola, the Beverage Institute for Health & Wellness, and a grant to one of the investigators by the National Institutes of Health. The lower-calorie orange juice was supplied by Coca-Cola, which has a patent pending.

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