Safety evaluation of phytosterol esters. Part 5. Faecal short-chain fatty acid and microflora content, faecal bacterial enzyme activity and serum female sex hormones in healthy normolipidaemic volunteers consuming a controlled diet either with or without a phytosterol ester-enriched margarine

Abstract

A study was conducted in 12 healthy males and 12 healthy females (mean age 36 years, mean body mass index 24 kg/m 2), to determine the effect of a margarine enriched with phytosterol esters on faecal short-chain fatty acids (SCFAs) and faecal bacterial enzyme activities, viable faecal microflora count, female sex hormones and serum cholesterol concentrations. The study design was a two-period, parallel dosing, randomized, placebo-controlled dietary study. Under controlled dietary conditions, participants consumed 40 g of the control margarine for 21 and 28 consecutive days for males and females, respectively. This was followed immediately by the second part of the study where subjects were equally and randomly allocated to consume daily 40 g of either the control or the test margarine, containing 8.6 g vegetable oil phytosterols (a mixture of β-sitosterol, campesterol and stigmasterol), also for 21 or 28 days. All females were shown to have a regular menstrual cycle and were on an established method of contraception not involving oral contraceptives. When compared with the control group values, the test group showed a significant reduction in serum total and LDL cholesterol concentrations of 18 and 23% (P<0.001; P<0.001) respectively, in faecal lactic acid concentration (P=0.039) and in serum progesterone levels (P=0.021). There were no other significant treatment effects. Within each group a number of significant changes occurred compared to baseline. In the test group, faecal lactic acid concentration and the ratio of acetic acid:total SCFA; and the ratio of butyric acid:total SCFA, in the control group were both significantly reduced ( P=0.016). Compared to baseline, azo-reductase activity was significantly reduced in the control group ( P=0.047). Total faecal aerobes ( P=0.028), lactobacilli ( P=0.003) and staphylococci ( P=0.025) content was also significantly reduced in the control group, while in the test group only lactobacilli content was reduced ( P=0.019). Of the significant findings reported in this study, none was considered to be of biological importance except the beneficial reduction in serum total and LDL-cholesterol concentrations. The daily consumption of a margarine enriched with 8.6 g vegetable oil phytosterols did not affect the bacterial profile or the metabolic activities of the gut microflora, nor did it result in biologically relevant effects on serum female sex hormone levels. The margarine enriched with the vegetable oil phytosterols was well tolerated by both male and female volunteers.