Exchange of Microbiomes in Plant-Insect Herbivore Interactions.

Prokaryotic and eukaryotic microbial symbiotic communities span through kingdoms. The vast microbial gene pool extends the host genome and supports adaptations to changing environmental conditions. Plants are versatile hosts for the symbionts, carrying microbes on the surface, inside tissues, and even within the cells. Insects are equally abundantly colonized by microbial symbionts on the exoskeleton, in the gut, in the hemocoel, and inside the cells. The insect gut is a prolific environment, but it is selective on the microbial species that enter with food. Plants and insects are often highly dependent on each other and frequently interact. Regardless of the accumulating evidence on the microbiomes of both organisms, it remains unclear how much they exchange and modify each other's microbiomes. In this review, we approach this question from the point of view of herbivores that feed on plants, with a special focus on the forest ecosystems. After a brief introduction to the subject, we concentrate on the plant microbiome, the overlap between plant and insect microbial communities, and how the exchange and modification of microbiomes affects the fitness of each host.

No effect on oxidative stress biomarkers by modified intakes of polyunsaturated fatty acids or vegetables and fruit.

Diet may both increase and decrease oxidative stress in the body. We compared the effects of four strictly controlled isocaloric diets with different intakes of polyunsaturated fatty acids (PUFA, 11 or 3% of energy) and vegetables and fruit (total amount of vegetables and fruit 516 or 1059 g/10 MJ) on markers associated with oxidative stress in 77 healthy volunteers (19-52 years). Plasma protein carbonyls (2-aminoadipic semialdehyde residues) and whole-body DNA and nucleotide oxidation (urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine excretion) tended to decrease in all treatment groups with no differences between the diets. The diets did not differ in their effects on red blood cell antioxidative enzyme activities, either. The results suggest that in healthy volunteers with adequate nutrient intakes, 6-week diets differing markedly in the amount of PUFA or vegetables and fruit do not differ in their effects on markers associated with oxidative stress.

Alpha-linolenic acid and marine long-chain n-3 fatty acids differ only slightly in their effects on hemostatic factors in healthy subjects.

The effects of alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) on hemostatic factors were compared. Healthy subjects (29 women and 17 men aged 20-44 y) received either linseed oil (average ALA intake: 5.9 g/d) or fish oil plus sunflower oil (average EPA + DHA intake: 5.2 g/d) for 4 wk. The supplemented amount of fat was 1.19 mg/kJ (1 g/200 kcal) calculated energy expenditure. Stability of habitual diets was monitored. Blood samples were collected at baseline, at the end of the experimental period, and after a 12-wk follow-up period. Different changes in the study groups were seen only in serum cholesterol and triacylglycerols, platelet fatty acid composition, and ADP-induced platelet aggregation. The treatments did not differ in their effects on collagen-induced platelet aggregation and thromboxane production, aggregation to the thromboxane A2 mimic I-BOP, urinary excretion of 11-dehydro-thromboxane B2 and beta-thromboglobulin, bleeding time, plasma fibrinogen concentration, antithrombin III activity, factor VII coagulant activity, or activity of plasminogen activator inhibitor 1. The results indicate that supplemented ALA from vegetable oil and EPA and DHA from a marine source have largely parallel effects on hemostatic factors.

Stearic acid, trans fatty acids, and dairy fat: effects on serum and lipoprotein lipids, apolipoproteins, lipoprotein(a), and lipid transfer proteins in healthy subjects.

To compare the effects on serum lipoproteins of stearic acid, trans fatty acids, and dairy fat, 80 healthy subjects consumed a dairy fat-based (baseline) diet for 5 wk, then an experimental diet high in either trans fatty acids (8.7% of energy; n = 40) or stearic acid (9.3% of energy; n = 40) for another 5 wk. All diets provided 32.2-33.9% of energy as fat, 14.6-15.8% as saturated plus trans fatty acids, 11.4-12.5% as cis-monounsaturated fatty acids, 2.9-3.5% as polyunsaturated fatty acids, and 200-221 mg cholesterol/10 MJ. Compared with the dairy fat diet, stearic acid and trans fatty acids decreased serum total cholesterol concentrations similarly (by 13% and 12%, respectively, P < 0.001) but the trans fatty acid diet decreased HDL cholesterol (17%) and apolipoprotein (apo) A-I (15%) significantly more than did the stearic acid diet (11% and 12%, respectively). Stearic acid but not trans fatty acids reduced concentrations of LDL cholesterol and apo B significantly (P < 0.001). The trans fatty acid diet increased the ratio of LDL to HDL cholesterol (19%) and of apo B to apo A-I (16%) more than did the dairy fat diet (P < 0.001) but the stearic acid diet had no effect. Lipoprotein(a) concentrations increased with both experimental diets, significantly more with trans fatty acids (30%) than with stearic acid (10%). In conclusion, high amounts of trans fatty acids had more adverse effects on lipoproteins than did equal amounts of stearic acid and dairy fat. Stearic acid reduced LDL cholesterol, did not affect the ratio of LDL to HDL cholesterol, and increased lipoprotein(a), although to a lesser extent than did trans fatty acids. Dietary fats low in both saturated fatty acids and trans fatty acids should be favored.

Effect of dietary fat on blood pressure in a rural Finnish population.

Thirty couples living in Liperi, a community of North Karelia, aged 40 to 50 yr participated in a dietary intervention study to assess the influence of dietary fat on blood pressure and other parameters. After a weeklong base-line period the subjects consumed a low fat diet (24% of energy) with a polyunsaturated/saturated fat ratio (P/S) of 1.2 for 6 wk. After this 6-wk intervention period the subjects resumed their normal diets (36% energy from fat, P/S 0.15) for an additional 6-wk period. Body weight remained constant throughout the study and salt intakes were approximately 12 g/day. During the low fat, high P/S period a decrease of 7.5 and 2.8 mm Hg pressure occurred for systolic and diastolic blood pressure from the base-line level. When the normal diet was resumed, systolic and diastolic blood pressures increased by 7.7 and 6.3 mm Hg, respectively, from the levels observed at the end of the intervention period.

High dietary omega-6 polyunsaturated fatty acids drastically increase the formation of etheno-DNA base adducts in white blood cells of female subjects.

Lipid peroxidation generates reactive aldehydes such as trans-4-hydroxy-2-nonenal and malonaldehyde, which form promutagenic exocyclic DNA adducts in human cells and may contribute to diet-related cancers. Using ultrasensitive detection methods, analysis of WBC DNA from volunteers in a dietary study revealed that high intake of omega-6 polyunsaturated fatty acids increased malonaldehyde-derived adducts in male and female subjects. In contrast, etheno adducts (1,N6-ethenodeoxyadenosine; 3,N4-ethenodeoxycytidine) were not elevated in males but were, on average, 40 times higher in females, displaying a huge intersubject variation in lipid peroxidation-derived DNA damage. Exocyclic DNA adducts are promising biomarkers for examining the hypothesis of possible links between increased intake of dietary omega-6 polyunsaturated fatty acids, DNA damage, and elevated cancer risk for breast, colon, and prostate.

Coagulation and fibrinolysis factors in healthy subjects consuming high stearic or trans fatty acid diets.

The effects of stearic acid (C18:0) and trans fatty acids on variables related to coagulation and fibrinolysis were studied in 80 healthy humans average age 29 +/- 9 years. All subjects consumed a baseline diet high in saturated fatty acids, mainly from dairy fat for 5 weeks. After this baseline diet they were allocated either to a diet high (8.7% of energy, En%) in trans fatty acids from partially hydrogenated vegetable oil (40 subjects) or a diet high (9.3 En%) in stearic acid (40 subjects) for 5 weeks. All diets contained 32.2-33.9 En% fat, 14.6-15.8 En% saturated plus trans fatty acids, 12.2-12.5 En% cis-monounsaturated and 2.9-3.5 En% polyunsaturated fatty acids and 216-250 mg/10 MJ cholesterol. The fats were mixed into solid foods and almost all daily food was provided. In comparison with the baseline dairy fat diet no change was observed in the concentrations of plasma fibrin degradation products and D-dimers. Also the factor VII coagulant activity (F VII:C), tissue type plasminogen activity (tPA) and plasminogen activator inhibitor activity (PAI-1) were not affected by the experimental diets. Small increase in plasma fibrinogen concentration during the stearic acid diet was statistically significant (from 3.49 to 3.63 g/l: p = 0.041), but probably without any biological significance. Both diets increased plasma level of lipoprotein Lp(a). It can be concluded that as far as coagulation and fibrinolysis are concerned there is no need to differentiate between stearic acid or trans monoenoic fatty acids.

Comparison of the effects of two diets rich in monounsaturated fatty acids differing in their linoleic/alpha-linolenic acid ratio on platelet aggregation.

The effect of dietary linoleic/alpha-linolenic acid ratio on human platelet aggregation in vitro was investigated using low-erucic acid rapeseed oil and high-oleic acid sunflower oil as the major fat sources. In a cross-over study 20 healthy male subjects, average age 29 year (range 20-46 yr), followed experimental rapeseed oil (RO) and Trisun-sunflower oil (TSO) diets after their habitual diet for six weeks. Subjects were provided most of the fat containing foods but were allowed to eat other foods almost freely. Fatty acid compositions of the diets calculated from dietary records were as follows (saturated/monounsaturated/polyunsaturated fatty acids): RO diet 12.4/18.6/8.9% of total energy (en%) (linoleic/alpha-linolenic acid ratio 2.8) and TSO diet 11.8/17.8/8.3 en% (linoleic/alpha-linolenic acid ratio 28), respectively. Plasma cholesterol ester fatty acid composition proved compliance to the experimental diets. Platelet aggregations induced by ADP (1, 2 and 3 microM) or thrombin (0.12, 0.15 and 0.18 NIH/ml) were significantly enhanced and collagen-(1.5, 2.5 and 5.0 micrograms/ml) induced aggregation tended to be enhanced after the TSO diet compared with the RO diet. After the TSO diet platelet aggregation was enhanced from the level of the habitual diets by one thrombin (0.18 NIH/ml), one collagen (1.5 micrograms/ml) and all three ADP concentrations. The diets had no effect on antithrombin III activity. Results show that platelet aggregation in vitro decreases as the ratio of linoleic acid to alpha-linolenic acid decreases in diets rich in monounsaturated fatty acids.

Rapeseed oil and sunflower oil diets enhance platelet in vitro aggregation and thromboxane production in healthy men when compared with milk fat or habitual diets.

In this highly controlled trial, 26 normolipidemic men (average age 28 years, range 18 to 60) were fed a baseline diet high in milk fat (MF) (fat 36% of energy, saturates 19%, monounsaturates 11%, polyunsaturates 4%), followed by a diet high in sunflower oil (SO) (fat 38% of energy, saturates 13%, monounsaturates 10%, polyunsaturates 13%) and another diet high in low erucic-acid rapeseed oil (RO) (fat 38% of energy, saturates 12%, monounsaturates 16%, polyunsaturates 8%). All diets were mixed natural diets with the same cholesterol contents. The baseline milk fat diet was given for 14 days and the oil diets for 24 days in a blind cross-over design. The platelet in vitro aggregation (slope %/min) induced by 1, 2 and 3 microM ADP and collagen (25 micrograms/ml PRP) was highly significantly (p less than 0.001) increased after both oil diets when compared with the results from the milk fat diet. The aggregation pattern determined by threshold collagen concentration confirmed increased collagen sensitivity of the platelets after the rapeseed oil diet (p less than 0.001). The enhancement of platelet aggregation was associated with increased in vitro platelet thromboxane production after the oil diets vs. the milk fat diet (p less than 0.05 after the sunflower oil diet and p less than 0.001 after the rapeseed oil diet).

Replacement of dietary saturated by unsaturated fatty acids: effects of platelet protein kinase C activity, urinary content of 2,3-dinor-TXB2 and in vitro platelet aggregation in healthy man.

The present study was conducted to compare the effects of oleic (OA) and linoleic acids (LA) on platelet function in healthy subjects. After a 4-week period on a diet rich in saturated fatty acids (SAFA), 38 volunteers (20 female, 18 male) had a high OA (18.0 en%) diet or a high LA diet (11.5 en%) for four weeks in a controlled manner. A control group of 13 subjects consumed their habitual diet throughout the study. Replacing the SAFA diet by the OA or LA diet did not affect the membrane-associated activity of platelet protein kinase C (PKC). However, both diets tended to increase the cytosolic activity to a comparable extent. Both the OA and the LA diets increased urinary excretion of 2.3-dinor-TXB2, as compared to the SAFA diet, whereas the urinary excretion of beta-thromboglobulin remained unchanged. As compared to the initial SAFA diet, platelet aggregation to collagen increased after both diets, while ADP induced aggregation showed no diet-induced changes. The results indicate increased platelet activity after both oil diets with no differences between the OA and LA diet and confirm in vitro findings that cis-unsaturated fatty acids have a distinct effect on cytosolic PKC, in particular.

Chemopreventative activity of crude hydroxymatairesinol (HMR) extract in Apc(Min) mice [corrected].

We studied the effects of a lignan, hydroxymatairesinol (HMR), and rye bran on intestinal tumor development in adenomatous polyposis colimultiple intestinal neoplasia (Apc)(Min) mice. HMR showed a strong chemopreventive effect in this animal model. The mean number of adenomas in the small intestine was significantly lower (26.6+/-11.0, P<0.05) in mice fed the TNS tumor promoter insulin and HMR when compared with the insulin and insulin/rye bran fed mice (39.6+/-8.9 and 36.0+/-7.4, respectively). HMR resulted in normalization of beta-catenin levels in adenoma tissue, indicating that HMR mediates its chemopreventive effect through the Apc-beta-catenin pathway. In the cytosolic fraction, beta-catenin level in adenoma tissue was significantly elevated (P=0.008-0.013) in all the diet groups as compared with that of the surrounding mucosa. In the nuclear fraction, beta-catenin in the insulin (3.15+/-2.9 relative units) and insulin/rye (5.17+/-6.94 relative units) groups was also significantly higher (P=0.003-0.009) in the adenoma tissue when compared with the surrounding mucosa (0.5+/-0.5 and 0.35+/-0.39 relative units). However, HMR was able to restore nuclear beta-catenin level of the adenoma tissue (0.41+/-0.25 relative units) to the level found in the surrounding mucosa (0.36+/-0.28 relative units).

Protein kinase C activation in rat colonic mucosa after diets differing in their fatty acid composition.

We studied the effects of different types of dietary fats on fatty acid composition and activity of protein kinase C (PKC) in rat colonic mucosa. Activation of PKC, a key enzyme in signal transduction and growth regulation, provides a mechanism by which dietary components could be involved in colon carcinogenesis. Male Wistar rats (n = 12/group) were fed a semisynthetic high fat diet (43% of energy) containing either sunflower oil, rapeseed oil, or butter for 4 weeks ad libitum. The control group received a low fat sunflower oil diet (10% of energy). The butter diet increased membrane-associated PKC activity in rat colonic mucosa compared with the low fat control diet (1237 vs. 917 pmol/min per mg prot.; P = 0.028). Mucosal fatty acids reflected dietary fatty acid composition even though there was no clear association between the amount of mucosal fatty acids and PKC activity. More research is needed to elucidate how dietary fatty acids regulate colonic PKC activity.

Chemopreventive activity of crude hydroxsymatairesinol (HMR) extract in Apc(Min) mice.

We studied the effects of a lignan, hydroxymatairesinol (HMR), and rye bran on intestinal tumor development in adenomatous polyposis colimultiple intestinal neoplasia (Apc)(Min) mice. HMR showed a strong chemopreventive effect in this animal model. The mean number of adenomas in the small intestine was significantly lower (26. 6+/-11.0, P<0.05) in mice fed the inulin and HMR when compared with the inulin and inulin/rye bran fed mice (39.6+/-8.9 and 36.0+/-7.4, respectively). HMR resulted in normalization of beta-catenin levels in adenoma tissue, indicating that HMR mediates its chemopreventive effect through the Apc-beta-catenin pathway. In the cytosolic fraction, beta-catenin level in adenoma tissue was significantly elevated (P=0.008-0.013) in all the diet groups as compared with that of the surrounding mucosa. In the nuclear fraction, beta-catenin in the inulin (3.15+/-2.9 relative units) and inulin/rye (5.17+/-6.94 relative units) groups was also significantly higher (P=0.003-0.009) in the adenoma tissue when compared with the surrounding mucosa (0.5+/-0.5 and 0.35+/-0.39 relative units). However, HMR was able to restore nuclear beta-catenin level of the adenoma tissue (0.41+/-0.25 relative units) to the level found in the surrounding mucosa (0.36+/-0.28 relative units).

Lipid peroxidation status, somatic mutations and micronuclei in peripheral lymphocytes: a case observation on a possible interrelationship.

A controlled dietary study was conducted in healthy female volunteers and reported elsewhere [1]. In a subset of samples four different biomarkers were analyzed: plasma malondialdehyde (MDA) levels and urinary 8-isoprostaglandin-F(2alpha) were measured as markers for lipid peroxidation. The frequency of hprt (hypoxanthine guanine phosphoribosyl transferase) mutants and micronuclei in peripheral blood lymphocytes were analyzed as indicators of genotoxic effects. One of the ten individuals showed extremely high background levels in all of the four endpoints measured. This case observation raises the possibility that life style factors and dietary habits affect the level of DNA reactive lipid peroxidation products, which in turn increase mutagenic and cytogenetic effects. A possible association between these biomarkers, particularly in relation to dietary fat intake and antioxidant status, should now be studied in a larger trial.

Cis-unsaturated fatty acids and platelet function.

The main method to study platelet function in dietary studies has been the platelet aggregation test in vitro. Even though it is well established that dietary cis-unsaturated fatty acids (FAs) modify platelet aggregation some uncertainty still exists how to interpret the in vitro results in the context of a situation in vivo. The other ways to look at platelet activation are measurements of thromboxane metabolites in urine or the concentration of beta-thromboglobulin (betaTG) released from alpha-granules. Dietary fish oil or long-chain n-3 FAs lower the high basal excretion rate of thromboxane, while only a modest effect is noticed at a low basal excretion rate. Results on the effects of other cis-unsaturated FAs on urinary TXB2 metabolites are almost totally lacking. Furthermore, platelet betaTG release in vivo does not seem to be affected by changes in dietary FAs. The regulatory function of dietary FAs in platelets is extremely complex, and clearly more should be understood about the association between dietary FAs and platelet membrane FAs in connection with platelet responses to physiological stimuli and subsequent signal transduction inside the platelets.

A high linoleic acid diet increases oxidative stress in vivo and affects nitric oxide metabolism in humans.

Evidence from in vitro studies shows that increased intake of polyunsaturated fatty acids leads to increased oxidative stress, which may be associated with endothelial damage. We measured the urinary levels of 8-iso-PGF2alpha and nitric oxide metabolites as well as plasma sICAM-1 levels from healthy subjects after strictly controlled diets rich in either linoleic acid (LA, C18:2 n-6) or oleic acid (OA, C18:1 n-9). Thirty-eight volunteers (20 women and 18 men, mean age 27 years) consumed a baseline diet rich in saturated fatty acids (SFA) for 4 weeks and were then switched to either a high LA diet (11.5 en%) or a high OA diet (18.0 en%) also for 4 weeks. During the LA and OA diets, nearly all food was provided for the whole day. A control group of 13 subjects consumed their habitual diet throughout the study. Urinary excretion of 8-iso-PGF2alpha was significantly increased after the LA diet (170 vs 241 ng/mmol creatinine, P=0.04), whereas the urinary concentration of nitric oxide metabolites decreased (4.2 vs 2.6 mg/mmol creatinine, P=0.03). No significant changes were seen in the OA group. Significant differences between the LA and control group were found for both 8-oxo-PGF2alpha (P=0.03) and NO (P=0.02), whereas the OA and LA groups did not differ with respect to any parameter. Also plasma sICAM-1 remained unchanged in both groups throughout the study. In conclusion, the high-LA diet increased oxidative stress and affected endothelial function in a way which may in the long-term predispose to endothelial dysfunction.

A high-beef diet alters protein kinase C isozyme expression in rat colonic mucosa.

We recently reported that a red meat (beef) diet relative to a casein-based diet increases protein kinase C (PKC) activity in rat colonic mucosa. The purpose of this study was to further elucidate the effects of a high-beef diet on colonic intracellular signal transduction by analyzing steady-state protein levels of different PKC isozymes as well as activities of the three types of sphingomyelinases. Male Wistar rats (n = 12/group) were fed AIN93G-based diets either high in beef or casein for 4 weeks. Rats fed the beef diet had significantly (P < 0.05) higher cytosolic PKC alpha and lower membrane PKC delta protein levels than rats fed the casein diet. The beef-fed rats also had alterations in subfractions of PKC zeta/lambda so that they had a significantly (P = 0.001) lower level of membrane 70 & 75 kDa fraction and a higher (P = 0.001) level of cytosolic 40 & 43 kDa fraction than rats fed the casein diet. Because protein levels analyzed with a PKC zeta-specific antibody were similar, these differences in PKC zeta/lambda were probably due to changes in PKC lambda expression. PKC beta2 levels did not differ between the dietary groups. Diet had no significant effect on the activity of acid, neutral, or alkaline sphingomyelinase. This study demonstrated that consumption of a high-beef diet is capable of modulating PKC isozyme levels in rat colon, which might be one of the mechanisms whereby red meat affects colon carcinogenesis.

Dietary intervention study among 30 free-living families in Finland.

A dietary intervention study to reduce risk factors for coronary heart disease was carried out among 30 free-living middle-aged couples in North Karelia, Eastern Finland. During the study, the subjects changed their normal diet for six weeks. The main changes in the diet were decrease in the consumption of fat (from 39% to 24% of total calories), increase in the P:S ratio from 0.15 to 1.22, and increased consumption of fruit and vegetables. The changes in the food consumption pattern were facilitated by giving the families free food items, such as skim milk, vegetable margarine, vegetables, and fruit. The food consumption and nutrient intakes were measured by food consumption records kept every other day. Also, duplicate diets were collected once during each study period for chemical analysis. Compliance with the dietary changes was better than expected, and the acceptability and the palatability of the diet were reported to be good. The decrease in the fat content of the diet increased the nutrient density of the diet; i.e., the concentration of vitamins and minerals improved. This study showed how even more drastic dietary changes than those recommended by health authorities can be realized among ordinary Finnish people.

Comparison between dietary monounsaturated and polyunsaturated fatty acids as regards diet-related diseases.

We have studied the effects of dietary fatty acid (FA) composition on lipids and lipoproteins, platelet function and other hemostatic variables as well as on the endogenous formation of DNA adducts of malonaldehyde (MA) in healthy subjects in controlled dietary experiments. The FAs studied were monounsaturated oleic acid (OA, 18:1 n-9), n-6-polyunsaturated linoleic acid (LA, 18:2 n-6), n-3 polyunsaturated alpha-linolenic acid (ALA, 18:3 n-3), and two long-chain, n-3 polyunsaturated FAs, eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3). The results indicated that a high OA and high LA diet had comparable effects on lipids and lipoproteins when they replaced saturated FAs in a diet. Furthermore, the effect of ALA did not differ from that of LA in this respect. Both diets also similarly increased in vitro platelet aggregation when compared with high saturated FA baseline diet. In another study the effect of LA and ALA on platelet function was studied. In this study ALA decreased in vitro platelet aggregation when compared with LA. When ALA was compared with EPA + DHA it was found that platelet function and some coagulation and fibrinolysis parameters were mainly affected in a similar manner by ALA and EPA + DHA treatments. The high LA diet increased the levels of DNA adducts of MA when compared with the effect of the high OA diet. Our findings indicate that the interpretation of the effect of diet, dietary fat or a specific FA on the development of chronic disease is extremely complex.

Postprandial changes in platelet function and coagulation factors after high-fat meals with different fatty acid compositions.

OBJECTIVE: To compare the postprandial effects of three oils differing in their fatty acid composition on platelet aggregation and coagulation. The oils studied were low-erucic acid rapeseed oil (RO, oleic acid 54% of fatty acids), sunflower oil (SO, linoleic acid 64% of fatty acids) and butter oil (BO, saturated fatty acids 62% of fatty acids). DESIGN: The postprandial effects of three fat-loads were followed for 5 h. SETTING: Division of Nutrition, University of Helsinki. SUBJECTS: Twelve healthy female subjects (aged 23-38 years) were recruited among university students and employees. INTERVENTIONS: Postprandial lipaemia was induced by high-fat meals containing fat (RO, SO or BO) 1 g/kg of body weight, skim-milk powder, sugar, strawberries, and water. Each subject ingested each meal in three separate mornings after an overnight fast. The order of the meals was randomised. Blood samples were taken before and 1, 2.5, and 5 h after the test meal. RESULTS: All three test meals similarly affected platelet aggregation in platelet-rich plasma. Aggregation induced by collagen (0.6, 1 and 2.5 micrograms/ml) decreased during the 5-h period after the meals (P = 0.000). ADP-induced aggregation did not change during the follow-up period after any meal (P = 0.105-0.483). All fat loads increased factor VII coagulant activity (F VII:C) (P = 0.000), but in plasma fibrinogen concentration (P = 0.155) or antithrombin III activity (P = 0.278) no postprandial changes were found. CONCLUSIONS: These results show that high-fat meals have acute effects on platelet function and F VII:C in healthy women and that these effects are not mediated through the fatty acid composition of the meals.