Suhad S. AbuMweis

Plant sterols: factors affecting their efficacy and safety as functional food ingredients

Plant sterols are naturally occurring molecules that humanity has evolved with. Herein, we have critically evaluated recent literature pertaining to the myriad of factors affecting efficacy and safety of plant sterols in free and esterified forms. We conclude that properly solubilized 4-desmetyl plant sterols, in ester or free form, in reasonable doses (0.8–1.0 g of equivalents per day) and in various vehicles including natural sources, and as part of a healthy diet and lifestyle, are important dietary components for lowering low density lipoprotein (LDL) cholesterol and maintaining good heart health. In addition to their cholesterol lowering properties, plant sterols possess anti-cancer, anti-inflammatory, anti-atherogenicity, and anti-oxidation activities, and should thus be of clinical importance, even for those individuals without elevated LDL cholesterol. The carotenoid lowering effect of plant sterols should be corrected by increasing intake of food that is rich in carotenoids. In pregnant and lactating women and children, further study is needed to verify the dose required to decrease blood cholesterol without affecting fat-soluble vitamins and carotenoid status.

Plant sterols/stanols as cholesterol lowering agents: A meta-analysis of randomized controlled trials.

Background Consumption of plant sterols has been reported to reduce low density lipoprotein (LDL) cholesterol concentrations by 5–15%. Factors that affect plant sterol efficacy are still to be determined. Objectives To more precisely quantify the effect of plant sterol enriched products on LDL cholesterol concentrations than what is reported previously, and to identify and quantify the effects of subjects’ characteristics, food carrier, frequency and time of intake on efficacy of plant sterols as cholesterol lowering agents. Design Fifty-nine eligible randomized clinical trials published from 1992 to 2006 were identified from five databases. Weighted mean effect sizes were calculated for net differences in LDL levels using a random effect model. Results Plant sterol containing products decreased LDL levels by 0.31 mmol/L (95% CI, –0.35 to –0.27, P= < 0.0001) compared with placebo. Between trial heterogeneity was evident (Chi-square test, P = <0.0001) indicating that the observed differences between trial results were unlikely to have been caused by chance. Reductions in LDL levels were greater in individuals with high baseline LDL levels compared with those with normal to borderline baseline LDL levels. Reductions in LDL were greater when plant sterols were incorporated into fat spreads, mayonnaise and salad dressing, milk and yoghurt comparing with other food products such as croissants and muffins, orange juice, non-fat beverages, cereal bars, and chocolate. Plant sterols consumed as a single morning dose did not have a significant effect on LDL cholesterol levels. Conclusion Plant sterol containing products reduced LDL concentrations but the reduction was related to individuals’ baseline LDL levels, food carrier, and frequency and time of intake.

Evolution of the human diet: linking our ancestral diet to modern functional foods as a means of chronic disease prevention.

The evolution of the human diet over the past 10,000 years from a Paleolithic diet to our current modern pattern of intake has resulted in profound changes in feeding behavior. Shifts have occurred from diets high in fruits, vegetables, lean meats, and seafood to processed foods high in sodium and hydrogenated fats and low in fiber. These dietary changes have adversely affected dietary parameters known to be related to health, resulting in an increase in obesity and chronic disease, including cardiovascular disease (CVD), diabetes, and cancer. Some intervention trials using Paleolithic dietary patterns have shown promising results with favorable changes in CVD and diabetes risk factors. However, such benefits may be offset by disadvantages of the Paleolithic diet, which is low in vitamin D and calcium and high in fish potentially containing environmental toxins. More advantageous would be promotion of foods and food ingredients from our ancestral era that have been shown to possess health benefits in the form of functional foods. Many studies have investigated the health benefits of various functional food ingredients, including omega-3 fatty acids, polyphenols, fiber, and plant sterols. These bioactive compounds may help to prevent and reduce incidence of chronic diseases, which in turn could lead to health cost savings ranging from

Phytosterols as functional food ingredients: linkages to cardiovascular disease and cancer.

2 to

β-glucan from barley and its lipid-lowering capacity: a meta-analysis of randomized, controlled trials

3 billion per year as estimated by case studies using omega-3 and plant sterols as examples. Thus, public health benefits should result from promotion of the positive components of Paleolithic diets as functional foods.

The effect of dietary oleic, linoleic, and linolenic acids on fat oxidation and energy expenditure in healthy men

Purpose of reviewTo examine experimental evidence that has examined association of phytosterols and the reduction of the risk of cardiovascular disease and cancer. Recent findingsPhytosterols exist as naturally occurring plant sterols that are present in the nonsaponifiable fraction of plant oils. Phytosterols are plant components that have a chemical structure similar to cholesterol except for the addition of an extra methyl or ethyl group; however, phytosterol absorption in humans is considerably less than that of cholesterol. In fact, phytosterols reduce cholesterol absorption, although the exact mechanism is not known, and thus reduce circulating levels of cholesterol. The efficacy of phytosterols as cholesterol-lowering agents have been shown when incorporated into fat spreads as well as other food matrices. In addition, phytosterols have been combined with other beneficial dietary components including fish and olive oils, psyllium and beta-glucan to enhance their effect on risk factors of cardiovascular disease. Phytosterols appear not only to play an important role in the regulation of cardiovascular disease but also to exhibit anticancer properties. A side effect associated with the consumption of phytosterols is that they reduce the blood levels of carotenoid. Nevertheless, it has been suggested that compensation for this impact on serum carotenoid levels can occur either by increasing the intake of carotenoid-rich foods or by taking supplements containing these carotenoids. SummaryDietary phytosterols appear to play an important role in the regulation of serum cholesterol and to exhibit anticancer properties.

Plant sterol consumption frequency affects plasma lipid levels and cholesterol kinetics in humans

Background/Objectives:To more precisely quantify the effect of barley β-glucan on blood lipid concentrations in humans and to examine the factors that could affect its efficacy.Subjects/Methods:Eleven eligible randomized clinical trials published from 1989 to 2008 were identified from nine databases. Weighted mean effect sizes were calculated for net differences in lipid profile using a random effect model (RevMan 4.2).Results:Overall, barley and β-glucan isolated from barley lowered total and low-density lipoprotein (LDL) cholesterol concentrations by 0.30 mmol/l (95% confidence interval (CI): −0.39 to −0.21, P<0.00001) and 0.27 mmol/l (95% CI: −0.34 to −0.20, P<0.00001), respectively, compared with control. The pattern of cholesterol-lowering action of barley in this analysis could not be viewed as a dose-dependent response. There were no significant subgroup differences by type of intervention and food matrix.Conclusions:Increased consumption of barely products should be considered as a dietary approach to reduce LDL cholesterol concentrations.

Cholesterol-lowering efficacy of plant sterols in low-fat yogurt consumed as a snack or with a meal.

Studies have shown that the long chain fatty acid composition of a dietary fat influences whether it will be partitioned for either energy or storage. The objective of this study was to compare the effects of 3 oils differing in fatty acid composition on postprandial energy expenditure and macronutrient oxidation in healthy normal-weight men. Using a randomized crossover design, 15 subjects consumed breakfast meals containing 60% of energy as fat. The principal source of fat was (a) olive oil rich in oleic acid (18:1n-9), (b) sunflower oil rich in linoleic acid (18:2n-6), or (c) flaxseed oil rich in linolenic acid (18:3n-3). Measurements of resting metabolic rate, thermic effect of food, and postprandial energy expenditure were conducted with indirect calorimetry that recorded O(2) consumed and CO(2) produced one-half hour before meal consumption and 6 hours after meal consumption. Fat and carbohydrate oxidation rates were calculated from nonprotein gaseous exchange. Olive oil feeding showed a significant overall increase in energy expenditure compared with flaxseed oil (P < .0006) and a trend to increased energy expenditure compared with sunflower oil (P < .06). None of the 3 treatments exhibited significant effects on fat or carbohydrate oxidation. In conclusion, diets rich in oleic acid derived from olive oil may offer increased oxidation translating into increased energy expenditure postprandially.

High basal fractional cholesterol synthesis is associated with nonresponse of plasma LDL cholesterol to plant sterol therapy

Background/Objectives:To compare the efficacy of single versus multiple doses of plant sterols on circulating lipid level and cholesterol trafficking.Subjects/Methods:A randomized, placebo-controlled, three-phase (6 days/phase) crossover, supervised feeding trial was conducted in 19 subjects. Subjects were provided (i) control margarine with each meal; (ii) 1.8 g/day plant sterols in margarine with breakfast (single-BF) and control margarine with lunch and supper or (iii) 1.8 g/day plant sterols in margarine divided equally at each of the three daily meals (three times per day).Results:Relative to control, end point plasma low-density lipoprotein (LDL) cholesterol concentrations were lower (P<0.05) after consuming plant sterols three times per day but were not different when consumed once per day (3.43±0.62, 3.22±0.58 and 3.30±0.65 mmol/l, control, three times per day and single-BF, respectively). Relative to the control, end point LDL level was 0.21±0.27 mmol/l (6%) lower (P<0.05) at the end of the three times per day phase. Cholesterol fractional synthesis rate was highest (P<0.05) after the three times per day phase (0.0827±0.0278, 0.0834±0.0245 and 0.0913±0.0221 pool/day, control, single-BF and three times per day, respectively). Cholesterol-absorption efficiency decreased (P<0.05) by 36 and 39% after the three times per day and single-BF phase, respectively, relative to control.Conclusions:Present data indicate that to obtain optimal cholesterol-lowering impact, plant sterols should be consumed as smaller doses given more often, rather than one large dose.

Cholesterol-Lowering Efficacy of Plant Sterols/Stanols Provided in Capsule and Tablet Formats: Results of a Systematic Review and Meta-Analysis

Objective: Plant sterols (PS) consumed as a snack may not have the same cholesterol-lowering potential as when consumed with a meal due to poor solubilization. It was hypothesized that the consumption of a single dose, low-fat yogurt rich in PS (1.6 g/d) with a meal over an afternoon snack will lead to favourable changes in plasma lipids, plasma PS concentrations, and cholesterol synthesis without negatively affecting α-tocopherol or carotenoids levels. Methods: Twenty-six hyperlipidemic males and females completed the randomized trial of three phases (control, single PS dose consumed with a meal, or single PS dose as an afternoon snack) while consuming controlled, low-fat diets. Plasma lipids, cholesterol synthesis rates, plasma PS and serum fat-soluble antioxidants were measured at baseline and after 4 weeks. Results: Endpoint total cholesterol (TC) levels after the PS snack phase were decreased (p = 0.04) (5.30 ± 0.2 mmol/L) compared to the control phase (5.53 ± 0.2 mmol/L). However, endpoints for TC (5.37 ± 0.2 mmol/L) for PS dose with a meal were comparable to control phase. Low-density lipoprotein-cholesterol tended to be different (p = 0.06) at the end of the intervention phases (3.51 ± 0.1, 3.43 ± 0.1, and 3.33 ± 0.1 mmol/L; control, meal and snack, respectively). Cholesterol fractional synthesis rates were higher (p = 0.007) by 25.8% and 19.5% at the end of the snack and meal phases, respectively, compared with the control phase. Plasma campesterol and β-sitosterol concentrations, adjusted for TC, were higher (p < 0.01) in the snack phase (2.30 ± 0.3 and 0.54 ± 0.1 μmol/mmol, respectively) and in the meal phase (2.00 ± 0.3 and 0.51 ± 0.1 μmol/mmol, respectively) when compared to the control phase (1.81 ± 0.3 and 0.40 ± 0.1 μmol/mmol, respectively). No changes in α-tocopherol or carotenoids levels were detected after adjusting for TC, for all phases. Conclusion: These results indicate that a single dose of PS in low-fat yogurt, provided as a snack, lowers cholesterol levels but does not alter fat-soluble vitamin or carotenoid concentrations in hyperlipidemic participants.