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P L Zock

Publications and source records attributed to P L Zock.

At least 19 recordsLinked to original sources
PubMed2004

Bioavailability and antioxidant effects of olive oil phenols in humans: a review.

OBJECTIVE: We reviewed the bioavailability and antioxidant effects of phenols from extra virgin olive oil. SEARCH STRATEGY: We searched the MEDLINE database for the years 1966-2002. To review the bioavailability of olive oil phenols, we selected animal and human studies that studied the absorption, metabolism, and urinary excretion of olive oil phenols. We also estimated the intake of the various phenols in the Mediterranean area. To review the antioxidant effects of olive oil phenols, we included human and animal studies on the effect of olive oil phenols on markers of oxidative processes in the body. We excluded studies without a proper control treatment and studies in which the antioxidant effects of phenols could not be disentangled from those of the fatty acid composition of olive oil. RESULTS: Bioavailability studies in humans show that the absorption of olive oil phenols is probably larger than 55-66 mol%, and that at least 5% is excreted in urine as tyrosol and hydroxytyrosol. Animal studies suggest that phenol-rich olive oil lowers oxidisability of ex vivo low-density lipoprotein (LDL) particles or lowers markers in urine of oxidative processes in the body. In five out of seven human studies, however, these effects of phenols were not found. There are no data on the phenol concentrations in plasma that are attainable by intake of olive oil. We estimated that 50 g of olive oil per day provides about 2 mg or approximately 13 micromol of hydroxytyrosol-equivalents per day, and that the plasma concentration of olive oil phenols with antioxidant potential resulting from such an intake can be at most 0.06 micromol/l. This is much lower than the minimum concentrations of these phenols (50-100 micromol) required to show antioxidant activity in vitro. CONCLUSION: Although phenols from olive oil seem to be well absorbed, the content of olive oil phenols with antioxidant potential in the Mediterranean diet is probably too low to produce a measurable effect on LDL oxidisability or other oxidation markers in humans. The available evidence does not suggest that consumption of phenols in the amounts provided by dietary olive oil will protect LDL against oxidative modification to any important extent.

Animals↗
PubMed2004

Intake of n-3 fatty acids from fish does not lower serum concentrations of C-reactive protein in healthy subjects.

OBJECTIVE: High-sensitivity C-reactive protein (CRP), a marker of systemic inflammation, is a powerful predictor of cardiovascular risk. We hypothesised that n-3 fatty acids reduce underlying inflammatory processes and consequently CRP concentrations in healthy middle-aged subjects. DESIGN: Placebo-controlled, double-blind study. SUBJECTS: A total of 43 men and 41 postmenopausal women aged 50-70 y. Before and after intervention, we measured serum CRP concentrations with an enzyme immunoassay. INTERVENTIONS: Capsules with either 3.5 g/day fish oil (1.5 g/day n-3 fatty acids) or placebo for 12 weeks. RESULTS: The median CRP change in the fish oil group did not significantly differ from that in the placebo group (0.01 vs -0.17 mg/l, P = 0.057). CONCLUSION: The currently available data--including ours--do not support that beneficial effects on CRP are involved in a mechanism explaining the protective effect on heart disease risk of n-3 fatty acids as present in fish.

Aged↗
PubMed2003

Rationale and design of a randomised controlled clinical trial on supplemental intake of n-3 fatty acids and incidence of cardiac arrhythmia: SOFA.

BACKGROUND: Evidence from earlier studies indicates that intake of very long-chain n-3 polyunsaturated fatty acids (n-3 PUFA, also named omega-3 fatty acids) as present in fish oil reduces the risk of sudden death. Sudden death forms a major part of mortality from cardiovascular disease and is in most cases a direct consequence of cardiac arrhythmia. n-3 PUFA may exert their protective effect through reducing the susceptibility for cardiac arrhythmia. OBJECTIVE: To investigate the effect of n-3 PUFA on the incidence of recurrent ventricular arrhythmia. This paper presents the rationale, design and methods of the Study on Omega-3 Fatty acids and ventricular Arrhythmia (SOFA) and discusses problems encountered in conducting a multicentre clinical trial on food. DESIGN: A randomised, parallel, placebo-controlled, double blind intervention study, which obeys the guidelines for Good Clinical Practice. SETTING: Multiple cardiology centres in Europe. SUBJECTS: A total of 500 patients with an implantable cardioverter defibrillator (ICD). An ICD detects, treats and stores cardiac arrhythmic events in its memory chip. INTERVENTIONS: Patients receive either 2 g/day of fish oil, containing approximately 450 mg eicosapentaenoic acid and 350 mg docosahexaenoic acid, or placebo for 12 months. PRIMARY OUTCOME: Spontaneous ventricular tachyarrhythmias as recorded by the ICD or all-cause mortality. CONCLUSION: SOFA is designed to answer the question whether intake of n-3 PUFA from fish-a regular food ingredient-can reduce the incidence of life-threatening cardiac arrhythmia. If this proves to be true, increasing the intake of n-3 PUFA could be an easy, effective and safe measure to prevent fatal arrhythmia in the general population.

Anti-Arrhythmia Agents↗
PubMed2002

[Nutrition and health--fish fatty acids against fatal coronary heart disease].

There are strong indications that eating (fatty) fish or n-3 fatty acids from fish reduces the risk of fata coronary heart disease (CHD). Observational studies in the general population show that consumption of moderate amounts of fish or n-3 fatty acids from fish are associated with a lower risk of fatal coronary heart disease and in particular sudden cardiac death. The most plausible hypothesis is that n-3 fatty acids reduce the risk of CHD mortality via anti-arrhythmic effects. Two clinical intervention trials show that prescription of fish or n-3 fatty acids to patients with prior myocardial infarction is effective in preventing mortality due to CHD. Ongoing trials will have to prove the effectiveness of a low dose of n-3 fatty acids and show that the underlying mechanism involves a protective effect against life-threatening arrhythmias. In addition to other recommendations for a healthier diet and lifestyle, consumption of one or two fatty fish meals a week is a highly effective and safe measure to reduce CHD mortality in both the general population and patients.

Animals↗
PubMed2002

ATP binding cassette G5 C1950G polymorphism may affect blood cholesterol concentrations in humans.

ATP binding cassette protein G5 (ABCG5) and G8 (ABCG8) may be involved in the regulation of intestinal cholesterol absorption. Therefore, genetic variation at these loci may affect blood cholesterol concentrations by influencing dietary responsiveness. We studied the association between the ABCG5 C1950G (Gln640Glu) polymorphism and blood cholesterol concentrations in 486 subjects and responsiveness to dietary cholesterol in 99 participants in dietary trials. Mean baseline cholesterol concentrations were 0.65 +/- 0.22 mmol/l higher in 13 subjects with the G/G genotype than in 473 carriers of the C-allele (95% confidence interval 0.22-1.08 mmol/l). The response of serum total cholesterol to dietary cholesterol tended to be larger in subjects with the G/G genotype as compared with carriers of the C-allele. We suggest that the ABCG5 G/G genotype may increase serum cholesterol concentrations and, possibly responsiveness to dietary cholesterol in humans. Studies in other populations and experimental settings are required to confirm or reject this hypothesis.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2002

Apolipoprotein E polymorphism and serum lipid response to plant sterols in humans.

BACKGROUND: The apolipoprotein E polymorphism may influence the absorption of cholesterol from the intestine and thus the response of serum cholesterol to diet. We decided to use plant sterols to investigate this and studied whether the cholesterol-lowering effect of plant sterols differed between subjects with different apolipoprotein E genotyes. DESIGN: Thirty-one healthy subjects with the E3/4 or E4/4 genotype and 57 with the E3/3 genotype were fed sterol-enriched margarine or control margarine for 3 weeks each in a blind randomised cross-over design. The sterol margarine provided 3.2 g of plant sterols daily, was low-fat, and had the same fatty acid composition as the control margarine. Subjects used the margarines as part of their usual diet, which was fairly low in cholesterol (mean, 175 mg per day). The mean (+/- standard deviation) age of the subjects was 25 (+/- 11) years. RESULTS: The apolipoprotein E polymorphism did not significantly affect the responses of total and LDL cholesterol. The decrease in total cholesterol was 0.36 mmol L-1 (7.4%) in the E3/3 subjects and 0.31 mmol L-1 (5.7%) in the epsilon 4 subjects (P = 0.50) and that in LDL cholesterol was 0.34 mmol L-1 (12.2%) in the E3/3 subjects and 0.32 mmol L-1 (9.8%) in the epsilon 4 subjects (P = 0.68). CONCLUSION: The serum cholesterol response to plant sterols is not affected by the apolipoprotein E polymorphism in healthy subjects who consume a low-cholesterol diet.

Adult↗
PubMed2002

The decrease in body fat in mice fed conjugated linoleic acid is due to increases in energy expenditure and energy loss in the excreta.

We carried out energy balance studies in four groups of young, growing, 5-wk-old Balb-C mice (n = 12/group) that were either food restricted or nonrestricted and fed high fat diets (38 energy%) with or without 0.93 g/100 g conjugated linoleic acid (CLA) for 39 d. The energy in carcasses, excreta and food was measured in a bomb calorimeter. CLA lowered the percentage of the energy intake that was stored in the body from 1.9 +/- 0.8 to -2.3 +/- 0.7% (mean +/- SD, P < 0.05) in the nonrestricted mice and from 1.4 +/- 1.3 to -2.9 +/- 0.7% (P < 0.05) in the restricted mice. Thus, the CLA-treated mice had a net loss of body energy. The percentage of the energy intake eliminated in the excreta increased from 7.6 +/- 0.9% in controls to 8.7 +/- 1.0% (P < 0.05) in the CLA-treated mice that were nonrestricted and from 7.3 +/- 0.8 to 8.4 +/- 0.6 (P < 0.05) in the restricted mice. The amount of energy ingested minus the amount retained in carcasses and excreta equals the energy expenditure. The percentage of the energy intake that was expended as heat increased from 90.5 +/- 1.2 in controls to 93.6 +/- 1.5% (P < 0.05) in the CLA-treated nonrestricted mice and from 91.3 +/- 1.5 to 94.5 +/- 1.0% (P < 0.05) in the restricted mice. The lower energy storage in the CLA-fed mice was accounted for by an increase in the energy expenditure (74%) and by an increase in energy lost in the excreta (26%). Feeding CLA also increased liver weight, which may warrant further studies on the safety of CLA.

Adipose Tissue↗
PubMed2001

Apoprotein E genotype and the response of serum cholesterol to dietary fat, cholesterol and cafestol.

Previous studies on the effect of apoprotein E (APOE) polymorphism on the response of serum lipids to diet showed inconsistent results. We therefore studied the effect of apoprotein E polymorphism on responses of serum cholesterol and lipoproteins to various dietary treatments. We combined data on responses of serum cholesterol and lipoproteins to saturated fat, to trans-fat, to dietary cholesterol, and to the coffee diterpene cafestol with newly obtained data on the apoprotein E polymorphism in 395 mostly normolipidemic subjects. The responses of low-density lipoprotein (LDL-) cholesterol to saturated fat were 0.08 mmol/l larger in subjects with the APOE3/4 or E4/4 genotype than in those with the APOE3/3 genotype (95% confidence interval: -0.01-0.18 mmol/l). In contrast, responses of LDL-cholesterol to cafestol were 0.11 mmol/l smaller in subjects with the APOE3/4 or E4/4 genotype than in those with the APOE3/3 genotype (95% confidence interval: -0.29-0.07 mmol/l). Responses to dietary cholesterol and trans-fat did not differ between subjects with the various APOE genotypes. In conclusion, the APOE genotype may affect the response of serum cholesterol to dietary saturated fat and cafestol in opposite directions. However, the effects are small. Therefore, knowledge of the APOE genotype by itself may be of little use in the identification of subjects who respond to diet.

Adult↗
PubMed2001

Effect of phenol-rich extra virgin olive oil on markers of oxidation in healthy volunteers.

OBJECTIVE: We studied whether consumption of phenol-rich extra virgin olive oil affects the susceptibility of low density lipoproteins (LDL) to oxidation and other markers of oxidation in humans. DESIGN: Randomized cross-over intervention trial, stratified according to sex, age and energy intake. SETTING: Division of Human Nutrition and Epidemiology, Wageningen University, The Netherlands. SUBJECTS: Forty-six healthy men and women completed the study. INTERVENTION: Subjects consumed two diets supplying 69 g per day of extra virgin olive oil either rich or poor in phenols for 3 weeks each. The mean difference in phenol intake between the treatments was 18 mg per day. Vitamin E intake was low during the whole study. Fasting blood samples were taken twice at the end of each period. RESULTS: Resistance of LDL and high density lipoprotein (HDL) to oxidation was not affected by treatment. The mean lag time of copper-induced formation of conjugated dienes was 1.6 min shorter in LDL and 0.4 min longer in HDL after the high phenol diet. Other markers of antioxidant capacity in plasma were also not affected: mean lipid hydroperoxides were 0.07 micromol/l higher, mean malondialdehydes were 0.001 micromol/l higher, mean protein carbonyls were 0.001 nmol/mg protein lower, and the mean ferric reducing ability of plasma (FRAP) was 0.006 mmol/l higher after the high phenol diet. All 95% confidence intervals enclosed zero. Serum cholesterol concentrations were not affected by the treatment. CONCLUSION: Consumption of 18 mg per day of phenols from extra virgin olive oil for 3 weeks did not affect LDL or HDL oxidation or other markers of antioxidant capacity in fasting plasma samples.

Adolescent↗
PubMed2001

Genetic polymorphisms and lipid response to dietary changes in humans.

BACKGROUND: Previous studies on the effects of genetic polymorphisms on the serum cholesterol response to dietary treatments were often inconsistent and frequently involved small numbers of subjects. MATERIALS AND METHODS: We studied the effect of 10 genetic polymorphisms on the responses of serum cholesterol to saturated and trans fat, cholesterol and the coffee diterpene, cafestol, as measured in 26 dietary trials performed over 20 years in 405 mostly normolipidaemic subjects. RESULTS: Apoprotein A4 360-2 allele attenuated the response of low-density lipoprotein cholesterol to dietary cholesterol, but not in women. Subjects with the cholesteryl ester transfer protein TaqIb-1 allele had -0.02 to -0.05 mmol L-1 smaller responses of high-density lipoprotein cholesterol to diet than those with the 2/2 genotype. The effects of the other eight polymorphisms on cholesterol response were either inconsistent with results in previous studies or need to be replicated in other studies. CONCLUSIONS: Apoprotein A4360 and cholesteryl ester transfer protein TaqIb polymorphisms may affect dietary responses. However, no one single genotype was a major determinant of a subject's lipid response to diet. Therefore, knowledge of these genotypes by themselves is of little use in the identification of subjects who may or may not benefit from dietary treatment.

Adolescent↗
PubMed2001

Effect of consumption of phenols from olives and extra virgin olive oil on LDL oxidizability in healthy humans.

A high intake of olive oil has been proposed as an explanation for the low incidence of coronary heart disease in Mediterranean countries, but it is unclear whether olive oil offers specific benefits beyond a low content of saturated fat. Some types of extra virgin olive oil are rich in non-polar phenols, which might be taken up by plasma LDL particles and protect these from becoming atherogenic by oxidative modification. In a pilot study we found that consumption of 47 g fortified olive oil containing 31 mg phenols significantly increased the lag time of LDL oxidation from 112 +/- 5 min before to 130 +/- 7 min 2 h after the meal. However, this study was not controlled, and in the current study we therefore investigated whether olive oil phenols increase the lag time of LDL oxidation in postprandial samples when compared with a control group. Twelve healthy men and women consumed four different olive oil supplements with a meal on four separate occasions: one similar to the supplement in the pilot study (positive control); one containing mainly non-polar olive oil phenols; one containing mainly polar olive oil phenols; and one without phenols (placebo). Lag time significantly increased 2 h after the meals with the positive control (8 +/- 2 min), the polar phenols (8 +/- 2 min), and the placebo (8 +/- 2 min), but not after the non-polar phenols (-0.4 +/- 3 min). Increases were not statistically different between supplements. These results indicate that the lag time of LDL-oxidation is increased after consumption of a meal. This increase is probably due to non-specific meal or time effects and not to phenols from olives or olive oil. Furthermore, these findings stress the need for adequate controlled studies to avoid misinterpretations of the data.

Adult↗
PubMed2001

Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humans.

BACKGROUND: In population studies, high intakes of coffee are associated with raised concentrations of plasma homocysteine, a predictor of risk of cardiovascular disease. Chlorogenic acid is a major polyphenol in coffee; coffee drinkers consume up to 1 g chlorogenic acid/d. OBJECTIVE: We studied whether chlorogenic acid affects plasma total homocysteine concentrations in humans. For comparison we also studied the effects of black tea rich in polyphenols and of quercetin-3-rutinoside, a major flavonol in tea and apples. DESIGN: In this crossover study, 20 healthy men and women ingested 2 g (5.5 mmol) chlorogenic acid, 4 g black tea solids containing approximately 4.3 mmol polyphenols and comparable to approximately 2 L strong black tea, 440 mg (0.7 mmol) quercetin-3-rutinoside, or a placebo daily. Each subject received each of the 4 treatments for 7 d, in random order. RESULTS: Total homocysteine in plasma collected 4-5 h after supplement intake was 12% (1.2 micromol/L; 95% CI: 0.6, 1.7) higher after chlorogenic acid and 11% (1.1 micromol/L; 95% CI: 0.6, 1.5) higher after black tea than after placebo. Total homocysteine in fasting plasma collected 20 h after supplement intake was 4% (0.4 micromol/L; 95% CI: 0.0, 0.8) higher after chlorogenic acid and 5% (0.5 micromol/L; 95% CI: 0.0, 0.9) higher after black tea than after placebo. Quercetin-3-rutinoside did not significantly affect homocysteine concentrations. CONCLUSIONS: Chlorogenic acid, a compound in coffee, and black tea raise total homocysteine concentrations in plasma. Chlorogenic acid could be partly responsible for the higher homocysteine concentrations observed in coffee drinkers. Whether these effects on homocysteine influence cardiovascular disease risk remains to be established.

Adult↗
PubMed2001

Dietary cholesterol from eggs increases the ratio of total cholesterol to high-density lipoprotein cholesterol in humans: a meta-analysis.

BACKGROUND: Several epidemiologic studies found no effect of egg consumption on the risk of coronary heart disease. It is possible that the adverse effect of eggs on LDL-cholesterol is offset by their favorable effect on HDL cholesterol. OBJECTIVE: The objective was to review the effect of dietary cholesterol on the ratio of total to HDL cholesterol. DESIGN: Studies were identified by MEDLINE and Biological Abstracts searches (from 1974 to June 1999) and by reviewing reference lists. In addition, we included data from a more recently published study. Studies were included if they had a crossover or parallel design with a control group, if the experimental diets differed only in the amount of dietary cholesterol or number of eggs and were fed for > or =14 d, and if HDL-cholesterol concentrations were reported. Of the 222 studies identified, 17 studies involving 556 subjects met these criteria. RESULTS: The addition of 100 mg dietary cholesterol/d increased the ratio of total to HDL cholesterol by 0.020 units (95% CI: 0.010, 0.030), total cholesterol concentrations by 0.056 mmol/L (2.2 mg/dL) (95% CI: 0.046, 0.065 mmol/L; 1.8, 2.5 mg/dL), and HDL-cholesterol concentrations by 0.008 mmol/L (0.3 mg/dL) (95% CI: 0.005, 0.010 mmol/L; 0.2, 0.4 mg/dL). CONCLUSIONS: Dietary cholesterol raises the ratio of total to HDL cholesterol and, therefore, adversely affects the cholesterol profile. The advice to limit cholesterol intake by reducing consumption of eggs and other cholesterol-rich foods may therefore still be valid.

Cholesterol↗
PubMed2001

Dietary fats and cancer.

The present review addresses the evidence for a possible link between dietary fat and cancer. International comparisons suggest that a high-fat diet may increase cancer risk, and this hypothesis is supported by animal experiments. However, epidemiological studies within populations show little or inconsistent associations. Taken together, the available evidence for a relation between dietary fat and cancer is weak.

Animals↗
PubMed2000

Heavy coffee consumption and plasma homocysteine: a randomized controlled trial in healthy volunteers.

BACKGROUND: An elevated plasma concentration of total homocysteine is considered to be a strong risk factor for cardiovascular disease. Heavy coffee drinking has been related to high homocysteine concentrations in epidemiologic studies and in one experiment in which healthy subjects drank unfiltered, boiled coffee. OBJECTIVE: Our goal was to determine whether daily consumption of paper-filtered coffee raises plasma concentrations of total homocysteine in healthy subjects. DESIGN: Twenty-six volunteers (18-53 y of age) consumed 1 L/d of paper-filtered coffee brewed with 70 g regular ground beans or no coffee for 4 wk each in a randomized, crossover design. RESULTS: The mean (+/-SD) plasma concentration of total homocysteine in fasting blood was 8.1 +/- 1.8 micromol/L after abstention from coffee and 9.6 +/- 2.9 micromol/L after 3-4 wk of coffee drinking, a difference of 1.5 micromol/L (95% CI: 0.9, 2.1 micromol/L) or 18% (P: < 0.001). Coffee increased homocysteine concentrations in 24 of 26 individuals. Circulating concentrations of vitamin B-6, vitamin B-12, and folate were unaffected. CONCLUSION: Drinking large quantities of paper-filtered coffee raises fasting plasma concentrations of total homocysteine in healthy individuals.

Adult↗
PubMed2000

Effect of plant sterols from rice bran oil and triterpene alcohols from sheanut oil on serum lipoprotein concentrations in humans.

BACKGROUND: Intake of unsaponifiable compounds from edible oils, such as plant sterols, can lower serum cholesterol concentrations in humans. However, little is known about effects of other chemically related unsaponifiables in edible oils, such as triterpene alcohols. OBJECTIVE: We studied the effects of plant sterols from rice bran oil and triterpene alcohols from sheanut oil on cholesterol concentrations in healthy, normolipemic volunteers. DESIGN: Twenty-eight men and 32 women consumed 29 g/d of 3 margarines for 3 wk each on a crossover, double-blind basis. A margarine based on sunflower oil was used as the control. Concentrates of plant sterols from rice bran oil or triterpene alcohols from sheanut oil were added to make 2 experimental margarines with the same fatty acid composition as the control margarine. RESULTS: Intake of 2.1 g plant sterols/d from rice bran oil decreased total cholesterol by 0.19 mmol/L (95% CI: -0.31, -0.07 mmol/L) and LDL cholesterol by 0.20 mmol/L (95% CI: -0.30, -0.10 mmol/L). HDL-cholesterol and triacylglycerol concentrations did not change significantly. Intake of 2.6 g triterpene alcohols/d from sheanut oil did not significantly affect lipoprotein concentrations in all subjects combined. CONCLUSIONS: We found that 2.1 g plant sterols/d from rice bran oil lowered serum total cholesterol by 5% and LDL cholesterol by 9% in normolipemic humans, whereas triterpene alcohols from sheanut oil did not significantly affect lipoprotein concentrations in all subjects combined. The effect of rice bran oil sterols is probably due to ss-sitosterol and other 4-desmethylsterols and not to 4,4'-dimethylsterols.

Adolescent↗