Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160°C, 180°C and 200°C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography–mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160 degrees C, 180 degrees C and 200 degrees C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography-mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Changes in Mean Intake of Fatty Acids and Intake of Saturated and trans Fats from Potatoes: NHANES 2005–2006, 2007–2008, and 2009–2010

Studies have shown that higher than usual intakes of trans fatty acids (TFAs) have adverse effects on blood lipids. Because of this, in 2006 the US FDA mandated labeling of TFAs on food packages. The food and restaurant industries, including the potato industry, reformulated their foods to reduce or eliminate partially hydrogenated vegetable oils and TFAs. Before mandatory labeling, grain-based desserts, yeast breads, and French-fried potatoes (FFPs) were the top sources of TFAs in the food supply; by 2007, potato food manufacturers and quick-service restaurants had reduced or eliminated TFAs without increasing saturated fatty acids (SFAs). FFPs are no longer a source of TFAs in the food supply. This study examined energy and fatty acid intake among children aged 6–11 y, adolescents aged 12–18 y, and adults aged ≥19 y across 3 time periods by using data from the NHANES 2005–2006, 2007–2008, and 2009–2010. On average, intakes of total energy, total fat, SFAs, and monounsaturated fatty acids (MUFAs) decreased significantly between 2005–2006 and 2009–2010 among children and adolescents; however, the intake of polyunsaturated fatty acids (PUFAs) did not change. Among adults, intakes of total fat, SFAs, and MUFAs decreased; however, total energy and PUFA intake did not change. On the day of the 2009–2010 survey, ∼13% of children and 10% of adolescents reported consuming fried FFPs, whereas <7% of adults reported consumption of fried FFPs. Intakes of SFAs and TFAs from fried FFPs decreased significantly between 2005–2006 and 2009–2010 among children, adolescents, and adults. This study confirms that intake of TFAs from FFPs is trivial.     

An update on potato crisps contents of moisture,fat, salt and fatty acids (including trans-fatty acids) with special emphasis on new oils/fats used for frying

Eighteen brands of potato crisps, frequently consumed, were analyzed to establish their nutritional value in relation to salt, fat and fatty acid (FA) composition. The purpose of the present study was to determine moisture, total fat, salt contents and FA profiles (including trans-FAs), and to identify the oil/fat used for frying of the 18 brands of potato crisps. Our results show that salt content ranged from 0.127 to 2.77 g/100 g and total fat content of potato crisps varied between 20.0 and 42.8 g/100 g. With respect to FAs analysis, palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) were the major FAs found in the analyzed potato crisps. It is clear from our work that nowadays most potato crisps are currently produced using oils with high contents in unsaturated FAs, which can be considered as healthier from a nutritional point of view. Nevertheless, some brands of potato crisps still use palm oil or a blend of palm oil and other fats/oils, which are very rich in saturated FAs.     

An assessment of the economic and heart health benefits of replacing saturated fat in the diet with monounsaturates in the form of rapeseed (canola) oil

There is a well‐established requirement for the UK population to reduce the saturates content of its diet from around 13.3% energy (E) intake to 10% E intake (including alcohol) and to improve fat quality by increasing monounsaturated fatty acid (MUFA) intake. Canola (rapeseed) oil is one of the richest sources of dietary MUFAs and is a good source of the omega‐3 polyunsaturated fatty acid (PUFA) alpha‐linolenic acid. Recent advances using conventional plant breeding have led to the development of high‐oleic canola, which has an increased level of MUFA and greater oxidative stability, making it suitable for a wide range of culinary purposes including frying. Around 7% of dietary saturated fatty acid (SFA) intake in adults derives from potatoes (fried potatoes and chips) and savoury snacks, with the value increasing to 13%–15% SFA in 4–18‐year‐olds. Traditionally, frying oils have been high in saturates content and their replacement with lower SFA alternatives provides the opportunity for food manufactures to lower SFA content of food with minimal consumer intervention. It has been estimated that at least half of the SFA in this category of foods can be replaced. In this review of literature, ten intervention studies were identified, where SFAs and/or carbohydrates were replaced by rapeseed oil, and the effect on blood lipids were reported. Results from these studies were pooled using standard meta‐analysis methods. The standard mean differences in total cholesterol (Total‐C) and low‐density lipoprotein cholesterol (LDL‐C) were 0.86 mmol/l [95% confidence interval (CI): ?1.05 to ?0.66] (ten studies) and 0.87 mmol/l (95% CI: ?1.07 to ?0.66) (nine studies), respectively, both significant (P < 0.0001) and non‐heterogeneous (P > 0.1). Using the pooled data, it can be calculated that each gram of SFA intake reduction was associated with reductions in both Total‐C and LDL‐C of 0.03 mmol/l, while each gram increase in either MUFA or PUFA reduced Total‐C by 0.05 and 0.09, respectively, and LDL‐C by 0.04 mmol/l and 0.08 mmol/l, respectively. It was also calculated that each 10 g increase in MUFA or rapeseed oil intake was associated with a reduction in Total‐C of 9.8% and 5.8%, respectively. In 2006, annual direct healthcare costs associated with coronary heart disease were estimated at £3.2 billion and the overall cost to the UK economy was nearly £9.0 billion. Assuming 3.5 g total fat (typically 30% E SFA) is replaced by 3.5 g rapeseed oil, then it can be predicted that Total‐C will be reduced by 1.9%, equivalent to an annual reduction of £61 million direct health costs and £171 million total costs.     

Analysis of the reduction of trans-fatty-acid levels in the foods of Argentina

Abstract

Adverse health effects found to be caused by the industrial trans fatty acids (TFAs) encouraged significant changes in the food supply. A working model was implemented based on a multisectoral approach to monitor progress in the reduction of TFAs in compliance with Argentine food regulations. We analysed the fatty-acid profiles of commercial foods over the entire country comparing the results before and after the deadline for the compliance. A 93% adherence in the foods was obtained after the finalisation of the deadline for the compliance with the limited use of partially hydrogenated vegetable oils. The analytical monitoring was a key tool operating for the compliance by the food manufacturers. The industrial TFAs were mostly replaced by semisolid fractions of vegetable oils containing high percentages of saturated fatty acids. Promising innovations for the food industry were established that provided more healthful alternative substitutes for TFAs.     

Prolonged consumption of trans fat favors the development of orofacial dyskinesia and anxiety-like symptoms in older rats

Polyunsaturated fatty acids (FAs) are cell membrane components involved in brain functions. We hypothesized that long-term trans fat consumption is able to modify the membrane FAs composition impairing behavioral parameters related to aging. In this study, a comparison of behavioral parameters at 10 and 15 months of trans fat consumption by male Wistar rats was made. Animals were fed for 10 and 15 months from weaning with diets containing either 20% w/w soybean oil (SO), rich in n-6 PUFA, hydrogenated vegetable fat (HVF), rich in trans FAs, or a standard diet (control – C). At both evaluation times, HVF-fed rats showed progressively increased parameters of orofacial dyskinesia, fear and anxiety-like symptoms. The HVF diet reduced locomotor and exploratory activities progressively over 10 and 15 months of supplementation, while the standard and SO diets did not. In this study, we showed that chronic trans FAs consumption from weaning is able to favor the development of neuromotor and neuropsychiatric diseases, whose intensity was time dependent.     

Effects of a normolipidic diet containing trans fatty acids during perinatal period on the growth, hippocampus fatty acid profile, and memory of young rats according to sex

ObjectiveTo investigate whether dietary trans fatty acids (TFAs) are incorporated in the hippocampus and its effects on the growth and aversive and spatial memories of young rats.MethodsWistar rat offspring whose mothers were fed with normolipidic diets containing soybean oil (soy group) or hydrogenated vegetable oil (trans group) during gestation and lactation were used. Male and female pups received the same diets as their mothers until the end of behavioral testing. The composition of fatty acids in the total lipids of the diets and hippocampus was quantified by gas chromatography. The results were evaluated by Student’s t test or analysis of variance followed by the Bonferroni correction.ResultsThe trans male and female body weights were higher during lactation and after weaning, with trans males having the lower body weight of the two. There was incorporation of 0.11% and 0.17% of TFAs in the hippocampi of male and female rats, respectively. During passive avoidance test, there was no significant difference. In the water maze test, there was no significant difference between male groups in the training and retention phases, except on day 4, when there was a significant decrease in latency in trans males. Trans females were worse on day 2 only and showed an improvement in spatial memory during the probe trial.ConclusionThe TFAs were incorporated in small amounts in the hippocampus and did not affect aversive memory. However, spatial memory was modified in young rats fed with a diet rich in TFAs. These findings suggested that, in addition to the TFA content of the diet provided, it is important to consider the provision of essential fatty acids and the ω-6/ω-3 ratio.     

Consumption of Oxidized and Partially Hydrogenated Oils Differentially Induces Trans-Fatty Acids Incorporation in Rats' Heart and Dyslipidemia

Objectives: A direct effect of process-induced trans-fatty acids (TFAs) on nonalcoholic fatty liver disease (NAFLD) as a cardiovascular disease (CVD) risk factor has previously been shown. We hypothesized that TFAs directly induced CVD. This article describes an investigation of the association between TFAs, provided by the consumption of oxidized soybean oil and margarine, and plasma lipid profiles, coronary artery lesions, and coronary fatty acids distribution in rats. Male rats were fed a standard chow or high-fat diet containing different TFA levels ranging from <1%, <2%, and >2% of total fat in fresh soybean oil, oxidized soybean oil, and margarine, respectively, for 4 weeks.

Results: The results indicated that the high-fat diets differently changed the plasma lipid profiles by significantlt increasing triglycerides, total cholesterol, low-density lipoprotein cholesterol, and the ratio of low-density to high-density lipoprotein cholesterol compared to control rats. Compared to fresh soybean oil, oxidized oil further increased plasma lipid markers. The strongest inflammatory effect was induced by margarine, which contains the highest level of TFAs, or 2% of total fat. Total TFAs in the heart of the margarine-fed group were increased by 4.7 regarding to control and by 2.17 and 2.6 relative to groups receiving oxidized and fresh oil, respectively. Increased TFAs consumption was associated with increased histological aspects of atherosclerotic lesions in a dose-dependent manner.

Conclusion: In conclusion, process-induced TFAs cause changes including proatherogenic plasma lipid markers, heart fatty acid profiles, and coronary artery histology depending on the TFA level in the supplemented fat and therefore on the type of technological process used.     

An update on potato crisps contents of moisture, fat, salt and fatty acids (including trans-fatty acids) with special emphasis on new oils/fats used for frying

Eighteen brands of potato crisps, frequently consumed, were analyzed to establish their nutritional value in relation to salt, fat and fatty acid (FA) composition. The purpose of the present study was to determine moisture, total fat, salt contents and FA profiles (including trans-FAs), and to identify the oil/fat used for frying of the 18 brands of potato crisps. Our results show that salt content ranged from 0.127 to 2.77?g/100?g and total fat content of potato crisps varied between 20.0 and 42.8?g/100?g. With respect to FAs analysis, palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) were the major FAs found in the analyzed potato crisps. It is clear from our work that nowadays most potato crisps are currently produced using oils with high contents in unsaturated FAs, which can be considered as healthier from a nutritional point of view. Nevertheless, some brands of potato crisps still use palm oil or a blend of palm oil and other fats/oils, which are very rich in saturated FAs.     

Impact of diets containing corn oil or olive/sunflower oil mixture on the human plasma and lipoprotein lipid metabolism

Summary Background The effects of monounsaturated fatty acids (MUFA) rich diets compared to those that are rich in polyunsaturated fatty acids (PUFA) as well as the effects of an intake of single oils compared to oil mixtures are controversially discussed and results are contradictory. Aim of this study To evaluate the effects of a plant oil-mixture (olive/sunflower oil; saturated/monounsaturated/polyunsaturated (S/M/P) = 14:69:17) high in oleic acid but also showing a moderate content of polyunsaturated fatty acids (PUFA) in comparison with a single, PUFA rich corn oil (S/M/P = 13:33:54) used in a normal, balanced diet on human plasma and lipoprotein metabolism. Methods The double-blind designed study comprised 28 healthy, non-smoking young men aged between 19 and 31 years. After two weeks of adjustment (mixed, balanced diet: 11.6 MJ average, average fat intake ∼105 g/d), the design included a two week test period in which a diet with 80 g corn oil/d vs a mixture of 68 g olive- and 12 g sunflower oil/d (total 80 g) as the main fat source was given, followed by a crossover after two weeks. Compliance and ingestion of diets were monitored by assessing the fatty acid pattern in LDL and by determination of α- and γ-tocopherol in plasma and LDL. Results Diets were well incorporated due to the significant changes in plasma- and LDL-tocopherol levels and the significant different average ratio of oleic acid to linoleic acid in LDL. The PUFA-rich corn oil diet was able to reduce low density lipoprotein (LDL) cholesterol from adjustment to T2 significantly (p < 0.01), which was also confirmed by a trend after cross over (p=0.15). Total cholesterol (only after cross over at T3), total triglycerides (TG) and very low density lipoprotein (VLDL)-TG were significantly lower at T2 after the corn oil diet than after the mixed oil diet. Total high density lipoproteins (HDL) and HDL cholesterol remained unchanged by both diets. Conclusions The results show that during the intervention of two weeks for each diet and the following cross over the corn oil diet had more influence on lipoprotein metabolism than the MUFA-rich diet. The hypocholesteremic effect of the PUFA-rich diet must also be connected with the high amount of unsaponifiable substances, mainly phytosterols in the corn oil. Received: 10 May 2001, Accepted: 17 September 2001     

Lipid Profiles and trans Fatty Acids in Serum Phospholipids of Semi-nomadic Fulani in Northern Nigeria

The Fulani are semi-nomadic pastoralists of West Africa whose diet, culture, and economy are centred on cattle. Previous studies have shown that the Fulani of northern Nigeria derive 50% of their total calories from fat and 30% of their calories from milk, cheese, yogurt, and butter oil that contain significant amounts of trans fatty acids (TFAs), primarily vaccenic acid, which raise total serum cholesterol and low-density lipoprotein-cholesterol (LDL-C), and lower high-density lipoprotein-cholesterol (HDL-C). The study was conducted to know how the consumption of relatively large amounts of dairy products by adult Fulani affected the TFA content of their serum phospholipids. Blood samples were collected from 22 male and 29 female Fulani, aged 35–60 years, who were living in rural areas of Gombe state in northeastern Nigeria. The total serum phospholipid fraction was isolated, and its fatty acid composition was determined. Surprisingly, vaccenic acid was not detected, and three other TFAs—18:1-t6, 18:1-t9, and 18:2-t9, t12—together accounted for only 0.16% of the total fatty acid. The mean serum total cholesterol, LDL-C, and triglyceride concentrations of the subjects were within the normal range for populations in developed countries; however, at 32 mg/dL, the mean serum HDL-C concentration of the Fulani males was slightly below the lower limit of the reference range. No correlations were observed between the total TFA percentage or that of the three individual TFAs and any of the parameters of the serum lipid profile. These findings indicate that, with respect to TFAs at least, the fatty acid pattern of the serum phospholipids of Fulani pastoralists does not reflect the high TFA content of their traditional diet. Despite the consumption of rumenic acid-rich dairy products, for unknown reasons, the semi-nomadic Fulani manage to maintain a low level of TFAs in their blood and a relatively healthful serum lipid profile. While the mechanism that accounts for this disconnect between the consumption of TFAs by Fulani pastoralists and the proportion of TFAs in their serum phospholipids is obscure, possibilities include discrimination against rumenic acid during the process of triglyceride synthesis and chylomicron synthesis in the intestine and the preferential oxidation of TFAs by Fulani the people compared to other ethnic groups.Key words: Lipid profile, Fulani, Serum, Trans fatty acids, Nigeria     

Conjugated linoleic acid (CLA): Good or bad trans fat?

Even though trans fatty acids (TFAs) are present in natural sources such as foods from ruminant origins, the development of partially hydrogenated vegetable oil contributed to a significant increase in total TFAs consumption in humans. Currently, TFA consumption is considered to be a risk factor for coronary heart diseases. Researchers are now starting to discover that not all TFAs behave in a similar manner, that is, isomer specificity may be found. Among non-conjugated TFAs, plant originated TFAs (mainly elaidic and linolelaidic acids) are particularly linked to increased risk for coronary heart diseases, while animal originated TFAs (mainly vaccenic acid) are not. Among conjugated TFAs, two major isomers of conjugated linoleic acid (CLA), cis-9,trans-11 and trans-10,cis-12, show distinctive biological activities. A number of clinical trials of CLA with effects on body composition have been reported, but effects on coronary heart disease risk factors have been inconsistent. Meanwhile, safety concerns regarding CLA, in particular isomer specificity, have also been raised. Thus, it is critical to identify isomer specific effects of TFAs on particular risk factors, to determine their health impact.     

The Fatty Acid Species and Quantity Consumed by the Breastfed Infant Are Important for Growth and Development

The fatty acids (FAs) of human milk (HM) are the building blocks of the HM lipidome, contributing to infant health and development; however, this has not been comprehensively characterised with respect to infant intake. Eighteen Western Australian mother–infant dyads provided monthly longitudinal HM samples during six months of exclusive breastfeeding. Monthly anthropometric measurements, health data and basic maternal food frequency data were also collected. At three months, infant 24 h milk intake and total lipid intake were measured. The FA profile was analysed using gas chromatography–mass spectrometry. Linear regression and Pearson’s correlation were used to identify associations between HM FA composition, HM FA intake, maternal characteristics and infant growth and developmental outcomes. Mean infant intake of total lipids was 29.7 ± 9.4 g/day. HM FA composition exhibited wide variation between dyads and throughout lactation. Infant intake of a number of FAs, including C15:0, C18:1, C18:2 and C20:3, was positively related to infant growth (all p < 0.001). There were no relationships detected between C22:5 and C20:5 and infant head circumference. Infant total lipid intake and the infant intake of many FAs play essential roles in infant growth and development. This study highlights the important relationships of many HM FAs not previously described, including C15:0 and C18:2 species. Infant outcomes should be considered in the context of intake in future HM studies.     

Accumulation of fatty acids in purslane grown in hydroponic salt stress conditions

Purslane (Portulaca oleracea L.) is the eighth most common plant distributed throughout the world being a heat- and drought-tolerant plant. In this study, we evaluated the effect of salinity on total amounts of fatty acids (FAs) and ω3/ω6 ratio in leaves of purslane. Plants exposed to four levels of chloride salinity in the root zone (60, 90, 120 and 240 mM NaCl) for 40 days showed no signs of toxicity or death. The main FAs detected were C16:0>C18:3>C18:2. The ratio of ω6 to ω3 was not changed with salt stress. Hierarchic cluster analysis brought together 60 and 90 mM NaCl in control plants, based on their FA content. The results of this study confirm the purslane as a plant rich in FAs whose consumption may contribute to dietary intake of ω3 polyunsaturated fatty acid, with obvious benefits to human health.     

TransFatty Acid Content of Selected New Zealand Foods

The fatty acid composition andtransfatty acid content of samples of New Zealand foods representing certain food groups have been determined by a combined gas chromatography/infrared spectroscopy method. The mean levels oftransfatty acids in the fat portion of these foods are (g/100 g fatty acids) margarine, 16.4; table spreads, 15.7; butter/margarine blends, 9.6; butter, 6.4; pastry, 6.2; potato chips (deep fried in beef dripping), 5.6; cakes, 5.3, crackers, 2.0; sweet biscuits, 1.9; potato crisps, 0.5. Expressed as a proportion of dry weight of food the meantransfatty acid content values are (g/100 g dry weight) margarine, 14.9; table spreads, 14.4; butter/margarine blends, 8.1; butter, 6.0; potato chips (deep fried in beef dripping), 1.6; pastry, 1.2; cakes, 0.9, crackers, 0.3; sweet biscuits, 0.2; potato crisps, 0.2. In contrast to North America, hydrogenated plant oils with high levels oftransfatty acids do not appear to be present in the New Zealand food supply.     

Nonhydrogenated cottonseed oil can be used as a deep fat frying medium to reduce trans-fatty acid content in french fries

OBJECTIVE: The purpose of this research study was to evaluate the fatty acid profile, in particular trans-fatty acids, of french fries fried in nonhydrogenated cottonseed oil as compared with french fries fried in partially hydrogenated canola oil and french fries fried in partially hydrogenated soybean oil. DESIGN: Cottonseed oil, partially hydrogenated canola oil, and partially hydrogenated soybean oil were subjected to a temperature of 177 degrees C for 8 hours per day, and six batches of french fries were fried per day for 5 consecutive days. French fries were weighed before frying, cooked for 5 minutes, allowed to drain, and reweighed. Oil was not replenished and was filtered once per day. Both the oil and the french fries were evaluated to determine fatty acid profiles, trans-fatty acids, and crude fat. STATISTICAL ANALYSIS: A randomized block design with split plot was used to analyze the data collected. Least-squares difference was used as the means separation test. RESULTS: No significant differences were found between fries prepared in the three oil types for crude fat. Fatty acid profiles for the french fries remained stable. The french fries prepared in cottonseed oil were significantly lower in trans-fatty acids. The combined total of the trans-fatty acid content and saturated fatty acid content were lower in french fries prepared in cottonseed oil. CONCLUSIONS: Because deep fat frying remains a popular cooking technique, health professionals should educate the public and the food service industry on the benefits of using nonhydrogenated cottonseed oil as an alternative to the commonly used hydrogenated oils.     

Nutrient losses and gains during frying: a review

Recent consumer interest in ‘healthy eating’ has raised awareness to limit the consumption of fat and fatty foods. What are the relative nutritional advantages and disadvantages of consuming fried foods? Are all fried foods bad for you? A review on macro-and micronutrients losses and gains during frying is presented here. Frying has little or no impact on the protein or mineral content of fried food, whereas the dietary fibre content of potatoes is increased after frying due to the formation of resistant starch. Moreover, the high temperature and short transit time of the frying process cause less loss of heat labile vitamins than other types of cooking. For example, vitamin C concentrations of French fried potatoes are as high as in raw potatoes, and thiamine is well retained in fried potato products as well as in fried pork meat. The nutritive value of the frying media is also important to take into consideration and therefore losses of nutrients from the frying oil are also discussed. Although some unsaturated fatty acids and antioxidant vitamins are lost due to oxidation, fried foods are generally a good source of vitamin E. It is true that some fat is inevitably taken up by the food being fried, contributing to an increased energy density. However, this also results in highly palatable foods with a high nutritional content. It is concluded that fried foods certainly have a place in our diets.     

Chemopreventive Effects of Dietary Canola Oil on Colon Cancer Development

Fatty acid composition of dietary fat plays a vital role in colon tumor development in animal models. Fats containing ω-6 fatty acids (e.g., corn oil) enhanced and ω-3 fatty acids (e.g., flaxseed oil) reduced chemically induced colon tumor development in rats. The objective of the present investigation was to study the effects of dietary canola oil, a source of ω-3 fatty acid on azoxymethane-induced colon cancer development in Fischer rats and compare with dietary corn oil.

Dietary canola oil significantly (P < 0.05) decreased colonic tumor incidence and tumor multiplicity as compared to dietary corn oil in rats. Fatty acid analysis showed that corn oil group had higher levels of ω-6 fatty acid levels, whereas the canola oil groups exhibited higher levels of ω-3 fatty acids from the colon and serum samples of rats. For the mechanistic study, COX-2 expression in the colon samples from the canola oil group was significantly lower (P < 0.05) as compared to the corn oil group.

Taken together, dietary canola oil may be chemopreventive for colon tumor development in Fischer rats as compared to possibly by increasing ω-3 fatty acid levels and decreasing COX-2 levels.     

Effects of n-3 fatty acids in subjects with type 2 diabetes: reduction of insulin sensitivity and time-dependent alteration from carbohydrate to fat oxidation

BACKGROUND: Effects of fish oil supplements on metabolic variables are insufficiently clarified in type 2 diabetes. OBJECTIVE: We aimed to investigate short-term (1 wk) and longer-term (9 wk) effects of n-3 fatty acids. DESIGN: Twenty-six subjects with type 2 diabetes without hypertriacylglycerolemia participated in a double-blind controlled study. Median intake in the intervention group was 17.6 mL fish oil/d (1.8 g 20:5n-3, 3.0 g 22:6n-3, and 5.9 g total n-3 fatty acids). The control group received 17.8 mL corn oil/d (8.5 g 18:2n-6). RESULTS: Plasma phospholipid 20:5n-3 and 22:6n-3 increased, whereas 18:2n-6 decreased, in the fish oil group compared with the corn oil group after 1 wk. The two n-3 fatty acids also increased in adipose tissue biopsy samples taken after 9 wk in the fish oil group. Glucose concentrations (home-monitored) were approximately 1 mmol/L higher in the fish oil group than in the corn oil group at the end of the intervention (P = 0.035). Glucose utilization measured by using an isoglycemic clamp was lowered in the fish oil group compared with that in the corn oil group at the end of the intervention (P = 0.049), whereas glucagon-stimulated C-peptide tended to increase (P = 0.078). The fish oil group utilized less fat for oxidation after 1 wk, with a change to more fat and less carbohydrate oxidation after 9 wk (P = 0.040), than did the corn oil group. CONCLUSION: A high intake of fish oil moderately increases blood glucose and decreases insulin sensitivity in persons with type 2 diabetes without hypertriacylglycerolemia and alters carbohydrate and fat utilization in a time-dependent manner.