Coagulation and Fibrinolysis Factors in Healthy Subjects Consuming High Stearic or Trans Fatty Acid Diets

Trans fatty acids and cholesterol levels: An evidence map of the available science

High intakes of industrial trans fatty acids (iTFA) increase circulating low density lipoprotein cholesterol (LDL-C) levels, which has implicated iTFA in coronary heart disease (CHD) risk. Published data on iTFA and LDL-C, however, represent higher intake levels than the U.S. population currently consume. This study used state-of-the-art evidence mapping approaches to characterize the full body of literature on LDL-C and iTFA at low intake levels. A total of 32 independent clinical trials that included at least one intervention or control group with iTFA at ≤3%en were found. Findings indicated that a wide range of oils and interventions were used, limiting the ability to determine an isolated effect of iTFA intake. Few data points were found for iTFA at <3%en, with the majority of low-level exposures actually representing control group interventions containing non-partially hydrogenated (PHO) oils. Further, it appears that few dose-response data points are available to assess the relationship of low levels of iTFA, particularly from PHO exposure, and LDL-C. Therefore, limited evidence is available to determine the effect of iTFA at current consumption levels on CHD risk.

Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: a systematic review

BACKGROUND

High stearic acid (STA) soybean oil is a trans-free, oxidatively stable, non-LDL-cholesterol-raising oil that can be used to replace trans fatty acids (TFAs) in solid fat applications.

OBJECTIVE

The objective was to assess the cardiovascular health effects of dietary STA compared with those of trans, other saturated, and unsaturated fatty acids.

DESIGN

We reviewed epidemiologic and clinical studies that evaluated the relation between STA and cardiovascular disease (CVD) risk factors, including plasma lipids and lipoproteins, hemostatic variables, and inflammatory markers.

RESULTS

In comparison with other saturated fatty acids, STA lowered LDL cholesterol, was neutral with respect to HDL cholesterol, and directionally lowered the ratio of total to HDL cholesterol. STA tended to raise LDL cholesterol, lower HDL cholesterol, and increase the ratio of total to HDL cholesterol in comparison with unsaturated fatty acids. In 2 of 4 studies, high-STA diets increased lipoprotein(a) in comparison with diets high in saturated fatty acids. Three studies showed increased plasma fibrinogen when dietary STA exceeded 9% of energy (the current 90th percentile of intake is 3.5%). Replacing industrial TFAs with STA might increase STA intake from 3.0% (current) to approximately 4% of energy and from 4% to 5% of energy at the 90th percentile. One-to-one substitution of STA for TFAs showed a decrease or no effect on LDL cholesterol, an increase or no effect on HDL cholesterol, and a decrease in the ratio of total to HDL cholesterol.

CONCLUSIONS

TFA intake should be reduced as much as possible because of its adverse effects on lipids and lipoproteins. The replacement of TFA with STA compared with other saturated fatty acids in foods that require solid fats beneficially affects LDL cholesterol, the primary target for CVD risk reduction; unsaturated fats are preferred for liquid fat applications. Research is needed to evaluate the effects of STA on emerging CVD risk markers such as fibrinogen and to understand the responses in different populations.

An oil mixture with trans-10, cis-12 conjugated linoleic acid increases markers of inflammation and in vivo lipid peroxidation compared with cis-9, trans-11 conjugated linoleic acid in postmenopausal women

A mixture of trans-10, cis-12 (t10,c12) and cis-9, trans-11 (c9,t11) conjugated linoleic acid (CLA mixture) reduced atherosclerosis in animals, thus the effect of these isomers on endothelial dysfunctions leading to inflammation and atherosclerosis is of interest. We gave 75 healthy postmenopausal women a daily supplement of 5.5 g of oil rich in either CLA mixture, an oil rich in the naturally occurring c9,t11 CLA (CLA milk), respectively, or olive oil for 16 wk in a double-blind, randomized, parallel intervention study. We sampled blood and urine before and after the intervention. The ratios of total cholesterol:HDL cholesterol and concentrations of C-reactive protein, fibrinogen, and plasminogen activator inhibitor-1 were significantly higher in women supplemented with the CLA mixture than in those supplemented with CLA milk. Plasma triacylglycerol was significantly higher and HDL cholesterol was lower in women supplemented with the CLA mixture than with olive oil. Both CLA supplements increased lipid peroxidation, a marker of in vivo oxidative stress measured as urinary free 8-iso-prostaglandin F(2alpha). However, the CLA mixture increased lipid peroxidation more than the CLA milk did. The plasma cytokines interleukin-6 and tumor necrosis factor-alpha were not affected by the treatments, nor were any of the other variables measured. In conclusion, oil containing trans-10,cis-12 CLA has several adverse effects on classical and novel markers of coronary vascular disease, whereas the c9,t11 CLA isomer is more neutral, except for a small but significant increase in lipid peroxidation compared with olive oil.

Effect of modified dairy fat on fasting and postprandial haemostatic variables in healthy young men

It has been suggested that milk fat, due to its content of saturated fatty acids, may have a thrombogenic effect. In the present study the fatty acid profile of milk fat was modified by changing the feeding regimens of cows and the effect on haemostatic variables of a diet containing the modified milk fat (M) was compared with that of a diet containing milk fat of typical Danish composition (D). In the modified fat 16% of the saturated fatty acid (C12–C16) content was replaced mainly by oleic acid. Eighteen subjects were fed on two strictly controlled isoenergetic diets containing 40% energy from total fat (30% energy from the test fats) for periods of 4 weeks in a study with a crossover design. Fasting samples were taken in the last week of each study period. Postprandial samples were taken on day 21, 3 h after lunch (n18), and on the last day of the study 2, 4, 6 and 8 h after a fat load containing 1·2 g of one of the milk fats/kg body weight (n8). After 4 weeks' dietary intervention fasting plasma factor VII coagulant (FVIIc) activity, tissue-type plasminogen activator (t-PA) activity, plasminogen activator inhibitor (PAI-1) antigen and β-thromboglobulin did not differ between diets M and D. Postprandially FVIIc and t-PA activities increased (P< 0·001) and PAI-1 antigen and PAI-1 activity decreased (P< 0·001) as compared with fasting values, regardless of diet. After the fat load, the postprandial increase in FVIIc was marginally lower after diet M than diet D (diet effect,P< 0·05). In conclusion, the modified milk fat obtained by the applied feeding strategy had virtually the same effects on haemostatic variables as conventional milk fat.

Dietary trans fatty acids: Review of recent human studies and food industry responses

Dietary trans FA at sufficiently high levels have been found to increase low density lipoprotein (LDL)-cholesterol and decrease high density lipoprotein (HDL)-cholesterol (and thus to increase the ratio of LDL-cholesterol/HDL-cholesterol) compared with diets high in cis monounsaturated FA or PUFA. The dietary levels of trans FA at which these effects are easily measured are around 4% of energy or higher to increase LDL-cholesterol and around 5 to 6% of energy or higher to decrease HDL-cholesterol, compared with essentially trans-free control diets. Very limited data at lower levels of intake (less than 4% of energy) are available. Most health professional organizations and some governments now recommend reduced consumption of foods containing trans FA, and effective January 1, 2006, the U.S. Food and Drug Administration requires the labeling of the amounts of trans FA per serving in packaged foods. In response, the food industry is working on ways to eliminate or greatly reduce trans FA in food products. Current efforts focus on four technological options: (i) modification of the hydrogenation process, (ii) use of interesterification, (iii) use of fractions high in solids from natural oils, and (iv) use of trait-enhanced oils. Challenges to the food industry in replacing trans FA in foods are to develop formulation options that provide equivalent functionality, are economically feasible, and do not greatly increase saturated FA content.

Effects of butter high in ruminant trans and monounsaturated fatty acids on lipoproteins, incorporation of fatty acids into lipid classes, plasma C-reactive protein, oxidative stress, hemostatic variables, and insulin in healthy young men

BACKGROUND

Evidence suggests that ruminant trans fatty acids (FAs), such as vaccenic acid, do not increase the risk of ischemic heart disease (IHD). However, the effects of ruminant trans FAs on risk markers of IHD have been poorly investigated.

OBJECTIVE

The objective was to investigate the effect of butter with a naturally high content of vaccenic acid and a concomitantly higher content of monounsaturated FAs on classic and novel risk markers of IHD.

DESIGN

In a double-blind, randomized, 5-wk, parallel intervention study, 42 healthy young men were given 115 g fat/d from test butter that was high in vaccenic acid (3.6 g vaccenic acid/d) or a control butter with a low content of vaccenic acid. Blood and urine samples were collected before and after the intervention.

RESULTS

The intake of the vaccenic acid-rich diet resulted in 6% and 9% lower total cholesterol and plasma HDL-cholesterol concentrations, respectively, than did the intake of the control diet (P = 0.05 and 0.002, respectively), whereas the ratio of total to HDL cholesterol did not differ significantly between the groups. The FA composition of lipid classes reflected the FAs' proportion of the test butter. No other differences were observed.

CONCLUSIONS

Butter high in ruminant trans and monounsaturated FAs resulted in significantly lower total and HDL cholesterol than did the control butter with higher amounts of saturated FAs. It may be that the differences were due to the greater content of monounsaturated FAs and the lesser content of saturated FAs in the butter rich in ruminant trans FAs, rather than to the content of vaccenic acid per se.

Chocolate and prevention of cardiovascular disease: a systematic review

Background

Consumption of chocolate has been often hypothesized to reduce the risk of cardiovascular disease (CVD) due to chocolate's high levels of stearic acid and antioxidant flavonoids. However, debate still lingers regarding the true long term beneficial cardiovascular effects of chocolate overall.

Methods

We reviewed English-language MEDLINE publications from 1966 through January 2005 for experimental, observational, and clinical studies of relations between cocoa, cacao, chocolate, stearic acid, flavonoids (including flavonols, flavanols, catechins, epicatechins, and procynadins) and the risk of cardiovascular disease (coronary heart disease (CHD), stroke). A total of 136 publications were selected based on relevance, and quality of design and methods. An updated meta-analysis of flavonoid intake and CHD mortality was also conducted.

Results

The body of short-term randomized feeding trials suggests cocoa and chocolate may exert beneficial effects on cardiovascular risk via effects on lowering blood pressure, anti-inflammation, anti-platelet function, higher HDL, decreased LDL oxidation. Additionally, a large body of trials of stearic acid suggests it is indeed cholesterol-neutral. However, epidemiologic studies of serum and dietary stearic acid are inconclusive due to many methodologic limitations. Meanwhile, the large body of prospective studies of flavonoids suggests the flavonoid content of chocolate may reduce risk of cardiovascular mortality. Our updated meta-analysis indicates that intake of flavonoids may lower risk of CHD mortality, RR = 0.81 (95% CI: 0.71–0.92) comparing highest and lowest tertiles.

Conclusion

Multiple lines of evidence from laboratory experiments and randomized trials suggest stearic acid may be neutral, while flavonoids are likely protective against CHD mortality. The highest priority now is to conduct larger randomized trials to definitively investigate the impact of chocolate consumption on long-term cardiovascular outcomes.

Influence of stearic acid on hemostatic risk factors in humans

Stearic acid has been claimed to be prothrombotic. Elevated plasma factor VII coagulant activity (FVIIc) may raise the risk of coronary thrombosis in the event of plaque rupture. Fibrinogen, an acute-phase protein, is necessary for normal blood clotting; however, elevated levels of fibrinogen increase the risk of coronary heart disease (CHD). Here I report the results of three controlled, human dietary intervention studies, which used a randomized crossover design to investigate the hemostatic effects of stearic acid-rich test diets in healthy young men. A diet high in stearic acid (shea butter) resulted in a 13% lower fasting plasma FVIIc than a high palmitic acid diet, and was 18% lower than a diet high in myristic and lauric acids (P = 0.001) after 3 wk of intervention. The stearic acid-rich test fat increased plasma fibrinogen concentrations slightly compared with the myristic-lauric acid diet (P < 0.01). When investigating the acute effects of fatty meals, those high in stearic acid (synthesized test fat) resulted in a smaller postprandial increase in FVII than those high in trans and oleic FA, indicating a smaller increase in activated FVII after ingesting stearic acid compared with fats high in monounsaturated FA, probably caused by lower postprandial lipemia. Thus, the present investigations did not find dietary stearic acid to be more thrombogenic, in either fasting effects compared with other long-chain FA, or in acute effects compared with dietary unsaturated FA, including trans monounsaturated FA. The slightly increased effect on fasting plasma fibrinogen may be biologically insignificant, but it should be investigated further.

Fatty acids and atherosclerotic risk

Most research concerning the effects of dietary fatty acids on atherosclerotic risk has focused on their effects on lipid and lipoprotein metabolism. However, it is known that fatty acids also influence a number of other relevant mechanisms involved in atherosclerosis such as lipid peroxidation, inflammation and haemostasis. The most favourable distribution of cholesterol over the various lipoproteins is achieved when saturated and trans fatty acids are replaced by a mixture of cis-unsaturated fatty acids. Furthermore, fatty acids from fish oil lower triacylglycerol concentrations. Effects on other atherosclerotic risk markers are less evident. Monounsaturated fatty acids maybe preferable above other fatty acids with respect to low-density lipoprotein oxidation as measured by indirect in vitro assays. The relevance of these assays for the in vivo situation is, however, limited. With respect to inflammation, mainly the effects of n-3 polyunsaturated fatty acids from fish oil have been studied, but results were inconsistent. Also results from studies evaluating the effects of fatty acids on haemostatic risk markers were inconsistent, which may be partly related to the use of different analytical methods. The most consistent finding however is the potential beneficial effect of moderate intakes of fish oil on platelet aggregation. Furthermore, reducing total fat intake rather than changing the fatty acid composition of the diet may beneficially affect the coagulation system. In conclusion, while beneficial effects on atherosclerotic risk are mainly ascribed to cis-unsaturated fatty acids, it remains debateable whether trans and saturated fatty acids in the diet have to be replaced by cis-unsaturated fatty acids or by carbohydrates. To answer this question adequately more validated methods are needed that reflect in vivo lipid peroxidation, inflammation and haemostasis.

A Diet Rich in Coconut Oil Reduces Diurnal Postprandial Variations in Circulating Tissue Plasminogen Activator Antigen and Fasting Lipoprotein (a) Compared with a Diet Rich in Unsaturated Fat in Women

The effects of high and low fat diets with identical polyunsaturated/saturated fatty acid (P/S) ratios on plasma postprandial levels of some hemostatic variables and on fasting lipoprotein (a) [Lp(a)] are not known. This controlled crossover study compared the effects of a high fat diet [38.4% of energy (E%) from fat; HSAFA-diet, P/S ratio 0.14], a low fat diet (19.7 E% from fat; LSAFA-diet, P/S ratio 0.17), both based on coconut oil, and a diet with a high content of monounsaturated fatty acids (MUFA) and PUFA (38.2 E% from fat; HUFA-diet, P/S ratio 1.9) on diurnal postprandial levels of some hemostatic variables (n = 11) and fasting levels of Lp(a) (n = 25). The postprandial plasma concentration of tissue plasminogen activator antigen (t-PA antigen) was decreased when the women consumed the HSAFA-diet compared with the HUFA-diet (P = 0.02). Plasma t-PA antigen was correlated with plasminogen activator inhibitor type 1 (PAI-1) activity when the participants consumed all three diets (Rs = 0.78, P < 0.01; Rs = 0.76, P < 0.01; Rs = 0.66, P = 0.03; on the HSAFA-, the LSAFA- and the HUFA-diet, respectively), although the diets did not affect the PAI-1 levels. There were no significant differences in postprandial variations in t-PA activity, factor VII coagulant activity or fibrinogen levels due to the diets. Serum fasting Lp(a) levels were lower when women consumed the HSAFA-diet (13%, P < 0.001) and tended to be lower when they consumed the LSAFA-diet (5.3%, P = 0.052) than when they consumed the HUFA-diet. Serum Lp(a) concentrations did not differ when the women consumed the HSAFA- and LSAFA-diets. In conclusion, our results indicate that a coconut oil-based diet (HSAFA-diet) lowers postprandial t-PA antigen concentration, and this may favorably affect the fibrinolytic system and the Lp(a) concentration compared with the HUFA-diet. The proportions of dietary saturated fatty acids more than the percentage of saturated fat energy seem to have a beneficial influence on Lp(a) levels.

High intakes of trans monounsaturated fatty acids taken for 2 weeks do not influence procoagulant and fibrinolytic risk markers for CHD in young healthy men

Dietary trans fatty acids are associated with increased risk of CHD. We hypothesized that the changes in plasma lipids associated with a high intake of trans fatty acids would cause adverse effects on procoagulant and fibrinolytic activities. A randomized crossover controlled feeding study was conducted in twenty-nine men. A trans-rich diet supplying 10 % energy as trans- 18:1 was compared with diets in which the trans fatty acids were replaced either with carbohydrate or oleate; each diet was taken for 2 weeks in random order. Fasting fibrinogen and d-dimer concentrations and factor VII coagulant, plasminogen activator inhibitor type 1 and tissue plasminogen activator did not differ between diets. Postprandially, tissue plasminogen activator activity increased and plasminogen activator inhibitor type 1 activity decreased on all diets. Factor VIIc increased postprandially by 15 and 17 % on the trans and oleate diets respectively, compared with an 11 % increase on the carbohydrate diet; the mean difference between oleate and carbohydrate diets was 6 (95 % CI 0.2, 11.9) %. The LDL-cholesterol:HDL-cholesterol and apolipoprotein B : apolipoprotein A-I ratios increased by 13 (95 % CI 5.7, 21.8) and 10 (95 % CI 3.1, 17.2) % respectively on the trans diet compared with the oleate diet and by 6 (95 % CI 0.1,12.7) and 7 (95 % CI 0, 13.5) % respectively compared with the carbohydrate diet. Plasma HDL2-cholesterol concentration was 18 (95 % CI 0.7, 35.9) % lower on the trans diet compared with the oleate diet. The results confirm adverse effects of trans fatty acids on HDL-cholesterol concentrations, but suggest that trans fatty acids do not have any specific effects on known haemostatic risk markers for cardiovascular disease in healthy young men in the short-term.

Metabolic effects of trans fatty acids on an experimental dietary model

The aim of the present study was to investigate the potential nutritional and metabolic impact of trans (t) fatty acids (FA) on an appropriate experimental dietary model. Since previously reported experimental designs have been matter of concern, we developed a dietary model to compare the effect of t isomers and/or the saturation of FA independently of other variables. Wistar rats were fed diets containing identical amounts of nutrients and high levels of dietary fats (200 g/kg) for 30 d. Dietary fat rich in t-FA was compared with fat rich in saturated (s) FA or rich in cis (c) FA, maintaining the same length of C chain of the FA. The fats were obtained through isomerization or hydrogenation of the c-FA present in the control fat. Apparent fat absorption, energy efficiency and triacylglycerol levels in serum and liver were different in rats fed t-FA or s-FA than c-FA. The apparent fat absorption was (%): s-FA 85.7 (sd 3.4)<t-FA 93.1 (sd 0.4)<c-FA 96.7 (sd 1.1) (P<0.05). The efficiency of energy utilization was lower in t-FA (11.7 %) and s-FA (18.5 %) diets, reaching statistical significance only between s-FA and c-FA. A striking finding was the change in the lipid profile in serum and liver. Serum and hepatic triacylglycerol levels were greater for t-FA and s-FA diets than in c-FA; however, the increases on serum triacylglycerol concentrations were greater with the s-FA diet and the increases on hepatic triacylglycerol content were greater with t-FA. Knowledge of the t-FA effects on this kind of experimental dietary model could contribute to determine the potential risk of t-FA intake for man.

The impact of angiotensin II receptor blockade and the DASH diet on markers of endogenous fibrinolysis

Hypertension is associated with impaired fibrinolysis. Both angiotensin receptor blockers (ARB) and the DASH (Dietary Approaches to Stop Hypertension) diet effectively lower blood pressure in hypertensive patients. Some evidence suggests that treatment with ARBs could increase fibrinolysis, however, data is conflicting. The impact of the DASH diet on fibrinolytic parameters is not known. Fifty-five hypertensive participants (35 African-American, 20 white) were randomly assigned to receive 8 weeks of either a control diet or the DASH diet. The diets did not differ in sodium content (approximately 3 g/day). Within each diet, individuals were randomly assigned to receive losartan or placebo for 4 weeks in double-blind, cross-over fashion. Tissue plasminogen activator (t-PA) antigen, t-PA activity, plasminogen activator inhibitor-1 (PAI-1) activity and plasma renin activity (PRA) were measured at the end of a 2-week run-in period on the control diet and after each treatment period. The DASH diet did not affect markers of fibrinolysis. Losartan significantly lowered t-PA antigen levels (-1.8 ng/mL, P = 0.045), but had no effect on t-PA or PAI-1 activities. This effect was more pronounced in whites (-4.1 ng/mL (P = 0.003)) compared with African-Americans (-0.3 ng/mL (P = 0.7), P-interaction = 0.03). Results were not materially affected by adjustment for basline values or changes in blood pressure. This study demonstrates that losartan reduces t-PA antigen levels in white, but not African-American hypertensive individuals. In contrast, the DASH diet had no significant effect on markers of fibrinolysis in whites or African-Americans.

Influence of a stearic acid-rich structured triacylglycerol on postprandial lipemia, factor VII concentrations, and fibrinolytic activity in healthy subjects

BACKGROUND

An elevated postprandial lipid concentration is believed to be atherogenic and to increase the risk of thrombosis.

OBJECTIVE

The objective was to test whether the consumption of a stearic acid-rich structured triacylglycerol has adverse effects on postprandial fibrinolytic activity and lipemia, factor VII coagulant (FVII:c) activity, and activated FVII (FVIIa) concentrations.

DESIGN

A randomized crossover design was used to compare the effects on middle-aged healthy men (n = 17) and women (n = 18) of meals enriched with cocoa butter, high-oleate sunflower oil (oleate), or a structured triacylglycerol containing stearic acid.

RESULTS

The mean increases from fasting in plasma triacylglycerol 3 h after the oleate, cocoa butter, and structured triacylglycerol meals were 1.36 (95% CI: 1.17, 1.56), 1.39 (1.17,1.63), and 0.65 (0.50, 0.82) mmol/L, respectively. Tissue plasminogen activator activity increased and plasminogen activator type 1 activity decreased after all 3 meals. Plasma FVII:c increased after the oleate and cocoa butter meals but not after the structured triacylglycerol meal. The values 6 h after the oleate and cocoa butter meals were 11.3% (7.0%, 15.6%) and 9.9% (4.7%, 15.2%), respectively, and were significantly different (P < 0.0001 and P = 0.001, respectively) from the value after the triacylglycerol meal [2.1% (-1.1%, 5.3%)]. Plasma FVIIa increased after all 3 meals, more so after the oleate and cocoa butter meals than after the structured triacylglycerol meal.

CONCLUSION

The consumption of stearic acid in the form of a structured triacylglycerol leads to less of an increase in plasma triacylglycerol and in FVII:c than does a meal enriched in cocoa butter or oleate.

Partially hydrogenated soybean oil reduces postprandial t-PA activity compared with palm oil

The effects of dietary trans fatty acids on fasting and diurnal variation in hemostatic variables are not known. This study compares the effects of three diets with three different margarines, one based on palm oil (PALM-diet), one based on partially hydrogenated soybean oil (PHSO, TRANS-diet) and one with a high content of polyunsaturated fatty acids (PUFA-diet) on diurnal postprandial hemostatic variables. A strictly controlled dietary Latin square study was performed and nine young female participants consumed each of the diets for 17 days in a random order. The sum of the cholesterol-increasing fatty acids (C12:0, C14:0, C16:0) was 36.3% of total fatty acids in the PALM-diet, the same as the sum of saturated-(C12:0, C14:0, C16:0) (12.5%) and trans fatty acids (23.1%) in the TRANS-diet. The sum of C12:0, C14:0 and C16:0 was 20.7% in the PUFA-diet. The amount of fat made up 30-31% of energy in all diets. Nine participants completed the study. The diurnal postprandial state level of tissue plasminogen activator (t-PA) activity was significantly decreased on the TRANS-diet compared with the PALM-diet. t-PA activity was also decreased on the PUFA-diet compared with PALM-diet but the difference was below statistical significance (P=0.07, Bonferonni adjusted). There were no significant differences in either fasting levels or in circadian variation of t-PA antigen, PAI-1 activity, PAI-antigen, factor VII coagulant activity or fibrinogen between the three diets. Our results indicate that dietary trans fatty acids from PHSO has an unfavourable effect on postprandial t-PA activity and thus possibly on the fibrinolytic system compared with palm oil.

Dietary trans fatty acid

Trans fatty acids are unsaturated fatty acids that contain at least one double bond in the trans configuration. In the diet they occur at relatively low levels in meat and dairy products as a by-product of fermentation in ruminant animals or in hydrogenated fats as a consequence of the hydrogenation process. In general, dietary hydrogenated fat/trans fatty acids have been reported to increase LDL cholesterol levels relative to oil in the natural state or cis fatty acids. In contrast, dietary hydrogenated fat/trans fatty acids have been reported have to have little effect or decrease HDL cholesterol levels, the later observation restricted to relatively high intakes of trans fatty acids. These two effects result in higher, therefore less favorable, total or LDL cholesterol/HDL cholesterol ratios. Significant increases in Lp(a) levels have been reported after consumption of diets relatively high in trans fatty acids compared with either unsaturated or saturated fatty acids. However, the magnitude of the change is for the most part small and the physiological significance of this observation has yet to be resolved. Data related to the mechanism by which hydrogenated fat/trans fatty acids alter serum lipid levels and other risk factors for cardiovascular disease are in the nascent stages. At this time it would appear prudent that public health recommendations should be aimed at encouraging the moderate consumption of products low in saturated fat or minimally hydrogenated. Trans fatty acids intake should not be stressed at the expense of saturated fat but should augment it.

Dietary treatment of thrombogenic disorders related to the metabolic syndrome

The increased risk of coronary heart disease associated with the metabolic syndrome may be partially explained by prothrombotic deviations of the haemostatic system. Individuals with insulin resistance, dyslipidaemia and obesity are characterized by elevated plasma fibrinogen and factor VII coagulant activity levels and raised concentrations of plasminogen-activator inhibitor, the main inhibitor of endogenous fibrinolysis. These haemostatic abnormalities may be corrected with dietary treatment of the underlying clinical disorder. Dietary trials of diseased and healthy volunteers suggest that the optimal antithrombotic diet is a low-fat diet with a high content of foods rich in complex carbohydrates and dietary fibre. The dietary fatty acid composition has a profound effect on blood lipids, but seems of minor importance for the haemostatic system.

Trans fatty acids and cardiovascular disease risk

Recent studies continue to confirm previous observations that trans fatty acids elevate low density lipoprotein cholesterol levels, and at relatively high intakes decrease high density lipoprotein cholesterol levels. Considerable interest is focused on the potential benefits of trans-free margarines. Both adipose and plasma trans fatty acid levels reflect dietary intake. Current estimates of trans fatty acid intake in developed countries range from 0.5 to 2.6% of energy, contributed to primarily by differences in food availability and preference, and partly by the methodological differences used to calculate the data.

Diet and hemostatic factors

The coagulation, fibrinolytic, and platelet activating systems are complex and interact extensively, and with other systems such as inflammation. Key reactions often require biomembranes, suggesting that dietary lipids, to the extent that they influence membrane composition, may have important regulatory roles. Also, recent evidence suggests that both postprandial and fasting lipoproteins may be associated with either factor levels or activation state or both. This issue has added importance because several hemostatic and fibrinolytic factors are known CVD risk factors. Although there are associations between fasting lipid levels and several coagulation and fibrinolytic factors, the mechanisms are unclear, as are the implications for intervention. In general, postprandial lipids are at least somewhat procoagulant because they activate factor VII. It remains to be demonstrated, however, that this postprandial activation has important clinical correlates. Dietary supplementation with marine omega-3 fatty acids does prolong the bleeding time and may decrease thrombotic potential; however, other than this, little is known about the direct effects of dietary fatty acids on hemostatic and fibrinolytic activities. Much work is needed in carefully controlled studies to expand our knowledge in this important area.

A high-trans fatty acid diet and insulin sensitivity in young healthy women

Epidemiological and experimental studies suggest that a diet rich in saturated fat affects insulin sensitivity. Monoenes and dienes that have an usaturated bond with the trans configuration (trans fatty acids) resemble saturated fatty acids with respect to structure, but no published data are available on the effect of trans fatty acids on insulin sensitivity. Therefore, the effects of diets high in trans fatty acids (TFA diet) and oleic acid (monounsaturated fat [MUFA] diet) on glucose and lipid metabolism were studied in 14 healthy women. Subjects consumed both experimental diets for 4 weeks according to a randomized crossover study design. Both experimental diet periods were preceded by consumption of a standardized baseline diet for 2 weeks. The diets provided 36.6% to 37.9% of energy (E%) as fat. In the TFA diet, there was 5.1 E% trans fatty acids, and in the MUFA diet, 5.2 E% oleic acid, substituted for saturated fatty acids in the baseline diet. A frequently sampled intravenous glucose tolerance test (FSIGT) was performed at the end of the experimental diet periods. Glucose effectiveness (S(G)) and the insulin sensitivity index (S(I)) did not differ after the two experimental diet periods. There was also no difference in the acute insulin response between the diets. The total cholesterol to high-density lipoprotein (HDL) cholesterol ratio and serum total triglyceride, HDL, and low-density lipoprotein (LDL) triglyceride and apolipoprotein B (apoB) concentrations were higher (P < .05) after the TFA diet. In conclusion, in young healthy women, the TFA diet resulted in a higher total/HDL cholesterol ratio and an elevation in triglyceride and apo B concentrations but had no effect on glucose and insulin metabolism compared with the MUFA diet.

Estimated intakes of trans fatty and other fatty acids in the US population

OBJECTIVE

To estimate mean level of trans fatty acid intakes using a representative sample of the US population.

DESIGN

The study used food intake data from the 1989-1991 Continuing Survey of Food Intakes by Individuals (CSFII) and the trans fatty acid contents of specific foods calculated from a database compiled by the US Department of Agriculture (USDA) to estimate the mean level and deciles of trans fatty acid intake of the representative US population.

SUBJECTS/SETTING

Trans fatty acid intakes were estimated for each subject (N = 11,258) in the CSFII data who completed both a 24-hour recall and a 2-day food record.

STATISTICAL ANALYSES PERFORMED

Weights developed by USDA for the survey were used for all data analyses. The Technical Assessment Systems (TAS) International Diet Research System (TAS-DIET), software developed by TAS, was used to derive weighted estimates of the mean and percentiles of the intake distribution. PC CARP, software designed by Iowa State University, was used to estimate standard errors.

RESULTS

Mean percentage of energy ingested as trans fatty acids was 2.6% and the mean percentage of total fat ingested as trans fatty acids was 7.4%. Across all age and gender groups examined, estimates ranged from 2.6% to 2.8% and 7.1% to 7.9%, respectively.

APPLICATIONS/CONCLUSIONS

Dietetics practitioners can use the representative data of this study to help clients achieve desired changes in consumption levels of trans fatty acids.

Functional food science and the cardiovascular system

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Similar effects of diets rich in stearic acid or trans-fatty acids on platelet function and endothelial prostacyclin production in humans

The effects of stearic acid (C18:0) and trans-fatty acids (trans-FAs) on measures of platelet function and prostacyclin (PGI2) production are poorly understood in humans. In this controlled dietary study, platelet function and endothelial PGI2 production were studied in healthy humans after they consumed diets rich in C18:0 or trans-FAs. For 5 weeks, 80 subjects consumed a baseline diet high in saturated FAs and were then switched to a diet containing 9.3% of energy as stearic acid or a diet containing 8.7 energy% as trans-FAs from hydrogenated vegetable oils for another 5 weeks. All diets contained 32.2 to 33.9 energy% fat, 14.6 to 15.8 energy% saturated plus trans-FAs, 12.2 to 12.5 energy% cis-monounsaturated, and 2.9 to 3.5 energy% polyunsaturated FAs. No significant differences between the C18:0 and trans-FA diets were found in the urinary excretion of 2,3-dinor-thromboxane B2 or 2,3-dinor-6-keto-prostaglandin F1alpha. In vitro production of thromboxane B2 by platelets as well as urinary excretion of beta-thromboglobulin were also similar after both diets. Collagen-induced in vitro aggregation was significantly enhanced after the C18:0 diet compared with the trans-FA diet (P=.02), whereas no differences between the diets were found with ADP. The results indicate similar effects of C18:0 and trans-FA diets on platelet activation and endothelial PGI2 production.