Phytosterols Clinical Evidence

Asia Pacific Journal of Clinical Nutrition
Wu T et al. The effects of phytosterols/stanols on blood lipid profiles: a systematic review with meta-analysis. 2009; 18(2):179–86.

Topic:
Are phytosterols/stanols effective at lowering cholesterol?

Background:
Phytosterols and stanols are cholesterol-like molecules found in plants. They are thought to lower cholesterol levels, possibly by competing with cholesterol for absorption.

Study Type:
Review paper

Summary:
Researchers screened 76 studies and found 20 of sufficiently high methodological quality to consider.  Analyzing the data from these trials, they found phytosterols/stanols can significantly decrease LDL (bad) cholesterol and triglycerides.

Conclusions:
“Foods enriched with 2.0 g of phytosterols/stanols per day had a significant cholesterol-lowering effect.”

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Journal of the American College of Nutrition
Zhao HL et al. Action of plant sterol intervention on sterol kinetics in hypercholesterolemic men with high versus low basal circulatory plant sterol concentrations. 2011 Apr; 30(2):155–65.

Topic:
How does supplementation with plant sterols (PS) affect subjects with high and low levels of PS at base line?

Background:
The relationship between PS absorption and cholesterol absorption and synthesis is not well understood.

Study Type:
Human clinical intervention trial

Study Design:
Subjects consumed a spread enriched with PS or one without PS. Their levels of campesterol and beta-sitosterol (two kinds of PS) as well as their cholesterol concentrations and rates of cholesterol synthesis were measured.

Dosage:
2 g/day for two 4-week periods, separated by a 4-week washout period

Subjects:
82 men with high cholesterol

Results:
Consumption of PS-enriched products reduced cholesterol by 34.3% ± 1.9%, although cholesterol synthesis also increased in this group. The cholesterol-lowering effect of PS was strongest among subjects who were in the 50th–75th percentile of PS concentrations at base line.

Conclusions:
“These data suggest that basal PS concentrations indicate not only sterol absorption efficiency but also the extent of PS-induced cholesterol reduction and thus might be clinically useful to predict the extent of cholesterol response to PS intervention within a given individual.”

The American Journal of Clinical Nutrition
Devaraj S, BC Autret, I Jiala. Reduced-calorie orange juice beverage with plant sterols lowers C-reactive protein concentrations and improves the lipid profile in human volunteers. 2006 Oct; 84(4):756–61.

Topic:
What is the effect of supplementing with plant sterols (PS) on C-reactive protein (CRP) and cholesterol levels?

Background:
Plant sterols have been shown to reduce LDL cholesterol. Can they also reduce inflammation, which is a factor in atherosclerosis (hardening of the arteries)?

Study Type:
Human clinical intervention trial

Study Design:
Randomized, placebo-controlled. Subjects drank beverages with or without PS. Fasting blood samples were taken at base line and at 8 weeks.

Dosage:
1 g/twice daily for 8 weeks

Subjects:
72 healthy subjects

Results:
Supplementing with PS significantly reduced total cholesterol and LDL cholesterol. There was also a significant reduction in levels of CRP, a marker of inflammation. There were no significant changes in triglycerides, glucose, liver function, or levels of vitamin E and carotenoids (plant pigments the body can convert to vitamin A).

Conclusions:
“Supplementing with a reduced-calorie orange juice beverage containing plant sterols is effective in reducing CRP and LDL cholesterol and could be incorporated into the dietary portion of therapeutic lifestyle changes.”

European Journal of Clinical Nutrition
Korpela, R., et al. Safety aspects and cholesterol-lowering efficacy of low fat dairy products containing plant sterols. 2006 May; 60(5):633–42.

Topic:
What is the effect of supplementing with plant sterols (PS) on cholesterol levels and on levels of fat-soluble vitamins?

Background:
Some vitamins are transported and stored in water-based body fluids and others in fat. If plant sterols successfully lower cholesterol levels, might levels of fat-soluble vitamins also decrease?

Study Type:
Human clinical intervention trial

Study Design:
Parallel, double-blind. Subjects consumed PS-enriched low-fat dairy products. Researchers measured their levels of cholesterol and fat-soluble vitamins.

Dosage:
2 g/day for 6 weeks

Subjects:
164 subjects with mildly to moderately elevated cholesterol

Results:
Subjects consuming the PS-enriched dairy products saw their PS blood levels rise and experienced a 6.5% reduction in their total cholesterol levels, while there was no change in the control group. In addition, LDL (bad) cholesterol fell by 10.4% in the sterol group and by only 0.6% in the control group. There was no change in either group in HDL (good) cholesterol or triglycerides, but because the LDL levels fell among members of the treatment group, their HDL/LDL ratio rose by 16.3%, while in the control group, this ratio rose by only 4.3%. Levels of fat-soluble vitamins did not decrease when total levels of cholesterol were considered.

Conclusions:
“Yogurt, low-fat hard cheese and low-fat fresh cheese enriched with a plant sterol mixture reduced serum cholesterol in hypercholesterolemic subjects and no adverse effects were noted in the dietary control of hypercholesterolemia.”

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European Journal of Clinical Nutrition
Thomsen AB et al. Effect of free plant sterols in low-fat milk on serum lipid profile in hypercholesterolemic subjects. 2004 Jun; 58(6):860–70.

Topic:
What is the effect of supplementing with plant sterols (PS) on subjects with mildly elevated cholesterol? What is the optimal dose?

Background:
Plant sterols are thought to reduce levels of LDL (bad) cholesterol. Is this treatment effective?

Study Type:
Human clinical intervention trial

Study Design:
Double-blind, randomized, placebo-controlled, three-arm crossover study. Subjects all took a placebo, a low dose of PS, and a higher dose of PS in different phases of the study. Researchers measured their LDL cholesterol levels.

Dosage:
1.2 g or 1.6 g/day for 4 weeks each

Subjects:
138 subjects with mildly elevated cholesterol screened, 81 participated, 71 completed

Results:
In the low-dose group, LDL cholesterol was lowered by an average of 7.13 ± 12.32%, and in the high-dose group by 9.59 ± 12.44%. The difference between the two doses was not statistically significant. There were no significant changes in vitamin E or carotenoid levels after supplementation.

Conclusions:
“The present study shows for the first time a substantial reduction in LDL cholesterol with a new, partly vegetable-oil-filled 1.2% low-fat milk product, containing nonesterified (unsaturated) plant sterols from soybean oil, in a randomized, placebo-controlled trial. This result encourages further development of novel low-fat dairy products containing free plant sterols for future use in cholesterol-lowering initiatives.”

European Journal of Nutrition
Christiansen LI et al. Cholesterol-lowering effect of spreads enriched with microcrystalline plant sterols in hypercholesterolemic subjects. 2001 Apr; 40(2):66–73.

 Topic:
How does a new, microcrystallized form of plant sterols (PS) perform in lowering cholesterol?

Background:
Previous research has shown PS can lower cholesterol levels.  The effectiveness of the sterols depends on their form, however.

Study Type:
Human clinical intervention trial

Study Design:
Double-blind, randomized, placebo-controlled. Subjects consumed a rapeseed oil–based spread for 6 weeks before the PS was introduced. Then the subjects were divided into 3 groups, a control group that continued to consume the rapeseed oil spread, a group that consumed a low dose of PS, and one that consumed a higher dose. There were no other dietary or lifestyle changes. Researchers then measured their total and LDL (bad) and HDL (good) cholesterol levels.

Dosage:
1.5 g or 3 g/day for 6 weeks

Subjects:
155 subjects with high cholesterol

Results:
Total cholesterol levels and LDL cholesterol levels were significantly decreased by 7.5%–11.6% in the treatment group. The effect was similar in the low- and high-dose groups. There was no change in HDL cholesterol or triglycerides and no negative side effects.  Levels of fat-soluble vitamins did not decrease.

Conclusions:
“Microcrystalline plant sterols are effective in lowering serum total- and LDL-cholesterol concentrations without obvious side effects. The daily dose of 1.5 g plant sterols is enough to reach the maximum effect.”

 Mechanism of Action

Plant sterols inhibit the uptake of cholesterol, possibly by decreasing the solubility of cholesterol and by displacing it from the sites that absorb it. Sterols activate liver X receptor, which regulates cholesterol, and increase the expression of ATP-binding cassette G transporters (ABCG), proteins that transport substances across cellular membranes. ABCG then redirects absorbed PS back into the intestines