Do trans fatty acids from industrially produced sources and from natural sources have the same effect on cardiovascular disease risk factors in healthy subjects? Results of the trans Fatty Acids Collaboration (TRANSFACT) study

Consumption of industrial and ruminant trans fatty acids and risk of coronary heart disease: a systematic review and meta-analysis of cohort studies

The aim of this systematic review and meta-analysis was to summarize the evidence from observational studies assessing the association between intake of trans fatty acids (TFA) and the risk of coronary heart disease (CHD), with a specific emphasis on distinguishing between TFA of industrial and ruminant origin. By searching five bibliographic databases, analyses from six published and two unpublished prospective cohort studies, assessing the association of intake of TFA with fatal and/or non-fatal CHD, were identified. Four and three studies reported separate associations for intake of ruminant or industrial-TFA, respectively. The pooled relative risk estimates for comparison of extreme quintiles of total-TFA intake (corresponding to intake increments ranging from 2.8 to ∼10 g/day) were 1.22 (95% confidence interval: 1.08-1.38; P=0.002) for CHD events and 1.24 (1.07-1.43; P=0.003) for fatal CHD. Ruminant-TFA intake (increments ranging from 0.5 to 1.9 g/day) was not significantly associated with risk of CHD (risk ratio (RR)=0.92 (0.76-1.11); P=0.36), and neither was industrial-TFA intake, although there was a trend towards a positive association (RR=1.21 (0.97-1.50); P=0.09). In conclusion, our analysis suggests that industrial-TFA may be positively related to CHD, whereas ruminant-TFA is not, but the limited number of available studies prohibits any firm conclusions concerning whether the source of TFA is important. The null association of ruminant-TFA with CHD risk may be due to lower intake levels.

Dairy consumption and 10-y total and cardiovascular mortality: a prospective cohort study in the Netherlands

BACKGROUND

The consumption of dairy products (milk, cheese, and butter) has been positively associated with the risk of ischemic heart disease (IHD), stroke, and total mortality because of the saturated fat content of these products; and protective effects against these outcomes have been attributed to the calcium content and low-fat choices of dairy products. However, robust evidence on the net effect of dairy product consumption on mortality is limited.

OBJECTIVE

The objective was to investigate the association between dairy product consumption and the risk of death (from all causes, IHD, and stroke) in the Netherlands Cohort Study (NLCS).

DESIGN

The NLCS was initiated in 120,852 men and women aged 55-69 y at baseline in 1986. After 10 y of follow-up, 16,136 subjects with complete dietary information had died. Twenty-nine percent (men) and 22% (women) of these deaths were due to IHD or stroke. The validated 150-item food-frequency questionnaire provided detailed information on dairy products.

RESULTS

Multivariate survival analyses following a case-cohort approach showed only a few statistically significant, but mostly weak, associations. A slightly increased risk of all-cause and IHD mortality was found for both butter and dairy fat intake (per 10 g/d; rate ratio(mortality): 1.04; 95% CI: 1.01, 1.06) only in women. Fermented full-fat milk was inversely associated with all-cause and nonsignificantly with stroke mortality in both sexes.

CONCLUSIONS

The role of dairy product consumption in mortality generally appeared to be neutral in men. In women, dairy fat intake was associated with slightly increased all-cause and IHD mortality. More research is warranted on a possible protective effect of fermented milk on stroke mortality.

Ruminant and industrial sources of trans-fat and cardiovascular and diabetic diseases

The various positional isomers of oleic acid (18 : 1Δ9c or 9c-18 : 1) may have distinct biological effects. Detrimental effects of consumption of industrial trans-fatty acids (TFA) (elaidic acid; 18 : 1Δ9t) from partially hydrogenated vegetable oils on CVD risk factors are well documented. In addition, epidemiological data suggest that chronic consumption of industrial sources of TFA could alter insulin sensitivity and predispose for type 2 diabetes. However, intervention studies on this issue have remained inconclusive. Moreover, very little information is available on the effect of natural sources of TFA (vaccenic acid; 18 : 1Δ11t) coming from dairy products and ruminant meat on the development of CVD and type 2 diabetes. The review focuses on the impact of the consumption of ruminant TFA in relation to cardiovascular risk factors, inflammation and type 2 diabetes.

Effect of trans fatty acid intake on abdominal and liver fat deposition and blood lipids: a randomized trial in overweight postmenopausal women

Background:

Intake of industrially produced trans fatty acids (TFAs) is, according to observational studies, associated with an increased risk of cardiovascular disease, but the causal mechanisms have not been fully elucidated. Besides inducing dyslipidemia, TFA intake is suspected to promote abdominal and liver fat deposition.

Objective:

We examined the effect of a high intake of TFA as part of an isocaloric diet on whole-body, abdominal and hepatic fat deposition, and blood lipids in postmenopausal women.

Methods:

In a 16-week double-blind parallel intervention study, 52 healthy overweight postmenopausal women were randomized to receive either partially hydrogenated soybean oil providing 15.7 g day⁻¹ of TFA or a control oil with mainly oleic and palmitic acid. Before and after the intervention, body composition was assessed by dual-energy X-ray absorptiometry, abdominal fat by magnetic resonance (MR) imaging, and liver fat by ¹H MR spectroscopy.

Results:

Compared with the control fat, TFA intake decreased plasma high-density lipoprotein (HDL)-cholesterol by 10%, increased low-density lipoprotein (LDL)-cholesterol by 18% and resulted in an increased LDL/HDL-cholesterol ratio (baseline adjusted mean (95% CI) difference between diet groups 0.41 (0.22; 0.60); P<0.001). TFA tended to increase the body fat (0.46 (−0.20; 1.17) kg; P=0.16) and waist circumference (1.1 (−0.1; 2.4) cm; P=0.08) more than the control fat, whereas neither abdominal nor liver fat deposition was affected by TFA.

Conclusion:

The adverse effect of dietary TFA on cardiovascular disease risk involves induction of dyslipidemia, and perhaps body fat, whereas weight gain-independent accumulation of ectopic fat could not be identified as a contributory factor during short-term intake.

Modulation of lipid-induced ER stress by fatty acid shape

Exposure of pancreatic β cells to long-chain saturated fatty acids (SFA) induces a so-called endoplasmic reticulum (ER) stress that can ultimately lead to cell death. This process is believed to participate in insulin deficiency associated with type 2 diabetes, via a decrease in β-cell mass. By contrast, some unsaturated fatty acid species appear less toxic to the cells and can even alleviate SFA-induced ER stress. In the present study, we took advantage of a simple yeast-based model, which brings together most of the trademarks of lipotoxicity in human cells, to screen fatty acids of various structures for their capacity to counter ER stress. Here we demonstrate that the tendency of a free fatty acid (FFA) to reduce SFA toxicity depends on a complex conjunction of parameters, including chain length, level of unsaturation, position of the double bonds and nature of the isomers (cis or trans). Interestingly, potent FFA act as building blocks for phospholipid synthesis and help to restore an optimal membrane organization, compatible with ER function and normal protein trafficking.

Enhancing fatty acid composition of milk and meat through animal feeding

In ruminants, extensive ruminal biohydrogenation of unsaturated fatty acids (FA) results in numerous cis and trans isomers of 18:1 and of conjugated and non-conjugated 18:2, the incorporation of which into ruminant products depends on the composition of the diet (forage vs concentrate) and of dietary lipid supplements. The low amount of 18:3n-3 (α-linolenic acid) absorbed explains its limited incorporation in meat and milk lipids. Its protection against hydrogenation has been an objective for several decades, but only encapsulation in a protein matrix is efficient. In non-ruminants, the FA composition of products is determined by dietary FA, despite minor differences in digestibility and in metabolic activity. Physicochemical differences in intestinal absorption processes between ruminants and non-ruminants can explain the lower FA digestibility in non-ruminants, especially for saturated FA. Unlike in non-ruminants, FA digestibility in ruminants does not depend on FA intake, except for 18:0. The decrease in cow butterfat, especially with concentrate diets, is generally attributed to t10–18:1 or t10,c12–18:2, but the regulation is probably more complex. Differences in terms of butterfat content and FA composition of milk between cow, ewe and goat responses to the amount and composition of ingested lipids are due to between-species variations in mammary metabolism. In animals bred for meat production, dietary 18:3n-3 results in increases in this FA and in n-3 long-chain polyunsaturated FA (20:5n-3, 22:5n-3) in muscles. The extent of this increase depends both on animal and nutritional factors. Grass is a source of 18:3n-3, which contributes to increased 18:3n-3 in muscle of ruminants as well as of pigs. Conjugated linoleic acids are mainly present in fat tissues and milk due to t11–18:1 desaturation. Their concentration depends on tissue type and on animal species. Non-ruminants fed synthetic conjugated linoleic acids incorporate them in significant amounts in muscle, depending on the isomer. All dietary manipulations favouring polyunsaturated FA incorporation in milk and meat lipids increase the risk of lipoperoxidation, which can be efficiently prevented by use of dietary combined hydro- and lipophilic antioxidants in the diet. Putative effects on organoleptic and technological quality of products deserve further studies.

Trans-palmitoleic acid, metabolic risk factors, and new-onset diabetes in U.S. adults: a cohort study

BACKGROUND

Palmitoleic acid (cis-16:1n-7), which is produced by endogenous fat synthesis, has been linked to both beneficial and deleterious metabolic effects, potentially confounded by diverse determinants and tissue sources of endogenous production. Trans-palmitoleate (trans-16:1n-7) represents a distinctly exogenous source of 16:1n-7, unconfounded by endogenous synthesis or its determinants, that may be uniquely informative.

OBJECTIVE

To investigate whether circulating trans-palmitoleate is independently related to lower metabolic risk and incident type 2 diabetes.

DESIGN

Prospective cohort study from 1992 to 2006.

SETTING

Four U.S. communities.

PATIENTS

3736 adults in the Cardiovascular Health Study.

MEASUREMENTS

Anthropometric characteristics and levels of plasma phospholipid fatty acids, blood lipids, inflammatory markers, and glucose-insulin measured at baseline in 1992 and dietary habits measured 3 years earlier. Multivariate-adjusted models were used to investigate how demographic, clinical, and lifestyle factors independently related to plasma phospholipid trans-palmitoleate; how trans-palmitoleate related to major metabolic risk factors; and how trans-palmitoleate related to new-onset diabetes (304 incident cases). Findings were validated for metabolic risk factors in an independent cohort of 327 women.

RESULTS

In multivariate analyses, whole-fat dairy consumption was most strongly associated with higher trans-palmitoleate levels. Higher trans-palmitoleate levels were associated with slightly lower adiposity and, independently, with higher high-density lipoprotein cholesterol levels (1.9% across quintiles; P = 0.040), lower triglyceride levels (-19.0%; P < 0.001), a lower total cholesterol-HDL cholesterol ratio (-4.7%; P < 0.001), lower C-reactive protein levels (-13.8%; P = 0.05), and lower insulin resistance (-16.7%, P < 0.001). Trans-palmitoleate was also associated with a substantially lower incidence of diabetes, with multivariate hazard ratios of 0.41 (95% CI, 0.27 to 0.64) and 0.38 (CI, 0.24 to 0.62) in quintiles 4 and 5 versus quintile 1 (P for trend < 0.001). Findings were independent of estimated dairy consumption or other fatty acid dairy biomarkers. Protective associations with metabolic risk factors were confirmed in the validation cohort.

LIMITATION

Results could be affected by measurement error or residual confounding.

CONCLUSION

Circulating trans-palmitoleate is associated with lower insulin resistance, presence of atherogenic dyslipidemia, and incident diabetes. Our findings may explain previously observed metabolic benefits of dairy consumption and support the need for detailed further experimental and clinical investigation.

PRIMARY FUNDING SOURCE

National Heart, Lung, and Blood Institute and National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.

Ruminant-produced trans-fatty acids raise plasma total and small HDL particle concentrations in male Hartley guinea pigs

Although trans-fatty acid (tFA) intake has been positively associated with coronary heart disease (CHD), the relative effect of consuming industrially produced (IP)- compared with ruminant-produced (RP)-tFA on CHD risk factors is unclear. This study was designed to examine the effects of feeding partially hydrogenated vegetable oil (PHVO), IP-tFA source, and butter oil (BO), RP-tFA source, on the development of atherosclerosis and risk factors associated with CHD. Forty-eight male Hartley guinea pigs were fed a hypercholesterolemic diet containing (9% by weight) PHVO, BO, coconut oil (CO; positive control), or soybean oil (SO; negative control) for 8 or 12 wk (n = 6/group). Morphological analysis revealed that none of the groups developed atherosclerosis. Plasma and hepatic lipids did not differ between the tFA groups, but total and small HDL particles were significantly higher in the BO group than in the PHVO group and mean HDL particle size was significantly smaller in the BO group than in the PHVO group. Compared with the other treatment groups, the SO treatment resulted in significantly lower total cholesterol (TC) and LDL cholesterol in plasma, whereas hepatic TC was significantly higher in the SO group than in the other treatment groups. Plasma and hepatic cholesterol concentrations did not differ between the tFA and CO treatments. These results demonstrate that when fed at a high dose, IP- and RP-tFA had the same effect on established CHD risk factors in male Hartley guinea pigs. The effects of RP-tFA on HDL particle sizes and concentrations warrant further investigation.

An α-linolenic acid-rich formula reduces oxidative stress and inflammation by regulating NF-κB in rats with TNBS-induced colitis

We have previously shown that α-linolenic acid (ALA), a (n-3) PUFA exerts in vitro antiinflammatory effects in the intestine. In this study, we aimed to evaluate its effect on inflammatory and oxidative stress in a colitis model. Colitis was induced in 2 groups at d 0 by intrarectal injection of 2-4-6-trinitrobenzen sulfonic acid (TNBS), whereas the control group received the vehicle. Rats we fed 450 mg . kg(-1) . d(-1) of ALA (TNBS+ALA) while the other colitic group (TNBS) and the control group were fed an isocaloric corn oil formula for 14 d (from d -7 to d 7). RBC fatty acid composition was assessed. Oxidative stress was studied by measuring urinary 8-isoprostanes (8-IP) and colon glutathione (GSH) concentration and inducible nitric oxide synthase (iNOS) expression. Colitis was assessed histologically, by production of proinflammatory mediators, including cytokines, leukotrienes B(4) (LTB(4)), and cyclooxygenase-2 (COX-2) and by nuclear factor-κB (NF-κB) activation. The ALA-rich diet significantly increased the RBC levels of ALA, eicosapentaenoic acid, and docosapentaenoic acid (n-3) compared with the TNBS group (P < 0.01 for all). The beneficial effect of ALA supplementation on oxidative stress was reflected by lower urinary 8-IP levels (P < 0.05), a normalized colon GSH concentration (P < 0.01), and reduced colon iNOS expression (P < 0.05) compared with the TNBS group. ALA also protected against colon inflammation as assessed by lower tumor necrosis factor-α secretion and mRNA level (P < 0.05), reduced NF-κB activation (P = 0.01), and lower colon lipid mediator concentrations such as LTB(4) and COX-2 (P < 0.05) compared with the TNBS group. These findings show that an ALA-rich formula is beneficial to TNBS-induced colitic rats via inhibition of oxidative and inflammatory stress.

Dairy products and plasma cholesterol levels

Cholesterol synthesized in the body or ingested is an essential lipid component for human survival from our earliest life. Newborns ingest about 3-4 times the amount per body weight through mother's milk compared to the dietary intake of adults. A birth level of 1.7 mmol/L plasma total cholesterol will increase to 4-4.5 mmol/L during the nursing period and continue to increase from adulthood around 40% throughout life. Coronary artery disease and other metabolic disorders are strongly associated with low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol as well as triacylglycerol concentration. Milk fat contains a broad range of fatty acids and some have a negative impact on the cholesterol rich lipoproteins. The saturated fatty acids (SFAs), such as palmitic acid (C16:0), myristic acid (C14:0), and lauric acid (C12:0), increase total plasma cholesterol, especially LDL, and constitute 11.3 g/L of bovine milk, which is 44.8% of total fatty acid in milk fat. Replacement of dairy SFA and trans-fatty acids with polyunsaturated fatty acids decreases plasma cholesterol, especially LDL cholesterol, and is associated with a reduced risk of cardiovascular disease. Available data shows different effects on lipoproteins for different dairy products and there is uncertainty as to the impact a reasonable intake amount of dairy items has on cardiovascular risk. The aim of this review is to elucidate the effect of milk components and dairy products on total cholesterol, LDL, HDL, and the LDL/HDL quotients. Based on eight recent randomized control trials of parallel or cross-over design and recent reviews it can be concluded that replacement of saturated fat mainly (but not exclusively) derived from high-fat dairy products with low-fat dairy products lowers LDL/HDL cholesterol and total/HDL cholesterol ratios. Whey, dairy fractions enriched in polar lipids, and techniques such as fermentation, or fortification of cows feeding can be used to produce dairy products with more beneficial effects on plasma lipid profile.

Dietary fatty acids, luminal modifiers, and risk of colorectal cancer

Inconsistent observations in epidemiologic studies on the association between total fat intake and colorectal cancer may be ascribed to opposing effects of individual fatty acids and the presence of other dietary constituents that modify luminal or systemic lipid exposure. We analyzed the data from a population-based case-control study that included 1,163 cases and 1,501 controls to examine the effects of individual fatty acid groups on colorectal cancer risk as well as their interactions with calcium and fiber intake. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression model according to quartile levels of energy-adjusted fatty acid intake. In the bivariable analyses, the risk of colorectal cancer increased with trans fatty acid (TFA) intake (OR for top vs. bottom quartile =1.46, 95% CI 1.17-1.59, p-value for a trend <0.001), but the associations was substantially attenuated in multivariable analyses (p value for a trend = 0.176). However, a significant linear trend in the multivariable OR (p = 0.029) for TFA was present for subjects with lower calcium intake. Furthermore, multivariable ORs progressively decreased with increasing both omega-3 and omega-6 poly- unsaturated fatty acid intake (p-values for linear trend: 0.033 and 0.011, respectively) for subjects with lower dietary fiber intake. These interactions were also significant or marginally significant (p = 0.085 for TFA, 0.029 for omega-3 and 0.068 for omega-6). Our results suggest that populations with lower intake of luminal modifiers, i.e., calcium and fiber, may have differential risks of colorectal cancer associated with dietary fatty acid intake.

Increased hypolipidemic benefits of cis-9, trans-11 conjugated linoleic acid in combination with trans-11 vaccenic acid in a rodent model of the metabolic syndrome, the JCR:LA-cp rat

BACKGROUND

Conjugated linoleic acid (cis-9, trans-11 CLA) and trans-11 vaccenic acid (VA) are found naturally in ruminant-derived foods. CLA has been shown to have numerous potential health related effects and has been extensively investigated. More recently, we have shown that VA has lipid-lowering properties associated with reduced hepatic lipidogenesis and chylomicron secretion in the JCR:LA-cp rat. The aim of this study was to evaluate potential additional hypolipidemic effects of purified forms of CLA and VA in an animal model of the metabolic syndrome (the JCR:LA-cp rat).

METHODS

Twenty four obese JCR:LA-cp rats were randomized and assigned to one of three nutritionally adequate iso-caloric diets containing 1% w/w cholesterol and 15% w/w fat for 16 wk: 1) control diet (CD), 2) 1.0% w/w cis-9, trans-11 CLA (CLA), 3) 1.0% w/w VA and 1% w/w cis-9, trans-11 CLA (VA+CLA). Lean rats were fed the CD to represent normolipidemic conditions.

RESULTS

Fasting plasma triglyceride (TG), total cholesterol and LDL-cholesterol concentrations were reduced in obese rats fed either the CLA diet or the VA+CLA diet as compared to the obese control group (p < 0.05, p < 0.001; p < 0.001, p < 0.01; p < 0.01, p < 0.001, respectively). The VA+CLA diet reduced plasma TG and LDL-cholesterol to the level of the normolipidemic lean rats and further decreased nonesterified fatty acids compared to the CLA diet alone. Interestingly, rats fed the VA+CLA diet had a higher food intake but lower body weight than the CLA fed group (P < 0.05). Liver weight and TG content were lower in rats fed either CLA (p < 0.05) or VA+CLA diets (p < 0.001) compared to obese control, consistent with a decreased relative protein abundance of hepatic acetyl-CoA carboxylase in both treatment groups (P < 0.01). The activity of citrate synthase was increased in liver and adipose tissue of rats fed, CLA and VA+CLA diets (p < 0.001) compared to obese control, suggesting increased mitochondrial fatty acid oxidative capacity.

CONCLUSION

We demonstrate that the hypolipidemic effects of chronic cis-9, trans-11 CLA supplementation on circulating dyslipidemia and hepatic steatosis are enhanced by the addition of VA in the JCR:LA-cp rat.

Dairy food consumption and obesity-related chronic disease

Dairy food comprises a range of different products with varying nutritional components. In the context of a healthy diet, dairy food may provide protection against and amelioration of chronic diseases related to obesity. These include overweight, insulin resistance/metabolic syndrome/type 2 diabetes, hypertension/stroke, and cardiovascular disease. Eliciting how dairy food may have this impact represents a challenge for modern nutritional science and requires an integration of knowledge from observational studies of population dietary patterns and disease prevalence, and experimental studies testing the effect of dairy food consumption. It also benefits from the recent identification of biomarkers of dairy fat intake and from mechanistic studies that support the plausibility of the observed effects. Future research might discriminate between types of dairy foods and focus on the synergy provided by the food matrix, rather than simply the component parts of the food.

Dissimilar properties of vaccenic versus elaidic acid in beta-oxidation activities and gene regulation in rat liver cells

Vaccenic acid (trans-11-C(18:1)) chemically resembles elaidic acid (trans-9-C(18:1)) which is assumed to increase the risk of cardiovascular diseases, and thus could exert similar effects. Possible different oxidation rates of vaccenic versus elaidic acid were checked in muscles and liver, and through related gene expression in normal rat liver cells. In hepatic mitochondria, carnitine palmitoyltransferase (CPT) I exhibited comparable activity rates with both trans-isomers. CPT II activity was 30% greater (P < 0.05) with vaccenic than with elaidic acid as nonesterified fatty acids (NEFAs) or acyl-CoAs. Activity of the first beta-oxidation step was similar between the isomers in all the tissue slices and liver extracts assayed. Respiration rates were comparable with both trans-isomers as NEFAs in various liver extracts, but were 30% greater (P < 0.05) with vaccenoyl-CoA than with elaidoyl-CoA in liver mitochondria. Vaccenic acid was oxidised 25% more (P < 0.05) by liver peroxisomes than elaidic acid. In hepatocytes cultured with trans- and corresponding cis-C(18:1) isomers, gene expression of CPT I, hydroxyacyl-CoA dehydrogenase and hydroxymethylglutaryl-CoA synthase was at least 100% increased (P < 0.05), but was unchanged with vaccenic acid, relative to controls. In conclusion, the position and geometry of the double bonds in acyl chains are suggested to confer on vaccenic and elaidic acid specific biochemical properties that might differently affect their fates in tissues.

Differential impact of milk fatty acid profiles on cardiovascular risk biomarkers in healthy men and women

BACKGROUND/OBJECTIVES

The objective of this study was to evaluate the impact of three specific ruminant (R) milk fats resulting from modification of the cow's diet on cardiovascular risk factors in healthy volunteers. R-milk fats were characterized by increased content in total trans fatty acids (R-TFAs) and parallel decrease in saturated fatty acids (SFAs).

SUBJECTS/METHODS

A total of 111 healthy, normolipemic men and women have been recruited for a monocentric, randomized, double-blind and parallel intervention, 4-week controlled study. Volunteers consumed three experimental products (butter, dessert cream and cookies) made with one of the three specific milk fats (55 g fat per day). During the first week (run-in period), the subjects consumed on a daily basis dairy products containing 72% SFA/2.85% R-TFA (called 'L0'). For the next 3 weeks of the study (intervention period), the first group continued to consume L0 products. The second group received dairy products containing 63.3% SFA/4.06% R-TFA (called 'L4'), and the third group received dairy products containing 56.6% SFA/12.16% R-TFA (called 'L9').

RESULTS

Plasma concentrations of high-density lipoprotein (HDL)-cholesterol were not significantly altered by either diet (P=0.38). Compared to L0 diet, L4 diet contributed to reduce low-density lipoprotein (LDL)-cholesterol (-0.14+/-0.38 mmol/l, P=0.04), total cholesterol (-0.13+/-0.50 mmol/l, P=0.04), LDL-cholesterol/HDL-cholesterol (-0.14+/-0.36, P=0.03) and total cholesterol/HDL-cholesterol (-0.18+/-0.44, P=0.02).

CONCLUSIONS

Different milk fat profiles can change cardiovascular plasma parameters in human healthy volunteers. A limited increase of the R-TFA/SFA ratio in dairy products is associated with an improvement in some cardiovascular risk factors. However, a further increase in R-TFA/SFA ratio has no additional benefit.

Trans fats in America: a review of their use, consumption, health implications, and regulation

Trans fatty acids have long been used in food manufacturing due in part to their melting point at room temperature between saturated and unsaturated fats. However, increasing epidemiologic and biochemical evidence suggest that excessive trans fats in the diet are a significant risk factor for cardiovascular events. A 2% absolute increase in energy intake from trans fat has been associated with a 23% increase in cardiovascular risk. Although Denmark has shown it is possible to all but eliminate commercial sources of trans fats from the diet, total elimination is not possible in a balanced diet due to their natural presence in dairy and meat products. Thus, the American Heart Association recommends limiting trans fats to <1% energy, and the American Dietetic Association, the Institute of Medicine, US Dietary Guidelines, and the National Cholesterol Education Project all recommend limiting dietary trans-fat intake from industrial sources as much as possible. The presence of small amounts of trans fat in hydrogenated or partially hydrogenated oils/food products will likely cause many Americans to exceed their recommended maximum. This likelihood is exacerbated by the Food and Drug Administration labeling rules, which allow products containing <0.5 g trans fat per serving to claim 0 g trans fat. Many products with almost 0.5 g trans fat, if consumed over the course of a day, may approximate or exceed the 2 g maximum as recommended by American Heart Association, all while claiming to be trans-fat free. Accordingly, greater transparency in labeling and/or active consumer education is needed to reduce the cardiovascular risks associated with trans fats.

Effect of animal and industrial trans fatty acids on HDL and LDL cholesterol levels in humans--a quantitative review

BACKGROUND

Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower HDL cholesterol, raise LDL cholesterol, and increase the risk of coronary heart disease. The effects of conjugated linoleic acid and trans fatty acids from ruminant animals are less clear. We reviewed the literature, estimated the effects trans fatty acids from ruminant sources and of conjugated trans linoleic acid (CLA) on blood lipoproteins, and compared these with industrial trans fatty acids.

METHODOLOGY/PRINCIPAL FINDINGS

We searched Medline and scanned reference lists for intervention trials that reported effects of industrial trans fatty acids, ruminant trans fatty acids or conjugated linoleic acid on LDL and HDL cholesterol in humans. The 39 studies that met our criteria provided results of 29 treatments with industrial trans fatty acids, 6 with ruminant trans fatty acids and 17 with CLA. Control treatments differed between studies; to enable comparison between studies we recalculated for each study what the effect of trans fatty acids on lipoprotein would be if they isocalorically replaced cis mono unsaturated fatty acids. In linear regression analysis the plasma LDL to HDL cholesterol ratio increased by 0.055 (95%CI 0.044-0.066) for each % of dietary energy from industrial trans fatty acids replacing cis monounsaturated fatty acids The increase in the LDL to HDL ratio for each % of energy was 0.038 (95%CI 0.012-0.065) for ruminant trans fatty acids, and 0.043 (95% CI 0.012-0.074) for conjugated linoleic acid (p = 0.99 for difference between CLA and industrial trans fatty acids; p = 0.37 for ruminant versus industrial trans fatty acids).

CONCLUSIONS/SIGNIFICANCE

Published data suggest that all fatty acids with a double bond in the trans configuration raise the ratio of plasma LDL to HDL cholesterol.

Effect of a high intake of conjugated linoleic acid on lipoprotein levels in healthy human subjects

BACKGROUND

Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower high-density lipoprotein (HDL) cholesterol, raise low-density lipoprotein (LDL) cholesterol, and increase the risk of coronary heart disease. The effects of trans fatty acids from ruminants are less clear. We investigated the effect on blood lipids of cis-9, trans-11 conjugated linoleic acid (CLA), a trans fatty acid largely restricted to ruminant fats.

METHODOLOGY/PRINCIPAL FINDINGS

Sixty-one healthy women and men were sequentially fed each of three diets for three weeks, in random order, for a total of nine weeks. Diets were identical except for 7% of energy (approximately 20 g/day), which was provided either by oleic acid, by industrial trans fatty acids, or by a mixture of 80% cis-9, trans-11 and 20% trans-10, cis-12 CLA. After the oleic acid diet, mean (+/- SD) serum LDL cholesterol was 2.68+/-0.62 mmol/L compared to 3.00+/-0.66 mmol/L after industrial trans fatty acids (p<0.001), and 2.92+/-0.70 mmol/L after CLA (p<0.001). Compared to oleic acid, HDL-cholesterol was 0.05+/-0.12 mmol/L lower after industrial trans fatty acids (p = 0.001) and 0.06+/-0.10 mmol/L lower after CLA (p<0.001). The total-to-HDL cholesterol ratio was 11.6% higher after industrial trans fatty acids (p<0.001) and 10.0% higher after CLA (p<0.001) relative to the oleic acid diet.

CONCLUSIONS/SIGNIFICANCE

High intakes of an 80:20 mixture of cis-9, trans-11 and trans-10, cis-12 CLA raise the total to HDL cholesterol ratio in healthy volunteers. The effect of CLA may be somewhat less than that of industrial trans fatty acids.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00529828.

Dietary vaccenic acid has antiatherogenic effects in LDLr-/- mice

Epidemiological evidence has associated dietary trans fatty acids (TFA) with heart disease. TFA are primarily from hydrogenated fats rich in elaidic acid, but dairy products also contain naturally occurring TFA such as vaccenic acid. Our purpose in this study was to compare the effects of consuming a commercially hydrogenated vegetable shortening rich in elaidic TFA (18:1t9) or a butter rich in vaccenic TFA (18:1t11) in the absence and presence of dietary cholesterol on atherosclerosis. LDL receptor deficient (LDLr(-/-)) mice were fed 1 of 8 experimental diets for 14 wk with the fat content replaced by: regular (pork/soy) fat (RG), elaidic shortening (ES), regular butter (RB), vaccenic butter (VB), or an atherogenic diet containing 2% cholesterol with RG (CH+RG), ES (CH+ES), RB (CH+RB), or VB (CH+VB). Serum cholesterol levels were elevated with cholesterol feeding (P < 0.001), whereas serum triglyceride levels were higher only in the CH+RB (P < 0.001) and CH+VB (P < 0.001) groups compared with the other 6 groups. Serum cholesterol and triglyceride levels were significantly lower in the CH+VB group than in the CH+RB group (P < 0.001). Atherosclerosis was stimulated by dietary ES compared with RG (P = 0.021), but CH+ES did not stimulate atherosclerosis beyond CH+RG alone. In contrast, VB did not induce an increase in atherosclerotic plaque formation compared with the RG and RB diets and the CH+VB diet reduced atherosclerosis compared with the other diets containing cholesterol (P < 0.01). In summary, consuming a hydrogenated elaidic acid-rich diet stimulates atherosclerosis, whereas a vaccenic acid-rich butter protects against atherosclerosis in this animal model.

Dietary supplementation with cis-9,trans-11 conjugated linoleic acid and aortic stiffness in overweight and obese adults

BACKGROUND

Animal studies suggest that dietary cis-9,trans-11 (c9,t11) conjugated linoleic acid (CLA) may inhibit or regress the development of atherosclerosis. The effect of CLA on atherosclerosis has not been assessed in humans.

OBJECTIVE

We investigated the effect of c9,t11 CLA supplementation on aortic pulse wave velocity (a marker of atherosclerosis) and on cardiovascular risk factors in overweight and obese but otherwise apparently healthy subjects.

DESIGN

In a double-blind, randomized, placebo-controlled, parallel-group trial, we randomly assigned 401 subjects, aged 40-70 y and with a body mass index (in kg/m(2)) > or = 25, to receive either 4 g CLA/d (2.5 g c9,t11 CLA/d and 0.6 g trans-10,cis-12 CLA/d) or placebo supplements for 6 mo. Aortic pulse wave velocity, blood pressure, anthropometric characteristics, and concentrations of fasting lipid, glucose, insulin, and C-reactive protein were measured before and after supplementation.

RESULTS

During the intervention, mean (+/-SE) pulse wave velocity did not change in the c9,t11 CLA group (Delta0.00 +/- 0.07) compared with the placebo group (Delta0.09 +/- 0.06). There was no effect of c9,t11 CLA supplementation on blood pressure, body composition, insulin resistance, or concentrations of lipid, glucose, and C-reactive protein.

CONCLUSION

This study does not support an antiatherosclerotic effect or an effect on cardiovascular risk factors of c9,t11 CLA. This trial was registered at www.clinicaltrials.gov as NCT00706745.

Estimation of trans fatty acid intake in Japanese adults using 16-day diet records based on a food composition database developed for the Japanese population

BACKGROUND

The Standard Tables of Food Composition in Japan do not include information on trans fatty acids. Previous studies estimating trans fatty acid intake among Japanese have limitations regarding the databases utilized and diet assessment methodologies. We developed a comprehensive database of trans fatty acid food composition, and used this database to estimate intake among a Japanese population.

METHODS

The database was developed using analytic values from the literature and nutrient analysis software encompassing foods in the US, as well as values estimated from recipes or nutrient compositions. We collected 16-day diet records from 225 adults aged 30 to 69 years living in 4 areas of Japan. Trans fatty acid intake was estimated based on the database and the 16-day diet records.

RESULTS

Mean total fat and trans fatty acid intake was 56.9 g/day (27.7% total energy) and 1.7 g/day (0.8% total energy), respectively, for women and 66.8 g/day (25.5% total energy) and 1.7 g/day (0.7% total energy) for men. Trans fatty acid intake accounted for greater than 1% of total energy intake, which is the maximum recommended according to the World Health Organization, in 24.4% of women and 5.7% of men, and was particularly high among women living in urban areas and those aged 30-49 years. The largest contributors to trans fatty acid intake were confectionaries in women and fats and oils in men.

CONCLUSIONS

Although mean trans fatty acid intake was below the maximum recommended intake of the World Health Organization, intake among subgroups was of concern. Further public health efforts to reduce trans fatty acid intake should be encouraged.

Trans-11 vaccenic acid reduces hepatic lipogenesis and chylomicron secretion in JCR:LA-cp rats

Trans-11 vaccenic acid (VA) is the predominant trans isomer in ruminant fat and a major precursor to the endogenous synthesis of cis9,trans11-conjugated linoleic acid in humans and animals. We have previously shown that 3-wk VA supplementation has a triglyceride (TG)-lowering effect in a rat model of dyslipidemia, obesity, and metabolic syndrome (JCR:LA-cp rats). The objective of this study was to assess the chronic effect (16 wk) of VA on lipid homeostasis in both the liver and intestine in obese JCR:LA-cp rats. Plasma TG (P < 0.001), total cholesterol (P < 0.001), LDL cholesterol (P < 0.01), and nonesterified fatty acid concentrations, as well as the serum haptoglobin concentration, were all lower in obese rats fed the VA diet compared with obese controls (P < 0.05). In addition, there was a decrease in the postprandial plasma apolipoprotein (apo)B48 area under the curve (P < 0.05) for VA-treated obese rats compared with obese controls. The hepatic TG concentration and the relative abundance of fatty acid synthase and acetyl-CoA carboxylase proteins were all lower (P < 0.05) in the VA-treated group compared with obese controls. Following acute gastrointestinal infusion of a VA-triolein emulsion in obese rats that had been fed the control diet for 3 wk, the TG concentration was reduced by 40% (P < 0.05) and the number of chylomicron (CM) particles (apoB48) in nascent mesenteric lymph was reduced by 30% (P < 0.01) relative to rats infused with a triolein emulsion alone. In conclusion, chronic VA supplementation significantly improved dyslipidemia in both the food-deprived and postprandial state in JCR:LA-cp rats. The appreciable hypolipidemic benefits of VA may be attributed to a reduction in both intestinal CM and hepatic de novo lipogenesis pathways.

Dairy and industrial sources of trans fat do not impair peripheral insulin sensitivity in overweight women

BACKGROUND

The 2 major dietary sources of trans fatty acids (TFAs) are partially hydrogenated oils and ruminant-derived products. Epidemiologic data suggest that chronic consumption of industrial sources of TFAs could be damaging to insulin sensitivity, but intervention studies on this issue have remained inconclusive.

OBJECTIVE

The trial was designed to compare the effects of dairy compared with industrial sources of TFAs on insulin sensitivity in overweight women.

DESIGN

Sixty-three healthy women with abdominal obesity [waist circumference >88 cm and a body mass index (in kg/m(2)) >28] were recruited. After a run-in period, the volunteers were randomly assigned to consume 1 of 3 four-week diets: 60 g low-TFA lipids/d (0.54 g/d; n = 21), ruminant TFA-rich lipids (4.86 g/d; n = 21), or industrial TFA-rich lipids (5.58 g/d; n = 21). Changes in peripheral insulin sensitivity were assessed by using hyperinsulinemic-euglycemic clamps.

RESULTS

After the intervention period, fasting glycemia and insulinemia and insulin sensitivity were not significantly modified in either group (P > 0.05).

CONCLUSIONS

These data indicate that consumption of dairy- and industrial-source TFAs for 4 wk at nutritional levels do not impair peripheral insulin sensitivity in insulin-resistant women. Our study may not preassess the effects of TFAs in normal insulin-sensitive individuals. This trial was registered at ClinicalTrials.gov as NCT00617435.

Winter/spring changes in fatty acid composition of farmhouse Idiazabal cheese due to different flock management systems

Typically, two different flock managements are employed by basque sheepherders in winter and spring. Thus, seasonal changes in the fatty acid (FA) composition of Idiazabal PDO farmhouse cheeses were studied. Ewe's raw milk cheeses elaborated in winter and spring were collected after 120 days of ripening from 10 Idiazabal PDO farmhouses. In winter, concentrate and conserved forages were fed, whereas a part-time grazing system was adopted from spring onward. Spring cheeses had less (P <or= 0.05) saturated FA and higher (P <or= 0.05) content of unsaturated FA, including trans-FA (mainly trans-vaccenic acid) and conjugated linoleic acid (CLA), branched-chain FA (BCFA), and n-3 FA. Principal component analysis (PCA) separated winter and spring cheeses into two groups by the combination of two principal components (84.2% of variance). Fresh pasture in the diet enhanced desirable FA and lowered atherogenicity index in cheeses, supporting the benefits of using a part-time grazing system for the consumer.

Trans fatty acids: effects on metabolic syndrome, heart disease and diabetes

The major dietary sources of trans fatty acids (TFAs) in most countries are partially hydrogenated vegetable oils. TFA consumption is a modifiable dietary risk factor for metabolic syndrome, diabetes mellitus, and coronary heart disease. Here, we review the available data on various effects of TFAs, including metabolic and signaling pathways that mediate these effects, affected tissues, and relationships with clinical end points. TFA consumption causes metabolic dysfunction: it adversely affects circulating lipid levels, triggers systemic inflammation, induces endothelial dysfunction, and, according to some studies, increases visceral adiposity, body weight, and insulin resistance. Dietary TFAs influence the function of multiple cell types, including hepatocytes, adipocytes, macrophages and endothelial cells. Among dietary fats and nutrients, TFAs seem to have a unique cardiometabolic imprint that is linked to insulin-resistance and metabolic-syndrome pathways. Consistent with these adverse physiological effects, consumption of even small amounts of TFAs (2% of total energy intake) is consistently associated with a markedly increased incidence of coronary heart disease. Relationships between TFA consumption and diabetes mellitus have been less consistent, possibly owing to differences in study designs. Nevertheless, the documented adverse effects of TFAs underscore their potential to cause harm and the importance of policy measures to minimize consumption of industrially produced TFAs.

Association between trans-fatty acids in erythrocytes and pro-atherogenic lipid profiles among Canadian Inuit of Nunavik: possible influences of sex and age

Dietary exposure to trans-fatty acids (TFA) is likely to be high among Canadian Inuit; yet no data are available on the physiological effects of TFA in this population. The purpose of the present study was to assess the association between TFA and plasma lipid profiles in Inuit men and women living in Nunavik (Québec, Canada). In a cross-sectional, population-based survey, a total of 795 Nunavik Inuit eligible participants gave a blood sample. Exposure to TFA was assessed by their relative proportion in erythrocyte membrane. We performed multiple regression analysis using plasma lipids or their linear combinations as the dependent variables and TFA as the main predictor, adjusting for potential confounders. The associations varied markedly between the sexes and according to age. In men (n 357, aged 36.3 (sd 14.3) years, TFA 1.24 (sd 0.54) %), TFA tended to be negatively associated with HDL-cholesterol (HDL-C), apoA1 and LDL particle size, and positively associated with non-HDL-C, LDL-cholesterol (LDL-C), apoB100, the apoB100:apoA1 ratio and the ratios of total cholesterol (TC), LDL-C and TAG to HDL-C. No such trends were observed in women (n 438, aged 37.0 (sd 14.1) years, TFA 1.16 (sd 0.54) %), except for HDL-C and apoA1 in women aged 50 years and more. These results suggest that TFA could raise the risk of CHD in Inuit men at least through their physiological effects on plasma lipids. The differential associations reported in pre- and postmenopausal women need to be reproduced in other populations and in experimental studies addressing the influence of sex hormones in response to dietary fats.

A reappraisal of the impact of dairy foods and milk fat on cardiovascular disease risk

Background

This review provides a reappraisal of the potential effects of dairy foods, including dairy fats, on cardiovascular disease (CVD)/coronary heart disease (CHD) risk. Commodities and foods containing saturated fats are of particular focus as current public dietary recommendations are directed toward reducing the intake of saturated fats as a means to improve the overall health of the population. A conference of scientists from different perspectives of dietary fat and health was convened in order to consider the scientific basis for these recommendations.

Aims

This review and summary of the conference focus on four key areas related to the biology of dairy foods and fats and their potential impact on human health: (a) the effect of dairy foods on CVD in prospective cohort studies; (b) the impact of dairy fat on plasma lipid risk factors for CVD; (c) the effects of dairy fat on non-lipid risk factors for CVD; and (d) the role of dairy products as essential contributors of micronutrients in reference food patterns for the elderly.

Conclusions

Despite the contribution of dairy products to the saturated fatty acid composition of the diet, and given the diversity of dairy foods of widely differing composition, there is no clear evidence that dairy food consumption is consistently associated with a higher risk of CVD. Thus, recommendations to reduce dairy food consumption irrespective of the nature of the dairy product should be made with caution.

Lifestyle approaches and dietary strategies to lower LDL-cholesterol and triglycerides and raise HDL-cholesterol

This article discusses specific dietary factors as well as dietary patterns that affect the major coronary heart disease (CHD) lipid risk factors (ie, LDL-C, HDL-C, and TG). Based on a very large evidence base, it is clear that diet and lifestyle practices can markedly affect these major CHD lipid risk factors, and consequently decrease CHD risk substantively.

Vaccenic acid favourably alters immune function in obese JCR:LA-cp rats

Vaccenic acid (VA) is a ruminant-derived trans-fat and precursor of conjugated linoleic acid (CLA). The objective of the present study was to explore the effects of VA on immune function in a model of the metabolic syndrome, JCR:LA-cp rats. Lean (2:1 mix of +/cp and +/+) and obese (cp/cp) rats, aged 8 weeks, were fed a control (0% VA) or a VA diet (1.5% (w/w) VA) for 3 weeks (twenty rats per group). Splenocytes and mesenteric lymph node (MLN) immune cell phenotypes (flow cytometry), ex vivo cytokine production (ELISA) and phospholipid fatty acid concentrations were measured. Obese rats had higher proportions of splenic macrophages, total T-cells, helper T-cells (total and percentage CD25+), cytotoxic T-cells (total and percentage CD25+) and produced higher concentrations of IL-6 to concanavalin A (ConA) compared with lean rats. Obese rats had lower proportions of MLN T-cells, new T-cells (CD3+CD90+) and cytotoxic T-cells, but higher proportions of helper cells that were CD45RC+, CD25+ and CD4lo, and produced higher concentrations of IL-2, IL-10, interferon gamma and TNFalpha in response to ConA compared with lean rats. VA was higher in plasma phospholipids and both VA and CLA (cis-9, trans-11) were higher in MLN phospholipids compared with control-fed rats. Lean VA-fed rats had lower proportions of MLN and splenocyte CD45RC+ helper cells, and helper T-cells. Splenocytes from VA-fed rats produced 16-23% less IL-2, IL-10 and TNFalpha compared with controls. VA normalised production of MLN IL-2 and TNFalpha in obese rats to levels similar to those seen in lean rats. These results indicate that dietary VA favourably alters the pro-inflammatory tendency of mesenteric lymphocytes from JCR:LA-cp rats.

trans-C18:1 isomers in cheeses enriched in unsaturated fatty acids and manufactured with different milk fat globule sizes

Increasing the knowledge on dietary fat composition, mainly the minor components, will improve the nutritional value of foods and their labeling. In this study, we examined the trans-octadecenoic acid (C18:1) composition of Emmental cheeses enriched in unsaturated fatty acids (FA) and manufactured with milks produced by cows selected to produce small and large fat globules. The FA composition of the milks was not significantly ( P > 0.05) different from the FA composition of the corresponding Emmental cheeses. Increasing the unsaturated FA content of the cheeses using dietary manipulations lead to an increase in the trans-C18:1 and changed their isomeric profiles. In milk fat produced with the linseed-enriched diet, the trans-10 C18:1 concentration was greater than trans-11 C18:1 (vaccenic acid), which is classically the major trans-C18:1 in milk fat. The content in trans-C18:1 and more particularly in trans-10 C18:1 was negatively correlated with the size of fat globules ( r (2) = 0. 82 and 0.87, respectively) and related to milk fat depression. The trans-C18:1 content was negatively correlated with the saturated FA (slope = -0.35; r (2) = 0.81) and positively correlated with the unsaturated (slope = 0.29; r (2) = 0.85) and monounsaturated (slope = 0.32; r (2) = 0.81) FA. Focusing on the health-related considerations of fat in food products, further nutritional studies are needed to elucidate the role of trans-C18:1 isomers.