To evaluate the content of phytosterol oxidation products (POP) of foods with added phytosterols, in total 14 studies measuring POP contents of foods with added phytosterols were systematically reviewed. In non‐heated or stored foods, POP contents were low, ranging from (medians) 0.03–3.6 mg/100 g with corresponding oxidation rates of phytosterols (ORP) of 0.03–0.06%. In fat‐based foods with 8% of added free plant sterols (FPS), plant sterol esters (PSE) or plant stanol esters (PAE) pan‐fried at 160–200°C for 5–10 min, median POP contents were 72.0, 38.1, and 4.9 mg/100 g, respectively, with a median ORP of 0.90, 0.48, and 0.06%. Hence resistance to thermal oxidation was in the order of PAE > PSE > FPS. POP formation was highest in enriched butter followed by margarine and rapeseed oil. In margarines with 7.5–10.5% added PSE oven‐heated at 140–200°C for 5–30 min, median POP content was 0.3 mg/100 g. Further heating under same temperature conditions but for 60–120 min markedly increased POP formation to 384.3 mg/100 g. Estimated daily upper POP intake was 47.7 mg/d (equivalent to 0.69 mg/kg BW/d) for foods with added PSE and 78.3 mg/d (equivalent to 1.12 mg/kg BW/d) for foods with added FPS as calculated by multiplying the advised upper daily phytosterol intake of 3 g/d with the 90% quantile values of ORP. In conclusion, heating temperature and time, chemical form of phytosterols added and the food matrix are determinants of POP formation in foods with added phytosterols, leading to an increase in POP contents. Practical applications: Phytosterol oxidation products (POP) are formed in foods containing phytosterols especially when exposed to heat treatment. This review summarising POP contents in foods with added phytosterols in their free and esterified forms reveals that heating temperature and time, the chemical form of phytosterols added and the food matrix itself are determinants of POP formation with heating temperature and time having the biggest impact. The estimated upper daily intakes of POP is 78.3 mg/d for fat‐based products with added free plant sterols and 47.7 mg/d for fat‐based products with added plant sterol esters. Phytosterols in foods are susceptible to oxidation to form phytosterol oxidation products (POP). This review summarizes literature data regarding POP contents of foods with added phytosterols that were exposed to storage and heat treatments.
This article is available online at http://www.jlr.org Phytosterols or plant sterols are present in most plantbased food products and have structural similarity to cholesterol, differing only in aliphatic side chain length and saturation. Sitosterol, campesterol, and stigmasterol have unsaturated moieties in the sterol core (compared with stanols) and are the major plant sterols in human diets. They are mainly provided by vegetable oils, nuts, unrefi ned grains, and, to a much lower extent, fruits and vegetables ( 1, 2 ). Other important dietary sources of plant sterols or stanols are phytosterol-enriched food products (e.g., margarines, which are typically enriched with the fatty acid esters of plant stanols or sterols) and a variety of enriched low-fat food products (e.g., yogurt, milk preparations, and beverages). The consumption of these esterifi ed plant sterol-enriched foods results in LDL cholesterollowering effects in various groups and other approved health claims ( 3, 4 ). Although the total and LDL cholesterol-lowering effects of plant sterols have been known since the 1950s and repeatedly demonstrated in more recent trials ( 1 ), the detailed mechanistic events behind this metabolic phenomenon as occurring in the intestinal lumen are not yet fully understood. In vitro work has suggested that free plant sterols can be dispersed in mixed micelles, thus displacing free cholesterol moieties and resulting in lower cholesterol availability for uptake by the enterocyte apical brush border membrane. Reduced intestinal absorption of cholesterol in the presence of esterifi ed plant Abstract Phytosterols (plant sterols and stanols) can lower intestinal cholesterol absorption, but the complex dynamics of the lipid digestion process in the presence of phytosterol esters (PEs) are not fully understood. We performed a clinical experiment in intubated healthy subjects to study the time course of changes in the distribution of all lipid moieties present in duodenal phases during 4 h of digestion of meals with 3.2 g PE (PE meal) or without (control meal) PE. In vitro experiments under simulated gastrointestinal conditions were also performed. The addition of PE did not alter triglyceride (TG) hydrolysis in the duodenum or subsequent chylomicron TG occurrence in the circulation. In contrast, cholesterol accumulation in the duodenum aqueous phase was markedly reduced in the presence of PE ( ؊ 32%, P < 0.10). In vitro experiments confi rmed that PE reduces cholesterol transfer into the aqueous phase. The addition of PE resulted in a markedly reduced presence of meal-derived hepta-deuterated cholesterol in the circulation, i.e., in chylomicrons ( ؊ 43%, PE meal vs. control; P < 0.0001) and plasma ( ؊ 54%, PE meal vs. control; P < 0.0001). The present data show that addition of PE to a meal does not alter TG hydrolysis but displaces cholesterol from the intestinal aqueous phase and lowers chylomicron cholesterol occurrence in humans.
Plant sterols (PS) in foods are subject to thermal oxidation to form PS oxidation products (POP). This study measured POP contents of 19 foods prepared by typical household baking and cooking methods using margarines without (control) and with 7.5% added PS (as 12.5% PS-esters, PS-margarine). Median POP contents per portion size of cooked foods were 0.57 mg (range 0.05-1.11 mg) with control margarine versus 1.42 mg (range 0.08-20.5 mg) with PS-margarine. The oxidation rate of PS (ORP) was 0.50% (median) with the PS-margarine and 3.66% with the control margarine. Using the PS-margarine, microwave-cooked codfish had the lowest POP content, with 0.08 mg per portion, while shallow-fried potatoes had the highest POP content, 20.5 mg per portion. Median POP contents in cookies, muffins, banana bread, and sponge cake baked with the control or PS-margarine were 0.12 mg (range 0.11-0.21 mg) and 0.24 mg (range 0.19-0.60 mg) per portion, with a corresponding ORP of 1.38% and 0.06%, respectively. POP contents in all the cooked and baked foods did not exceed 20.5 mg per typical portion size. A wide variation in the distribution of individual POP among different foods existed, with 7-keto-PS and 5,6-epoxy-PS being the major oxidation products.
The PS-containing drink, which empties fast from the stomach, does not sufficiently trigger gallbladder contraction without co-ingestion of a solid meal and in consequence does not induce the necessary physiological changes needed to allow PS to exhibit their effect on inhibiting cholesterol absorption.
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