Plant sterols are structurally similar to cholesterol
and are often called phytosterols. Stanols are saturated sterols and have no double bond in the ring structure.
More than forty sterols have been identified from plants, of which beta-sitosterol, campesterol and stigmasterol are the most abundant. Beta-sitosterol comprises 50% of dietary plant sterols.
The average daily intake of phytosterol from the diet
is approximately 250 mg/day, while that of stanol is approximately 25 mg/day.
Plant sterols and stanols may be esterified to modify solubility in water and oil.
While approximately 50% of dietary cholesterol is absorbed, only about 0.5% of plant sterols and 0.05% of plant stanols are absorbed.1
The Food and Drug Administration has approved health claims on plant sterol and stanol products. The possible claim is that phytosterols may maintain healthy cholesterol with a low fat diet.2,3
In 2002, the Adult Treatment Panel III (ATP III) of the National Cholesterol Education Program (NCEP) published the Final Report on the Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Plant sterols and stanols (2 grams/day) were recommended for use as a part of a fat-modified diet to reduce LDL and total cholesterol for people at risk for cardiovascular disease.4
American Dietetic Association (ADA) Statement on Plant Stanol/Sterol Esters: “stanol/sterol esters are effective in lowering serum total cholesterol and LDL cholesterol by approximately 10-15%. Consider using plant stanol/sterol products incorporating 2-3 grams of plant stanol/sterol esters per day.5
Plant sterols and stanols decrease total serum cholesterol and LDL cholesterol concentrations in a dose dependent manner, but not serum HDL cholesterol. Sterols and stanols and their esters are equally effective in lowering total plasma cholesterol concentrations.
Plant sterol esters and plant stanol esters are equally effective during short term use (up to four weeks). However, during longer term use (six to 13 weeks), plant stanol esters are more effective.6
The mechanism(s) by which plant sterols and stanols lower serum cholesterol has not been fully determined. They may compete efficiently with dietary cholesterol for micelle incorporation; displace cholesterol from bile, decreasing reabsorption; and/or decrease hydrolysis of cholesterol esters in the small intestine.
Since plant sterols and stanols may alter micelle formation, it is possible that absorption of fat-soluble nutrients (such as vitamin E and carotenoids) is also diminished.
Daily intake of 1.5 to 3.0 grams of plant sterols or stanols as supplements or in supplemented foods has been shown to be effective for lowering serum cholesterol levels.
Many trials have used several smaller doses (such as with each meal) totaling 1.5 to 3.0 grams of plant sterols or stanols daily. Smaller doses throughout the day appear to be more effective at reducing cholesterol-absorption efficiency than one larger dose.7
Hypocholesterolemic action of sterols and stanols has been identified in clinical trials, regardless of the origin of sterols, saturation of sterols (phytosterol or phytostanol), or the esterification of sterols and stanols.3
More than eighty studies have been conducted with plant sterols and stanols and found no adverse effects. Minor side effects are mild gastrointestinal discomfort including gas, diarrhea, and constipation. In general, phytosterols and phytostanols are well tolerated.8,9,10
Phytosterols and stanols are found in fruits and vegetables. Plant sterols, stanols, esterified sterols or stanols, and mixtures are available both as supplemented foods (such as margarines or yogurts) and as dietary supplements (such as softgels or tablets).
Caution with pregnancy or nursing warranted; consult with a healthcare professional before using. One small study (21 pregnant women) investigated the safety of plant stanol containing margarine during pregnancy. Although the daily use of the spread generally appeared safe, the infants' serum beta-carotene was lowered at one month of age.14
Information on the relationship between substances and disease is provided for general information, in order to convey a balanced review of the scientific literature. In many cases the relationship between a substance and a disease is tentative and additional research is needed to confirm such a relationship.
Plant stanol supplementation decreases serum triacylglycerols in subjects with overt hypertriglyceridemia.
A small, randomized, placebo-controlled, parallel design study investigated the efficacy of plant stanol supplemented margarine for reduction of triacylglycerols in people with hypertriglyceridemia. Twenty-eight people with elevated triacylglycerols (greater than 1.7 mmol/L) participated in the four week trial. After a one-week run-in period (were all participants consumed a control margarine without added plant stanols), participants were randomly assigned to receive either the control margarine or a plant stanol ester enriched margarine providing 2.5 g plant stanol esters daily. Compared with the control group, total serum cholesterol and LDL cholesterol were significantly decreased (6.7%, P=0.015; 9.5%, P=0.041 respectively). Supplementation with plant stanol esters lowered triacylglycerol levels, especially for people with high baseline triacylglycerol levels (more than 2.3 mmol/L; P=0.009). High sensitivity C-reactive protein, glucose, and insulin were not changed. The results of this study indicate that plant stanol ester supplements may help reduce triacylglycerol levels, particularly for people with elevated triacylglycerol concentrations.15
Effect of a plant stanol ester-containing spread, placebo spread, or Mediterranean diet on estimated cardiovascular risk and lipid, inflammatory and haemostatic factors.
A prospective, randomized, placebo-controlled, intention to treat trial investigated the effects of a plant stanol ester containing spread or a Mediterranean diet on risk of cardiovascular disease. One-hundred-fifty mildly hypercholesterolemic people participated in the four month trial. Participants were randomly assigned to one of three groups: (1) plant stanol ester containing spread (2 g plant stanol esters per day); (2) an identical spread without plant stanol esters; or (3) a Mediterranean diet with structured meals provided by dietitians. Total cholesterol, LDL cholesterol, triglycerides, high sensitivity C-reactive protein, blood pressure, and estimated risk of cardiovascular disease were progressively reduced by the Mediterranean diet over four months (24-32%). After one month, the plant stanol ester spread significantly reduced total cholesterol (-14%), LDL cholesterol (-16%), high sensitivity C-reactive protein (-17%), and estimated risk of cardiovascular disease (26-30%). After four months, the estimated risk of cardiovascular disease reduction was comparable in the plant stanol ester supplemented and the Mediterranean diet. These results suggest that plant stanol ester supplements may be beneficial, particularly for people with hypercholesterolemia who choose not to adopt a Mediterranean diet.16
The comparative efficacy of plant sterols and stanols and sterols on serum lipids: a systematic review and meta-analysis.
To evaluate the efficacy of plant sterols versus plant stanols on serum lipid concentrations, a meta-analysis of randomized controlled trials was completed. Fourteen studies were included, involving 531 participants. To evaluate possible differences between plant sterols and plant stanols, weighted mean differences (WMD) were calculated between the means for the differences between plant sterols and plant stanols. Plant sterols and plant stanols were not found to be different in their effects on serum lipid concentrations: total cholesterol (WMD -1.11 mg/dL [-0.0286 mmol/L], 95% confidence interval [CI] -4.12 to 1.90, P=0.47), low-density lipoprotein cholesterol (WMD -0.35 mg/dL [-0.0091 mmol/L], 95% CI -2.98 to 2.28, P=0.79), high-density lipoprotein cholesterol (WMD -0.28 mg/dL [-0.00073 mmol/L], 95% CI -1.18 to 0.62, P=0.54), and triglycerides (WMD -1.80 mg/dL [-0.0203 mmol/L], 95% CI -6.80 to 3.21, P=0.48). The results of this meta-analysis agree with prior findings that plant sterols and plant stanols are equally effective in moderating serum lipid concentrations.17
The effect of adding plant sterols or stanols to statin therapy in hypercholesterolemic patients: systematic review and meta-analysis.
A meta-analysis of randomized controlled trials was completed to evaluate the effects of adding plant sterols or stanols to treatment of hypercholesterolemia with statin therapy. Eight randomized controlled trials were included, involving 306 people with hypercholesterolemia. Meta-analysis revealed that plant sterol or stanol supplements in addition to statin therapy decreased total cholesterol (weighted mean difference (WMD), -14.01 mg/dL [95% CI, -18.66 to -9.37], p<0.0001). LDL cholesterol was also lowered with the addition of plant sterol or stanol supplements (WMD, -13.26 mg/dL [95% CI, -17.34 to -9.18], p<0.0001). HDL cholesterol and triglyceride levels were unaffected by plant sterol or stanol supplementation in addition to statin therapy. The results of this meta-analysis suggest that plant sterol or stanol supplements may help to normalize total and LDL cholesterol for people with hypercholesterolemia currently on statin therapy.
Plant sterols are efficacious in lowering plasma LDL and non-HDL cholesterol in hypercholesterolemic type 2 diabetic and nondiabetic persons.
The effects of plant sterols (1.8 grams/day) on LDL and total cholesterol levels in 14 type 2 diabetic and 15 nondiabetic people were investigated in a placebo-controlled crossover study. Each phase lasted 21 days with a 28 day washout period. LDL cholesterol levels were reduced by 15.1% in nondiabetic and 26.8% in type 2 diabetic subjects, relative to baseline while total cholesterol was reduced by 10.4% for nondiabetic and 14.6% for diabetic subjects. Absolute cholesterol levels were lower in diabetic participants than in nondiabetic participants (P<0.05). Statistically, the reduction in LDL and total cholesterol was the same for the diabetic and nondiabetic groups. This study demonstrated that plant sterol supplements may help to lower LDL and total cholesterol in people with type 2 diabetes.18
Unesterified plant sterols and stanols lower LDL-cholesterol concentrations equivalently in hypercholesterolemic persons.
To evaluate cholesterol lowering efficacy of unesterified plant sterols and stanols, 15 hypercholesterolemic men and women received 1.8 grams/day of unesterified plant sterols (NS), plant stanols (SS), a 50:50 mixture of sterols and stanols (NSS), or cornstarch (placebo). Each dietary treatment phase was a 21-day feeding period, followed by a 4-week washout period during which subjects consumed their habitual diets. The NS and SS group lowered plasma total cholesterol (p<0.01) and LDL cholesterol concentrations (p<0.03), but the most significant impact was in the NSS group, where total and LDL cholesterol concentrations were lowered by 13.1%, and 16.0%, respectively. Cholesterol absorption efficiency was also lower in the treatment groups than in the control group. These results indicate that plant sterols and stanols lower plasma total and LDL cholesterol concentrations in hypercholesterolemic subjects by reducing cholesterol absorption.19
Effects of plant stanol esters supplied in low-fat yoghurt on serum lipids and lipoproteins, non-cholesterol sterols and fat soluble antioxidant concentrations.
Sixty subjects consumed 3 cups yogurt/day emulsified with 3 grams of plant stanol esters or a placebo yogurt for 4 weeks to examine the effect of plant stanol esters on fasting concentrations of plasma lipids and lipid-soluble antioxidants. A 13.7% reduction in LDL cholesterol concentration (p<0.001) was observed in the experimental group, and maximal effects were observed after 1 week. These results produced the same effect as oil-based products enriched with plant stanol/sterol esters that have been shown to lower LDL cholesterol concentrations 10-14%. Decreases in absolute beta-carotene concentrations in all apo-B containing lipoproteins were also observed. The results of this trial indicate that plant stanol esters are effective for lowering LDL cholesterol concentrations.20
Serum lipid and antioxidant responses in hypercholesterolemic men and women receiving plant sterol esters vary by apolipoprotein E genotype.
A randomized, double-blind, placebo-controlled clinical trial investigated the efficacy of plant sterol esters for lowering cholesterol levels. Two-hundred-seventeen hypercholesterolemic adults consumed a low fat, low cholesterol control diet for four weeks, followed by a five week intervention period. Participants were randomly assigned to one of three interventions: a control spread, a spread containing 1.1 g/day plant sterols, or a spread containing 2.2 g/day plant sterols. Participants were evaluated for apolipoprotein E genotype: 26 carried the E2 allele (E2E2 + E2E3), 51 had the E4 allele (E3E4 + E4E4), and 130 were E3 homozygotes. During the intervention period, total cholesterol (TC), LDL cholesterol, and apolipoprotein B concentrations and the TC:LDL and LDL:HDL ratios decreased in only E2 and E3 subjects (P<0.05 vs. control for all). Triacylglycerols only decreased in participants with an E2 genotype (P<0.05 vs. control). Serum carotenoids were monitored as a measure of impact on fat soluble vitamins: significant reductions of beta-carotene and lycopene were found in E2 and E4; alpha-carotene was significantly reduced in E3; cryptoxanthin was significantly reduced in E3 and E4; zeaxanthin was significantly reduced in E4; lycopene was significantly reduced in E2 and E4; and lutein was significantly reduced in E2 carriers (P<0.05 vs. control for all). The results of this study indicate that plant sterol efficacy is affected by apolipoprotein E genotype. 21
Effects of long-term plant sterol or stanol ester consumption on lipid and lipoprotein metabolism in subjects on statin treatment.
A double-blind, randomized trial investigated the long term effects of plant sterol and stanol esters on blood lipids. Fifty-four patients on stable statin therapy participated in the study. Participants consumed a control margarine for a five-week run-in period. Participants were randomly assigned to receive the control margarine, a margarine providing 2.5 g/day plant sterol esters, or a margarine providing 2.5 g/day plant stanol esters for the remainder of the trial. After 85 weeks of intervention, the plant sterol ester margarine reduced LDL cholesterol by 8.7% (P=0.08), relative to control. The plant stanol ester margarine reduced LDL cholesterol by 13.1% (P=0.006), relative to control. These results indicate that long term supplementation of plant sterol or stanol esters is effective for additional lowering of cholesterol concentrations for people already taking statins.22
Effects of low-fat hard cheese enriched with plant stanol esters on serum lipids and apolipoprotein B in mildly hypercholesterolaemic subjects.
A randomized, double-blind, parallel group study investigated the effects of plant stanol esters in cheese on cholesterol concentrations. Sixty-seven mildly hypercholesterolemic men and women participated in the five week study. Participants consumed low-fat cheese supplemented with 2 g plant stanol esters or a control cheese without plant stanol esters daily. Total cholesterol was reduced by 5.8% (P<0.001) in the plant stanol ester supplemented cheese, relative to control. LDL cholesterol was reduced by 10.3% (P<0.001) in the plant stanol ester group relative to control. No changes were observed in HDL cholesterol, triglycerides, or apolipoprotein B. The results of this study indicate that plant stanol esters in low-fat cheese significantly reduced total and LDL cholesterol.23
Reduced-calorie orange juice beverage with plant sterols lowers C-reactive protein concentrations and improves the lipid profile in human volunteers.
A randomized, placebo-controlled, double-blind trial investigated a plant sterol-supplemented orange beverage for improvement of lipid profile. Seventy-seven healthy adults participated in the eight week trial. Participants consumed a reduced calorie orange juice beverage twice daily; the Sterol Bev contained 1 g plant sterols/240 mL beverage, the Placebo Bev did not contain added plant sterols. The Sterol Bev reduced total cholesterol by 5% (P<0.01) and reduced LDL cholesterol by 9.4% (P<0.001) versus baseline or Placebo Bev (P<0.05). C-reactive protein was significantly reduced by the Sterol Bev relative to baseline or Placebo Bev (median reduction: 12% P<0.005). HDL cholesterol was increased by the Sterol Bev (P<0.02). No changes were detected in triacylglycerols, liver function, glucose, vitamin E, or carotenoid concentrations.24
Cocoa flavanol-enriched snack bars containing phytosterols effectively lower total and low-density lipoprotein cholesterol levels.
A randomized, double-blind, parallel arm study investigated the efficacy of phytosterol supplemented snack bars for improving blood lipid profiles. During the six week trial, 67 participants with hypercholesterolemia were randomly assigned to receive either two snack bars containing 1.5 g phytosterol each or two snack bars containing no phytosterol daily. The phytosterol supplementation was associated with a 4.7% reduction in total cholesterol (P<0.01), 6% reduction in LDL cholesterol (P<0.01), and a 7.4% reduction in the ratio of total to HDL cholesterol (P<0.001). No changes were detected in HDL, triglycerides, or lipid-adjusted lycopene, beta-cryptoxanthin, lutein/zeaxanthin, alpha-carotene levels, or levels of serum vitamins A or E. A significant reduction in beta-carotene was found in the phytosterol supplemented group (P<0.05). The results of this study indicate that phytosterol supplemented snack bars are effective for improvement of blood lipid profiles although, a reduction of beta-carotene was noted.25
Effect of low-fat, fermented milk enriched with plant sterols on serum lipid profile and oxidative stress in moderate hypercholesterolemia.
In a randomized, placebo-controlled study a low-fat fermented milk product (yogurt) with or without plant sterols was investigated. During the six week trial, 194 participants consumed two low-fat yogurts daily; in the plant sterol group, the product provided 1.6 g plant sterol daily. Plasma LDL cholesterol was significantly reduced in the plant sterol group by 9.5% after three weeks and by 7.8% after six weeks. No changes were detected for triglycerides, HDL cholesterol, or beta-carotene. By the end of the trial, plasma concentrations of oxidized LDL were decreased in the plant sterol group compared to the control group (-1.73 U/L vs. +1.40 U/L, respectively; P<0.05). As expected, plasma sitosterol concentration was increased by 35% in the plant sterol supplemented group compared to the control group (P<0.001). This study indicates that a plant sterol supplemented fermented milk product is effective for improving the lipid profile.26
Plant sterol-enriched fermented milk enhances the attainment of LDL-cholesterol goal in hypercholesterolemic subjects.
Yogurt supplemented with 1.6 g plant sterols/100 mL was studied in a multicenter, randomized, double-blind, placebo-controlled, parallel design clinical trial. The study included 83 hypercholesterolemic adults. Participants consumed one 100 mL serving of yogurt daily with their main meal which provided 1.6 g plant sterols or no plant sterols (control). The study lasted 42 days. In the plant sterol group, LDL cholesterol was reduced by more than 10% compared to controls (12.2% after 3 weeks, 10.6% after 6 weeks; P=0.001). By the end of the trial, approximately half of the participants in the plant sterol group and approximately 20% of controls, attained their LDL cholesterol target (<3.3 or <2.6 mmol/L for primary and secondary prevention, respectively; P<0.001). HDL cholesterol did not change during the trial. In the plant sterol supplemented group, triglycerides were decreased by 14% (P<0.018). The results of this study suggest that plant sterol supplemented yogurt is an effective way to modify lipid profiles towards healthier values.27
Topic: Efficacy of Tablet Forms of Plant Sterols and Stanols
Effect of plant stanol tablets on low-density lipoprotein cholesterol lowering in patients on statin drugs.
In a placebo-controlled, double-blind study, 26 subjects on statin therapy consuming the American Heart Association Heart Healthy Diet received 1.8 grams/day of soy-derived stanols prepared as lecithin-containing tablets for six weeks. Compared to placebo, LDL cholesterol levels were reduced by 9.1% while total cholesterol was reduced by 5.7% after six weeks. This tablet form of plant stanols was found to be as effective as plant sterol supplemented foods.28
The efficacy of LDL cholesterol lowering by plant stanol/lecithin tablets was investigated. Fifty-two people received 1.26 grams/day of plant stanols either as a rapidly-dissolving tablet (<10 minutes) or a slowly dissolving tablet (>45 minutes) or a placebo for six weeks. Relative to placebo, the rapidly dissolving tablet reduced LDL cholesterol by 10.4% and reduced the ratio of LDL:HDL cholesterol by 11.5%. The slowly disintegrating tablets did not reduce any lipid parameter relative to the placebo. Thus, a rapidly dissolving tablet form of plant stanols with lecithin was found to be effective in lowering LDL cholesterol.29
Topic: Effect on Plasma Fat-Soluble Vitamin/Carotenoid Concentrations
Both free and esterified plant sterols reduce cholesterol absorption and the bioavailability of beta-carotene and alpha-tocopherol in normocholesterolemic humans.
The effect of 2.2 grams/day of plant sterols or esterified plant sterols on bioavailability of beta-carotene and alpha-tocopherol was investigated in 26 normocholesterolemic men. Subjects consumed a control (low-fat milk beverage) or the low-fat milk beverage plus free or esterified plant sterols for one week. Subjects then consumed a beta-carotene (15 mg) and alpha-tocopherol (30 mg) supplement with breakfast. The bioavailability of beta-carotene was decreased by approximately 50% and of alpha-tocopherol was decreased by approximately 20% by free and esterified plant sterols. Plant sterol esters reduced beta-carotene absorption more than free plant sterols. Both free and esterified plant sterols reduced cholesterol absorption by 60%.30
No changes in serum fat-soluble vitamin and carotenoid concentrations with the intake of plant sterol/stanol esters in the context of a controlled diet.
This study compared the consumption of plant sterol/stanol esters on serum fat-soluble vitamin and carotenoid concentrations. Fifteen subjects were randomly fed a diet containing either margarine (control), margarine with sterol esters (1.92 grams/day), or margarine with stanol esters (1.76 grams/day) over 21 days. No significant differences were found in initial or final serum concentrations of fat-soluble vitamins or carotenoids among the three phases. These results suggest that consumption of esterified plant sterols or stanols does not affect fat-soluble vitamin or carotenoid concentrations when compared to a control diet.31
An increase in dietary carotenoids when consuming plant sterols or stanols is effective in maintaining plasma carotenoid concentrations.
Forty-six subjects with hypercholesterolemia consumed spread without added sterols or stanols (control), a sterol ester spread (2.3 grams) and a stanol ester spread (2.5 grams). With each treatment, subjects were advised to eat five or more servings of fruits and vegetables, and one or more of the servings was to be carrots, sweet potatoes, pumpkin, tomatoes, apricots, spinach or broccoli. Adding one daily serving of vitamin A-rich fruit or vegetable while consuming plant sterol or stanols esters allowed subjects to maintain normal plasma carotenoid concentrations. Thus, it was recommended for individuals to consume an additional serving of a carotenoid-containing fruit or vegetable when consuming plant sterol or stanol products.32
A healthy diet rich in carotenoids is effective in maintaining normal blood carotenoid levels during the daily use of plant sterol-enriched spreads.
A recent mini-review suggested that daily intake of plant sterols/stanols may result in a 10-20% decrease in plasma carotenoid concentrations. Data on carotenoids were pooled from two studies on plant sterols. Subjects with the lowest plasma carotenoid concentrations had the smallest decrease in plasma alpha-, beta-carotene and lycopene concentrations. The mid- and high-tertile subjects demonstrated a higher decrease in alpha- and beta-carotene concentrations. However, the plasma levels of carotenoids and lycopene in the mid and high tertile groups did not reach the levels found in the low tertile group. Numerous factors affect plasma carotenoid levels (dietary habits, vegetable/fruit intake, seasonal variation (10-40%), bioavailability of carotenoids, etc.)33
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