Possible adverse effects of frying with vegetable oils.

The question of whether heated fats in the diet may be detrimental to health is nowadays of the upmost concern, but finding an answer is not easy and requires careful consideration of different aspects of lipid oxidation. This review is divided into two sections. The first part deals with the nature of the new compounds formed at high temperature in the frying process as well as their occurrence in the diet while the second part focuses on their possible nutritional and physiological effects. Oxidation products present in abused frying fats and oils are the compounds most suspected of impairing the nutritional properties of the oils or involving adverse physiological effects. The recent studies on their health implications include those related to their fate and those focused on their effects in metabolic pathways and the most prevalent diseases.

A detailed identification study on high-temperature degradation products of oleic and linoleic acid methyl esters by GC-MS and GC-FTIR.

GC-MS and GC-FTIR were complementarily applied to identify oxidation compounds formed under frying conditions in methyl oleate and linoleate heated at 180°C. The study was focused on the compounds that originated through hydroperoxide scission that remain attached to the glyceridic backbone in fats and oils and form part of non-volatile molecules. Twenty-one short-chain esterified compounds, consisting of 8 aldehydes, 3 methyl ketones, 4 primary alcohols, 5 alkanes and 1 furan, were identified. In addition, twenty non-esterified volatile compounds, consisting of alcohols, aldehydes and acids, were also identified as major non-esterified components. Furanoid compounds of 18 carbon atoms formed by a different route were also identified in this study. Overall, the composition of the small fraction originated from hydroperoxide scission provides a clear idea of the complexity of the new compounds formed during thermoxidation and frying.

Heterogeneous aspects of lipid oxidation in dried microencapsulated oils.

This work was aimed at studying lipid oxidation in dried microencapsulated oils (DMOs) during long-term storage. Samples were prepared by freeze-drying of emulsions containing sodium caseinate and lactose as encapsulating components. Evaluation of lipid oxidation was approached by quantitative analysis of nonvolatile lipid oxidation products and tocopherol. Lipid oxidation products were analyzed by separation of polar compounds by adsorption chromatography followed by HPSEC with refraction index detection for quantitation of oxidized triglyceride monomers, dimers, and oligomers. The analytical method applied enabled the detection of different oxidative patterns between the free and encapsulated oil fractions. The free oil fraction of DMOs showed a typical oxidative pattern for oils in continuous phase, which consisted of a clear induction period, in which hydroperoxides (oxidized triglyceride monomers) accumulated, before oxidation accelerated. The end of the induction period was marked by the total loss of tocopherol and the initiation of polymerization. On the contrary, the encapsulated oil showed a pattern characteristic of a mixture of oils with different oxidation status. Thus, high contents of advanced oxidation compounds (polymerization compounds) were detected when the antioxidant (tocopherol) was still present in high amounts. It is concluded that the encapsulated oil was comprised of oil globules with very different oxidation status. The results obtained in this study gave evidence of heterogeneous aspects of lipid oxidation in a dispersed-lipid food system.

Quantitation of short-chain glycerol-bound compounds in thermoxidized and used frying oils. A monitoring study during thermoxidation of olive and sunflower oils.

Major short-chain glycerol-bound compounds were investigated in olive oil (OO) and conventional sunflower oil (SO) during thermoxidation at 180 degrees C for 5, 10, and 15 h. These compounds included methyl heptanoate (C7:0), methyl octanoate (C8:0), methyl 8-oxo-octanoate (8-oxo-C8:0), methyl 9-oxononanoate (9-oxo-C9:0), dimethyl octanodiate (C8:0 diester), and dimethyl nonanodiate (C9:0 diester), which were analyzed by GC after derivatization of triacylglycerols to fatty acid methyl esters. An acceptable linear correlation (r = 0.967) was found between the total content of these compounds and the total content of polar compounds, suggesting that quantitation of the major short-chain glycerol-bound compounds provides a good indication of the total alteration level of oils heated at frying temperature. Samples with levels of polar compounds around 25% on oil showed total contents within 2-3 mg/g of oil. To determine the content of these compounds in used frying oils, 10 samples from restaurants and fried-food outlets in Spain were analyzed. Results showed total levels between 2.13 and 7.56 mg/g of oil in samples with contents of polar compounds ranging from 18.8 to 55.5% on oil. Samples with levels of polar compounds of approximately 25% showed total contents of the short-chain compounds similar to those found in the thermoxidized oils, that is, within 2-3 mg/g of oil.

Formation and evolution of monoepoxy fatty acids in thermoxidized olive and sunflower oils and quantitation in used frying oils from restaurants and fried-food outlets.

The formation and evolution of monoepoxy fatty acids, arising from oleic and linoleic acids, were investigated in olive oil and conventional sunflower oil, representatives of monounsaturated and polyunsaturated oils, respectively, during thermoxidation at 180 degrees C for 5, 10, and 15 h. Six monoepoxy fatty acids, cis-9,10- and trans-9,10-epoxystearate, arising from oleic acid, and cis-9,10-, trans-9,10-, cis-12,13-, and trans-12,13-epoxyoleate, arising from linoleic acid, were analyzed by gas chromatography after oil derivatization to fatty acid methyl esters. Considerable amounts, ranging from 4.29 to 14.24 mg/g of oil in olive oil and from 5.10 to 9.44 mg/g of oil in sunflower oil, were found after the heating periods assayed. Results showed that the monoepoxides quantitated constituted a major group among the oxidized fatty acid monomers formed at high temperature. For similar levels of degradation, higher contents of the monoepoxides were found in olive oil than in sunflower oil. Ten used frying oils from restaurants and fried-food outlets in Spain were analyzed to determine the contents of the monoepoxides in real frying oil samples. Levels ranged from 3.37 to 14.42 mg/g of oil. Results show that, for similar degradation levels, the monoepoxides were more abundant in the monounsaturated oils than in the polyunsaturated oils.

[Physical activity and cardiovascular and metabolic risk factors in general population]. / Actividad física y factores de riesgo cardiovascular y metabólico en la población general.

BACKGROUND AND OBJECTIVE: Our purpose was to evaluate in a cross-section, populational study the association between daily physical activity and various metabolic and cardiovascular disease risk factors. PATIENTS AND METHOD: A total of 1226 randomly selected persons (aged 18-65 years) from a town in southeast Spain were evaluated for studying the association between the level of daily physical activity, both in and out of working hours, and the following variables: body mass index, plasma lipids, hypertension, obesity, altered baseline glycemia, and abnormal glucose tolerance. RESULTS: The intensity of the physical activity at work was related negatively with insulin resistance and levels of LDL cholesterol, and positively with HDL cholesterol. The probability of hypertension, altered baseline glycemia, and abnormal glucose tolerance was greater in those undertaking less daily physical activity. CONCLUSIONS: Daily physical activity, considered as part of the lifestyle, is related with the presence of components of the metabolic syndrome. An increase in daily physical activity should contribute to improve preventible cardiovascular risk factors.

Actividad física y factores de riesgo cardiovascular y metabólico en la población general / Physical activity and cardiovascular and metabolic risk factors in general population

FUNDAMENTO Y OBJETIVO: Evaluar en un estudio poblacional la asociación entre la actividad física diaria y diferentes factores de riesgo metabólico y cardiovascular. PACIENTES Y MÉTODO: En 1.226 personas (edad: 18-65 años) aleatoriamente seleccionadas en una población del sudeste español se ha evaluado la asociación entre el nivel de actividad física diaria laboral y extralaboral con las siguientes variables: índice de masa corporal, lípidos plasmáticos, presencia de hipertensión arterial, obesidad, glucemia basal alterada y tolerancia anormal de la glucosa. RESULTADOS: La intensidad de la actividad física en el trabajo se correlacionó de manera negativa con las concentraciones de colesterol ligado a lipoproteínas de baja densidad y positivamente con las de colesterol ligado a lipoproteínas de alta densidad. La probabilidad de presentar hipertensión arterial, glucemia basal alterada o tolerancia anormal de la glucosa fue mayor en aquellos que tuvieron una menor actividad física diaria. CONCLUSIONES: La actividad física diaria, considerada como uno de los componentes del estilo de vida, se asocia con la presencia de los componentes del síndrome metabólico. Un aumento de la actividad física diaria debe contribuir a mejorar los patrones favorables a la prevención de los factores de riesgo cardiovascular (AU)

Effect of temperature and addition of alpha-tocopherol on the oxidation of trilinolein model systems.

The effects of temperature and addition of alpha-tocopherol were evaluated in trilinolein model systems through quantification of oxidized TAG monomers, dimers, and polymers following oxidation at different temperatures. Samples of trilinolein without and with 250 and 500 mg/kg alpha-tocopherol added were stored at 25, 60, and 100 degrees C. Quantification of oxidized monomers, dimers, and polymers by a combination of adsorption and exclusion chromatography provided a useful measurement for studying the evolution of oxidation. Results showed that the amounts of primary oxidation compounds (trilinolein oxidized monomers) that accumulated during the induction period decreased as the temperature increased, indicating that the slope of the initial linear stage of oxidation depended on temperature. The end of the induction period was marked by a sharp increase in the levels of total oxidation compounds, the initiation of polymerization, and the loss of alpha-tocopherol. Addition of alpha-tocopherol did not prevent, but rather delayed, formation of trilinolein oxidized monomers and the initiation of polymerization.

Oxidized fats in foods.

PURPOSE OF REVIEW: Lipid oxidation is the cause of important deteriorative changes in chemical, sensory and nutritional food properties. In particular, the question of whether oxidized fats in the diet may be detrimental to health is nowadays of the upmost concern, but finding an answer is not easy and requires careful consideration of different aspects of lipid oxidation. RECENT FINDINGS: In this review, the most recent works on the formation, nature and evaluation of oxidized dietary lipids are addressed; important issues such as the difficulties encountered in estimating their intake and the relationships between oxidants and antioxidants in the diet are discussed, and the latest studies on health implications of oxidized lipids are summarized. SUMMARY: The current literature reflects various important points. At present, there is no information on the intake of oxidized fats, which is essential to know if the amount of oxidized lipids in normal diets is sufficient to cause the physiological effects claimed. Recently, relevant advances in analytical methodologies for quantitation of specific oxidation compounds have been reported, although their application to improve the analytical definition of the oxidized substrate used in nutritional studies is still a goal to be reached. Alternatively, one of the most promising current tendencies in this field is the study of the molecular targets by which dietary oxidized lipids can influence health. Overall, more selected research based on coordinated multidisciplinary studies is needed to define the role of dietary oxidized fats in health.