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PubMed2002

Safety evaluation of phytosterol esters. Part 7. Assessment of mutagenic activity of phytosterols, phytosterol esters and the cholesterol derivative, 4-cholesten-3-one.

Phytosterol esters are phytosterols derived from vegetable oils following esterification to fatty acids. When phytosterols are added to foods, they inhibit the absorption of dietary and endogenous cholesterol and thereby reduce blood cholesterol concentrations. As part of a comprehensive programme of safety assessment, the mutagenic potential of phytosterols and phytosterol esters has been assessed in a bacterial mutation assay and an in vitro chromosome aberration assay. In addition, an in vitro mammalian cell gene mutation assay and two in vivo mutagenicity studies, namely rat bone marrow micronucleus and liver unscheduled DNA synthesis (UDS) assays, were conducted on phytosterol esters only. Phytosterols and phytosterol esters did not show any evidence of mutagenic activity in any of these assays. A breakdown product of cholesterol is 4-cholesten-3-one and thus the amount of 4-cholesten-3-one in the gut may increase following supplementation of foods with phytosterol-esters. 4-cholesten-3-one had been previously reported as mutagenic but, due to various shortcomings, these data could not be used to assess the mutagenic activity of 4-cholesten-3-one. The mutagenic activity of 4-cholesten-3-one and its major faecal by-products, 5beta-cholestan-3-one, was assessed in two in vitro assays, a bacterial mutation assay and an in vitro chromosome aberration assay. Neither 4-cholesten-3-one nor 5beta-cholestan-3-one showed evidence of mutagenic activity in these assays.

Animals↗
PubMed2004

Oral absorption of phytosterols and emulsified phytosterols by Sprague-Dawley rats.

Clinical studies have demonstrated that consumption of phytosterol esters in lipid-based foods decreases serum concentrations of total and LDL cholesterol. These substances represent minimal potential for adverse effects when consumed orally because of their low bioavailability. However, some studies have reported estrogenic and other effects in laboratory animals treated parenterally with phytosterols, demonstrating that these substances may have the potential to cause adverse effects if absorbed. Water-soluble phytosterols have been prepared by formulation with emulsifiers to expand delivery options to include non-lipid-based foods. However, emulsifiers are used as excipients in the formulation of lipophilic pharmaceuticals to increase solubility, thereby increasing their absorption. Therefore, oral consumption of emulsified water-soluble phytosterols could potentially increase their absorption. In the current study, absorption of phytosterols prepared as water-soluble emulsified micelles with two different food-grade emulsifiers was evaluated in Sprague-Dawley rats and compared with absorption of non-micellar free phytosterols and esterified phytosterol mixtures dissolved in a lipophilic vehicle (soybean oil). Rats were dosed via gavage with 42 mg/kg of formulated phytosterol preparations. Blood was collected at 8, 16, 24, and 32 hours, extracted with hexane, derivatized with benzoyl chloride, and analyzed by high-performance liquid chromatography to determine concentrations of beta-sitosterol, and campesterol. Plasma concentrations and AUC(0-32 hours) [microg/mL/h] of beta-sitosterol and campesterol were lower in plasma obtained from rats treated with emulsified phytosterol preparations than in animals treated with free phytosterols dissolved in soybean oil. Because the pharmacokinetic profile of water-soluble phytosterols is similar to that of phytosterols administered in a lipid vehicle, the safety profile is likely to be the same as that of phytosterols and phytosterol esters in currently used applications.

Absorption↗
PubMed2004

Safety evaluation of phytosterol esters. Part 8. Lack of genotoxicity and subchronic toxicity with phytosterol oxides.

Vegetable oil spreads containing phytosterol-esters are marketed as a cholesterol-lowering functional food in more than 20 countries worldwide. An extensive package of safety data has shown phytosterol-esters to be safe for human use. However, even though phytosterols are very stable molecules, oxidation may occur at low levels under extreme heating conditions, resulting in phytosterol oxides. As there is some suggestion of adverse biological effects in the literature for the related cholesterol oxidation products, safety data have been generated for phytosterol oxides. A phytosterol oxide concentrate (POC) was generated by prolonged heating of phytosterol-esters in the presence of oxygen. The genotoxicity and subchronic toxicity of this mixture was assessed in a series of in vitro genotoxicity assays (bacterial mutation, chromosome aberration and micronucleus) and a subchronic feeding study in the rat. Results showed that a phytosterol oxide concentrate containing approximately 30% phytosterol oxides did not possess genotoxic potential and no obvious evidence of toxicity when administered in the diet of the rat for 90 consecutive days. In the latter study, a NOEL was established at an estimated dietary level of phytosterol oxides of 128 mg/kg/day for males and 144 mg/kg/day for females. In conclusion, these materials have been shown to raise no obvious concerns for human safety.

Administration, Oral↗
PubMed2003

Inhibition of cholesterol absorption by phytosterol-replete wheat germ compared with phytosterol-depleted wheat germ.

BACKGROUND: Low-fat vegetable foods contain phytosterols, but it is not known whether they are in biologically active forms or whether their concentrations are high enough to reduce cholesterol absorption and favorably affect lipid metabolism. OBJECTIVE: The objective was to establish whether the selective removal of phytosterols from wheat germ would increase the cholesterol absorption measured from test meals composed of wheat germ muffins. DESIGN: Wheat germ, which has a high content of phytosterols relative to total fat, was chosen as a low-fat test food. Cholesterol absorption was measured 3 times in 10 subjects. Each test meal was a muffin containing 30 mg heptadeuterated cholesterol tracer and, in random order, 80 g original wheat germ containing 328 mg phytosterols, wheat germ from which phytosterols had been selectively extracted, or extracted wheat germ reconstituted with purified phytosterols. Changes in cholesterol absorption were monitored by the measurement of tracer enrichment of plasma cholesterol 4 and 5 d after each meal with the use of negative ion mass spectrometry. RESULTS: Tracer enrichment of plasma cholesterol was 42.8% higher after consumption of phytosterol-free wheat germ than after that of the original wheat germ (0.415 +/- 0.035 compared with 0.291 +/- 0.024 micro mol tracer/mmol cholesterol; P < 0.01). Tracer enrichment of plasma cholesterol was not significantly different between the wheat germ with extracted-and-reconstituted phytosterol (0.305 +/- 0.022 micro mol tracer/mmol cholesterol) and the original wheat germ. CONCLUSION: The efficiency of cholesterol absorption from test meals was substantially lower after consumption of original wheat germ than after consumption of phytosterol-free wheat germ, which suggests that endogenous phytosterols in wheat germ and possibly in other low-fat vegetable foods may have important effects on cholesterol absorption and metabolism that are independent of major nutrients.

Absorption↗
PubMed1999

Safety evaluation of phytosterol esters. Part 4. Faecal concentrations of bile acids and neutral sterols in healthy normolipidaemic volunteers consuming a controlled diet either with or without a phytosterol ester-enriched margarine.

A study was conducted in 12 healthy males and 12 females (mean age 36 years) to assess the impact of a margarine enriched with phytosterol esters on faecal concentrations of bile acids and sterols. During the run-in period, volunteers consumed 40 g of a control margarine for 21 consecutive days if male, and for 28 days if female. Half of the volunteers were then randomly allocated to consume the control margarine for another 21 or 28 days, respectively. The remaining subjects consumed 40 g of a margarine containing 8.6 g vegetable oil phytosterol (46% (w/w) beta-sitosterol, 26% campesterol, 20% stigmasterol). Throughout the total study subjects consumed the same diet adjusted for individual energy requirements. The phytosterol ester-enriched spread significantly enhanced faecal neutral sterol concentrations from about 40 mg/g to 190 mg/g dry weight faeces. Faecal neutral sterol metabolites increased from about 30 mg/g to about 50 mg/g. The major parent sterols excreted were cholesterol, sitosterol, campesterol and stigmasterol. Sitosterol, campesterol and stigmasterol comprised 28%, 15% and 12% of the total faecal neutral sterols, reflecting the composition of the sterol enriched margarine. The major sterol metabolites excreted were metabolites formed by, predominantly, oxidation at the 3-position and metabolites saturated at the 5,6 position in a beta-configuration. Faecal secondary bile acid concentration was reduced by vegetable oil sterols from 7.6 mg/g dry faeces to 6.0 mg/g. Consumption of vegetable oil phytosterols slightly but significantly increased the faecal concentration of 4-cholesten-3-one. However, 4-cholesten-3-one concentration remained very low (< 2 mg/g) and in line with values reported in the literature for subjects fed high or low fat diets. No sterol oxides could be detected in the faeces. We conclude that in healthy adult males and females a high intake of vegetable oil phytosterol esters does increase the amount of neutral sterols in the faeces, as expected, but does not result in the increased formation of bile acids or sterol metabolites.

Adult↗
PubMed2006

Separation of Delta5- and Delta7-phytosterols by adsorption chromatography and semipreparative reversed phase high-performance liquid chromatography for quantitative analysis of phytosterols in foods.

A method for the separation, isolation, and identification of phytosterols was developed. A commercial phytosterols mixture, Generol 95S, was fractionated first by adsorption silica gel column chromatography and then separated by means of a semipreparative reverse phase high-performance liquid chromatography fitted with a Polaris C8-A column (250 mm x 10 mm i.d., 5 microm) using isocratic acetonitrile:2-propanol:water (2:1:1, v/v/v) as the mobile phase. Milligram scales of six individual phytosterols, including citrostadienol, campesterol, beta-sitosterol, Delta7-avenasterol, Delta7-campesterol, and Delta7-sitosterol, were obtained. Purities of these isolated sterols were 85-98%. Relative response factors (RRF) of these phytosterols were calculated against cholestanol as an authentic commercial standard. These RRF values were used to quantify by gas chromatography-mass spectrometry (GC-MS) the phytosterols content in a reference material, oils, and chocolates.

Adsorption↗
PubMed2000

The safety evaluation of phytosterol esters. Part 6. The comparative absorption and tissue distribution of phytosterols in the rat.

As part of an extensive safety evaluation programme, a series of studies has been conducted to determine the fate of phytosterols in the rat. Rats were dosed by oral gavage with 14C-labelled samples of cholesterol, beta-sitosterol or beta-sitostanol or (3)H-labelled samples of beta-sitostanol, campesterol, campestanol or stigmasterol dissolved in sunflower seed oil. Urine and faeces were collected for up to 96 hours after dosing. There was no quantification of biliary excreted material in these studies. Animals were sacrificed and either prepared for whole body autoradiography or tissues and carcass remains were assayed for 14C or (3)H. The overall absorption of phytosterols was low as judged by tissue and carcass levels of radioactivity. Elimination from the body was mainly in the faeces and was initially very rapid, but traces of material were still being excreted at 4 days after dosing. While total absorption of the phytosterols could not be fully quantified without biliary excretion data, it was clear that cholesterol was absorbed to the greatest extent (27% of the dose in females at 24 hours). Campesterol (13%) was absorbed more than beta-sitosterol and stigmasterol (both 4%) which were absorbed more than beta-sitostanol and campestanol (1-2%). The absorption of phytosterols was slightly greater in females than males. For each test material, the overall pattern of tissue distribution of radioactivity was similar, with the adrenal glands, ovaries and intestinal epithelia showing the highest levels and the longest retention of radioactivity.

Animals↗
PubMed1999

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.

A study was conducted in 12 healthy males and 12 healthy females (mean age 36 years, mean body mass index 24 kg/m2), 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 beta-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.

Bacteria↗
PubMed1999

Safety evaluation of phytosterol esters. Part 2. Subchronic 90-day oral toxicity study on phytosterol esters--a novel functional food.

Phytosterol esters (PE) are intended for use as a novel food ingredient, primarily in margarines and spreads as a functional component with plasma cholesterol lowering activity. Phytosterols and their esters are present naturally in vegetable oils and on average people consume 200 mg/day, but their consumption at this level is not sufficient to lower plasma cholesterol levels. Therefore, through the incorporation of PE into margarines/spreads, the intake can be increased by approximately 10-fold by consuming the PE-containing margarine/spread at normal intake levels. As part of an extensive programme of safety evaluation studies a subchronic rat toxicity study has been conducted in which groups of Alpk:AP(f)SD (Wistar derived) rats (20 males and 20 females/group) were fed diets containing PE at levels of 0, 0.16, 1.6, 3.2 and 8.1% (w/w) in the diet for 90 days. Throughout the study, clinical observations, body weights, and food and water consumption were measured. At the end of the study the rats were subjected to a full post-mortem examination, cardiac blood samples were taken for clinical pathology, selected organs were weighed, and a full tissue list was taken for subsequent histological examination. There were no treatment-related changes that were considered to be of toxicological significance. Therefore, a nominal PE concentration of 8.1% was considered to be the no-observed-adverse- effect level (NOAEL) following daily oral administration to rats for 90 days. This was equivalent to a dose of 6.6 g/kg body weight/day PE or 4.1 g/kg/day phytosterol.

Administration, Oral↗
PubMed1991

Relationships of serum plant sterols (phytosterols) and cholesterol in 595 hypercholesterolemic subjects, and familial aggregation of phytosterols, cholesterol, and premature coronary heart disease in hyperphytosterolemic probands and their first-degree relatives.

To assess relationships of serum phytosterols (plant sterols [P]) to serum cholesterol (C), P were measured by gas-liquid chromatography (GLC) in 595 hypercholesterolemics (top C quintile in screening of 3,472 self-referred subjects). A second specific aim was to determine whether high serum P would track over time and whether they would predict familial aggregation of high C, high low-density lipoprotein cholesterol (LDLC), high apolipoprotein (apo) B, and increased premature coronary heart disease (CHD) in hyperphytosterolemic probands and their first-degree relatives. Mean +/- (SD) C was 260 +/- 56 mg/dL, campesterol (CAMP) was 2.10 +/- 1.6 micrograms/mL, stigmasterol (STIG) 1.71 +/- 1.67, sitosterol (SIT) 2.98 +/- 1.61, and total P 6.79 +/- 3.66 micrograms/mL. Serum C correlated with CAMP (r = .15, P less than or equal to .001), STIG (r = .10, P less than or equal to .02), SIT (r = .34, P less than or equal to .0001), and total P (r = .29, P less than or equal to .0001). High serum CAMP and STIG were associated with a personal or family history of CHD in subjects less than or equal to age 55 years (premature CHD). In 21 hyperphytosterolemic probands who initially had at least one P at or above the 95th percentile and a second P at or above the 75th percentile, P were remeasured 2 years later. Initial and 2-year follow-up CAMP, STIG, and SIT did not differ (P greater than .7). Initial and follow-up CAMP were correlated (r = .47, P = .03).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1999

Safety evaluation of phytosterol esters. Part 3. Two-generation reproduction study in rats with phytosterol esters--a novel functional food.

Phytosterol esters (PE) are intended for use as a novel food ingredient with plasma cholesterol lowering activity which works by inhibiting the absorption of cholesterol from the gut. Although PE are naturally present in the normal diet, the levels are insufficiently large to ensure lowering of plasma cholesterol levels. Therefore PE may be added to spreads to achieve the desired cholesterol lowering activity. As part of an extensive programme of safety evaluation studies a two-generation reproduction study has been conducted in Wistar rats, in which the possible effect of PE on male and female reproductive performance and on the growth and development of the offspring was studied. Rats were fed diets containing PE at levels of 0, 1.6, 3.2 and 8.1% (w/w) PE over two successive generations, and a wide range of reproductive and developmental parameters, including sexual maturation parameters and oestrous cycle length, were determined. Macroscopic and microscopic examinations were conducted including a histological examination of selected organs from F1- and F2-weanlings and from F0- and F1-parental animals. Daily clinical observations did not reveal any unusual findings. In both generations, no effects of PE were observed on pup mortality (calculated on litter basis), precoital time, mating index, male and female fertility index, female fecundity index, gestation index, duration of gestation, number of females with stillborn pups, post-implantation loss and pup development. Furthermore, PE had no effect on sexual maturation parameters (preputial separation and vaginal opening) and oestrous cycle length. In addition, there were no dose-related effects on selected organs following histological examination. In conclusion, dietary administration of up to 8.1% PE (equivalent to a dose of 2.5 to 9.1 g PE/kg body weight/day, dependent on the period of the study) during two generations had no effect on reproduction of parental F0- and F1-generation Wistar rats, nor on the development of the F1- and F2-pups, nor on the sexual maturation of the F1-weanlings. Therefore, a nominal dietary PE concentration of 8.1% (equivalent to a dose of 2.5-9.1 g PE/kg body weight/day or 1.54-5.62 g phytosterol/kg body weight/day dependent on the period of the study) was considered to be the no-observed-adverse-effect level following daily oral administration of PE for two successive generations.

Animals↗
PubMed2002

Phytosterols, phytostanols, and their conjugates in foods: structural diversity, quantitative analysis, and health-promoting uses.

Phytosterols (plant sterols) are triterpenes that are important structural components of plant membranes, and free phytosterols serve to stabilize phospholipid bilayers in plant cell membranes just as cholesterol does in animal cell membranes. Most phytosterols contain 28 or 29 carbons and one or two carbon-carbon double bonds, typically one in the sterol nucleus and sometimes a second in the alkyl side chain. Phytostanols are a fully-saturated subgroup of phytosterols (contain no double bonds). Phytostanols occur in trace levels in many plant species and they occur in high levels in tissues of only in a few cereal species. Phytosterols can be converted to phytostanols by chemical hydrogenation. More than 200 different types of phytosterols have been reported in plant species. In addition to the free form, phytosterols occur as four types of "conjugates," in which the 3beta-OH group is esterified to a fatty acid or a hydroxycinnamic acid, or glycosylated with a hexose (usually glucose) or a 6-fatty-acyl hexose. The most popular methods for phytosterol analysis involve hydrolysis of the esters (and sometimes the glycosides) and capillary GLC of the total phytosterols, either in the free form or as TMS or acetylated derivatives. Several alternative methods have been reported for analysis of free phytosterols and intact phytosteryl conjugates. Phytosterols and phytostanols have received much attention in the last five years because of their cholesterol-lowering properties. Early phytosterol-enriched products contained free phytosterols and relatively large dosages were required to significantly lower serum cholesterol. In the last several years two spreads, one containing phytostanyl fatty-acid esters and the other phytosteryl fatty-acid esters, have been commercialized and were shown to significantly lower serum cholesterol at dosages of 1-3 g per day. The popularity of these products has caused the medical and biochemical community to focus much attention on phytosterols and consequently research activity on phytosterols has increased dramatically.

Animals↗
PubMed2000

Vegetable oils high in phytosterols make erythrocytes less deformable and shorten the life span of stroke-prone spontaneously hypertensive rats.

Previous studies have shown that canola oil (CA), compared with soybean oil (SO), shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats, a widely used model for hemorrhagic stroke. SHRSP rats are highly sensitive to dietary cholesterol manipulations because a deficiency of membrane cholesterol makes their cell membranes weak and fragile. Phytosterols, abundant in CA but not in SO, can inhibit the absorption of cholesterol and also replace a part of cholesterol in cell membranes. This study was performed to determine whether the high concentration of phytosterols in CA might account for its life-shortening effect on SHRSP rats. Male, 35-d-old SHRSP rats (n = 28/group) were fed semipurified diets containing CA, SO, CA fortified with phytosterols (canola oil + phytosterols, CA + P), SO fortified with phytosterols (soybean oil + phytosterols, SO + P), corn oil (CO), olive oil (OO) or a fat blend that mimicked the fat composition of a representative Canadian diet (Canadian fat mimic, CFM; 10 g/100 g diet). These fats provided 97, 36, 207, 201, 114, 27 and 27 mg phytosterols/100 g diet, respectively. Ten rats from each group were killed after 30-32 d for blood and tissue analyses. The remaining rats (18/group) were used for determination of life span. The life span of SHRSP rats fed the high phytosterol oils (CA, CA + P, SO + P and CO) was significantly (P<0.05) shorter than that of CFM- and SO-fed rats. At 30-32 d, the groups fed the high phytosterol oils had greater levels of phytosterols and significantly (P<0.05) higher ratios of phytosterols/cholesterol in plasma, RBC, liver and kidney, and a significantly (P<0.05) lower RBC membrane deformabilty index than the groups fed oils low in phytosterols (SO, OO and CFM). The mean survival times were correlated with RBC deformability index (r(2) = 0.91, P = 0.0033) and cholesterol concentration (r(2) = 0.94, P = 0.0016), and inversely correlated with RBC phytosterol concentration (r(2) = 0.58, P = 0.0798) and phytosterols/cholesterol (r(2) = 0.65, P = 0.0579), except in the OO group. This study suggests that the high concentration of phytosterols in CA and the addition of phytosterols to other fats make the cell membrane more rigid, which might be a factor contributing to the shortened life span of SHRSP rats.

Animals↗
PubMed2003

Phytosterol additives increase blood pressure and promote stroke onset in salt-loaded stroke-prone spontaneously hypertensive rats.

1. To assess the effect of dietary phytosterol on stroke and the lifespan of salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP), we investigated the effects of the addition of phytosterol to soybean oil (phytosterol content: 0.3%) on stroke onset, lifespan following onset of stroke and overall lifespan compared with canola oil (phytosterol content: 0.9%). 2. Six-week-old male SHRSP were fed a test diet prepared by the addition of canola oil (CA diet), soybean oil (SO diet), soybean oil plus 0.6% phytosterol (SO + 0.06P diet) or soybean oil plus 4.5% phytosterol (SO + 0.45P diet) as a 10% fat source. 3. Systolic blood pressure (SBP) increased in the SO + 0.06P and SO + 0.45P groups compared with the SO group and the increase was dependent on the amount of phytosterol added, indicating that the addition of phytosterol to soybean oil may promote an increase in SBP in salt-loaded SHRSP. 4. The onset of stroke was shortest in the SO + 0.45P group and survival after the onset of stroke was shortest in the CA group. Consequently, the SO + 0.45P and CA groups showed marked lifespan shortening, indicating that a fivefold greater amount of phytosterol was required to produce an effect equivalent to that of canola oil. 5. Investigation of the mRNA expression of ATP-binding cassette (ABC) transporters involved in intestinal phytosterol absorption indicated significant decreases in the intestinal mRNA expression of Abcg5 and Abcg8 in SHRSP and Wistar-Kyoto rats compared with Wistar rats. 6. In conclusion, the addition of phytosterol to soybean oil elevated SBP and promoted the onset of stroke, which may cause a reduction in survival time. However, a fivefold greater amount of phytosterol was required to produce an effect that was equivalent to the survival time-shortening effect of canola oil. The significant decrease in the intestinal mRNA expression of Abcg5 and Abcg8 in SHRSP may be responsible, at least in part, for the unfavourable effects observed following the addition of phytosterol.

ATP-Binding Cassette Transporters↗
PubMed2005

A comparison of the effect of medium- vs. long-chain triglycerides on the in vitro solubilization of cholesterol and/or phytosterol into mixed micelles.

Despite clinical evidence of the cholesterol-lowering effects of phytosterols, the exact mechanisms involved are still unclear. Displacement of cholesterol by phytosterols from mixed micelles, which is due to their greater hydrophobicity, is one of the hypotheses for the lumenal effects contributing to the reduction of intestinal cholesterol absorption. In this study a dynamic in vitro lipolysis method was used to examine the solubilization behavior of cholesterol and/or phytosterols during lipolysis to probe the efficacy of cholesterol displacement from mixed micelles by phytosterols. The effects of lipid chain length on sterol solubilization were studied by using microcrystalline suspensions containing 17% phytosterol or cholesterol, formulated in long-chain TG (LCT) and medium-chain TG (MCT). When digesting cholesterol-suspended in LCT, the entire cholesterol dose was incorporated into the micellar phase. For the cholesterol formulation suspended in MCT, 50.3% of the initial dose was recovered in the micelles. Under the respective conditions, we observed lower solubilization of phytosterols than of cholesterol (roughly fourfold). Only 25% of the initial phytosterol dose was solubilized from suspensions formulated with LCT, and 13% was solubilized from MCT formulations. Co-administration of phytosterol and cholesterol suspensions showed a significant reduction of cholesterol solubilization, particularly when dosed in MCT, with approximately 25% of the cholesterol dose solubilized. Insignificant amounts of cholesterol were displaced by phytosterols when cholesterol was presolubilized in the mixed micelles. The results show that, compared with LCT, mixed micelles containing MCT lipolysis products have a reduced solubilizing capacity for cholesterol, which adds to the effectiveness of the phytosterols in displacing cholesterol. This suggests potential benefits of using medium chain length lipids in cholesterol-lowering phytosterol products.

Cholesterol↗
PubMed2004

Pearling barley and rye to produce phytosterol-rich fractions.

Because of the positive health effects of phytosterols, phytosterol-enriched foods and foods containing elevated levels of natural phytosterols are being developed. Phytosterol contents in cereals are moderate, whereas their levels in the outer layers of the kernels are higher. The phytosterols in cereals are currently underutilized; thus, there is a need to create or identify processing fractions that are enriched in phytosterols. In this study, pearling of hulless barley and rye was investigated as a potential process to make fractions with higher levels of phytosterols. The grains were pearled with a laboratory-scale pearler to produce pearling fines and pearled grains. Lipids were extracted by accelerated solvent extraction, and nonpolar lipids were analyzed by normal-phase HPLC with ELSD and UV detection. Total sterol analyses were performed by GC. After a 90-s pearling, the amounts of pearling fines from hulless barley and rye were 14.6 and 20.1%, respectively, of the original kernel weights. During pearling, higher levels of phytosterols and other lipids were fractionated into the fines. The contents of free sterols and sterols esterified with FA in the fines were at least double those in the whole grains. Pearling fines of hulless barley and rye contained >2 mg/g phytosterol compounds, which makes them a good source of phytosterols and thus valuable raw materials for health-promoting foods.

Food↗
PubMed1995

Dietary phytosterols: a review of metabolism, benefits and side effects.

Most animal and human studies show that phytosterols reduce serum/or plasma total cholesterol and low density lipoprotein (LDL) cholesterol levels. Phytosterols are structurally very similar to cholesterol except that they always contain some substitutions at the C24 position on the sterol side chain. Plasma phytosterol levels in mammalian tissue are normally very low due primarily to poor absorption from the intestine and faster excretion from liver compared to cholesterol. Phytosterols are able to be metabolized in the liver into C21 bile acids via liver other than normal C24 bile acids in mammals. It is generally assumed that cholesterol reduction results directly from inhibition of cholesterol absorption through displacement of cholesterol from micelles. Structure-specific effects of individual phytosterol constituents have recently been shown where saturated phytosterols are more efficient compared to unsaturated compounds in reducing cholesterol levels. In addition, phytosterols produce a wide spectrum of therapeutic effects in animals including anti-tumour properties. Phytosterols have been shown experimentally to inhibit colon cancer development. With regard to toxicity, no obvious side effects of phytosterol have been observed in studies to date, except in individual with phytosterolemia, an inherited lipid disorder. Further characterization of the influence of various phytosterol subcomponents on lipoprotein profiles in humans is required to maximize the usefulness of this non-pharmacological approach to reduction of atherosclerosis in the population.

Animals↗