Blood lipid responses to plant stanol ester supplementation and aerobic exercise training

Analytical Strategies to Analyze the Oxidation Products of Phytosterols, and Formulation-Based Approaches to Reduce Their Generation

Phytosterols are a class of lipid molecules present in plants that are structurally similar to cholesterol and have been widely utilized as cholesterol-lowering agents. However, the susceptibility of phytosterols to oxidation has led to concerns regarding their safety and tolerability. Phytosterol oxidation products (POPs) present in a variety of enriched and non-enriched foods can show pro-atherogenic and pro-inflammatory properties. Therefore, it is crucial to screen and analyze various phytosterol-containing products for the presence of POPs and ultimately design or modify phytosterols in such a way that prevents the generation of POPs and yet maintains their pharmacological activity. The main approaches for the analysis of POPs include the use of mass spectrometry (MS) linked to a suitable separation technique, notably gas chromatography (GC). However, liquid chromatography (LC)-MS has the potential to simplify the analysis due to the elimination of any derivatization step, usually required for GC-MS. To reduce the transformation of phytosterols to their oxidized counterparts, formulation strategies can theoretically be adopted, including the use of microemulsions, microcapsules, micelles, nanoparticles, and liposomes. In addition, co-formulation with antioxidants, such as tocopherols, may prove useful in substantially preventing POP generation. The main objectives of this review article are to evaluate the various analytical strategies that have been adopted for analyzing them. In addition, formulation approaches that can prevent the generation of these oxidation products are proposed.

A comparison of the LDL-cholesterol lowering efficacy of plant stanols and plant sterols over a continuous dose range: results of a meta-analysis of randomized, placebo-controlled trials

PURPOSE

To determine if plant stanols and plant sterols differ with respect to their low-density lipoprotein cholesterol (LDL-CH) lowering efficacies across a continuous dose range.

METHODS

Dose-response relationships were evaluated separately for plant stanols and plant sterols and reductions in LDL-CH, using a first-order elimination function.

RESULTS

Altogether, 113 publications and 1 unpublished study report (representing 182 strata) complied with the pre-defined inclusion and exclusion criteria and were included in the assessment. The maximal LDL-CH reductions for plant stanols (16.4%) and plant stanol ester (17.1%) were significantly greater than the maximal LDL-CH reductions for plant sterols (8.3%) and plant sterol ester (8.4%). These findings persisted in several additional analyses.

DISCUSSION AND CONCLUSIONS

Intakes of plant stanols in excess of the recommended 2g/day dose are associated with additional and dose-dependent reductions in LDL-CH, possibly resulting in further reductions in the risk of coronary heart disease (CHD).

Responses of blood lipids and lipoproteins to extended-release niacin and exercise in sedentary postmenopausal women

Niacin and exercise positively alter blood lipids and lipoproteins via different mechanisms. However, the effects of niacin combined with exercise on blood lipid and lipoprotein profiles have not been investigated in sedentary postmenopausal women. The current study examined the responses of blood lipids and lipoproteins to niacin and exercise in 18 sedentary postmenopausal women, who underwent four conditions: no-niacin rest, no-niacin exercise, niacin rest, and niacin exercise. Participants ingested 1,000 mg/day of extended-release niacin for 4 weeks during the niacin condition. As an exercise treatment, participants performed a single bout of exercise on a treadmill at 60% heart rate reserve until 400 kcal were expended. Extended-release niacin without the exercise intervention significantly (p < .001) increased high-density lipoprotein cholesterol and high-density lipoprotein-2 cholesterol by 12.4% and 33.3%, respectively, and decreased the total cholesterol to high-density lipoprotein cholesterol ratio by 14.8%. Thus, 4 weeks of 1,000 mg/day of extended-release niacin can improve the blood lipid and lipoprotein profiles in sedentary postmenopausal women.

Continuous dose-response relationship of the LDL-cholesterol-lowering effect of phytosterol intake

Phytosterols (plant sterols and stanols) are well known for their LDL-cholesterol (LDL-C)-lowering effect. A meta-analysis of randomized controlled trials in adults was performed to establish a continuous dose-response relationship that would allow predicting the LDL-C-lowering efficacy of different phytosterol doses. Eighty-four trials including 141 trial arms were included. A nonlinear equation comprising 2 parameters (the maximal LDL-C lowering and an incremental dose step) was used to describe the dose-response curve. The overall pooled absolute (mmol/L) and relative (%) LDL-C-lowering effects of phytosterols were also assessed with a random effects model. The pooled LDL-C reduction was 0.34 mmol/L (95% CI: -0.36, -0.31) or 8.8% (95% CI: -9.4, -8.3) for a mean daily dose of 2.15 g phytosterols. The impacts of subject baseline characteristics, food formats, type of phytosterols, and study quality on the continuous dose-response curve were determined by regression or subgroup analyses. Higher baseline LDL-C concentrations resulted in greater absolute LDL-C reductions. No significant differences were found between dose-response curves established for plant sterols vs. stanols, fat-based vs. non fat-based food formats and dairy vs. nondairy foods. A larger effect was observed with solid foods than with liquid foods only at high phytosterol doses (>2 g/d). There was a strong tendency (P = 0.054) towards a slightly lower efficacy of single vs. multiple daily intakes of phytosterols. In conclusion, the dose-dependent LDL-C-lowering efficacy of phytosterols incorporated in various food formats was confirmed and equations of the continuous relationship were established to predict the effect of a given phytosterol dose. Further investigations are warranted to investigate the impact of solid vs. liquid food formats and frequency of intake on phytosterol efficacy.

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.