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Garlic -- abstracts |
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Date:
May 12, 2005 12:18 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic and Cancer. A Critical Review of the Epidemiologic...
Garlic and Cancer. A Critical Review of the Epidemiologic Literature
Author:
Fleischauer AT, Arab L
Source:
J Nutr. 2001;131:1032S-1040S.
Abstract:
Animal and in vitro studies provide evidence of an anticarcinogenic effect of active ingredients in garlic. This review of the epidemiologic literature on garlic consumption addresses cancers of the stomach, colon, head and neck, lung, breast and prostate. Nineteen studies reported relative risk estimates for garlic consumption and cancer incidence. Site-specific case-control studies of stomach and colorectal cancer, in which multiple reports were available, suggest a protective effect of high intake of raw and/or cooked garlic. Cohort studies confirm this inverse association for colorectal cancer. Few cohort and case-control studies for other sites of cancer exist. Garlic supplements, as analyzed in four cohort studies and one case-control report, from two distinct populations, do not appear to be related to risk. Low study power, lack of variability in garlic consumption categorization within studies and poor adjustment for potential cofounders may limit the reliability of any conclusions regarding garlic supplements. However, an indication of publication bias was also found by visual inspection of a funnel plot and in a log-rank test (P = 0.004). Evidence from available studies nevertheless suggests a preventive effect of garlic consumption in stomach and colorectal cancers. The study limitations indicate the need for more definitive research and improved nutritional epidemiologic analyses of dietary data.
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Date:
May 12, 2005 12:20 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic as a Lipid Lowering Agent-A Meta-Analysis
Garlic as a Lipid Lowering Agent-A Meta-Analysis
Author:
Silagy C, Neil A
Source:
Journal of the Royal College of Physicians of London. 1994; 28(1):39-45.
Abstract:
Garlic supplements may have an important role to play in the treatment of hypercholesterolaemia. To determine the effect of garlic on serum lipids and lipoproteins relative to placebo and other lipid lowering agents, a systematic review, including meta-analysis, was undertaken of published and unpublished randomized controlled trials of garlic preparations of at least four weeks duration. Studies were identified by a search of MEDLINE and the ALTERNATIVE MEDICINE electronic databases, from references listed in primary and review articles, and through direct contact with garlic manufacturers. Sixteen trials, with data from 952 subjects, were included in the analyses. Many of the trials had methodological shortcomings. The pooled mean difference in the absolute change from baseline to final measurement in mmol/l) of total serum cholesterol, triglycerides, and high-density lipoprotein (HDL)-cholesterol was compared between subjects treated with garlic therapy against those treated with placebo or other agents. The mean difference in reduction of total cholesterol between garlic-treated subjects and those receiving placebo (or avoiding garlic in their diet) was -0.77 mmol/l (95% CI: -0.65, -0.89 mmol/l). These changes represent a 12% reduction with garlic therapy beyond the final levels achieved with placebo alone. The reduction was evident after one month of therapy and persisted for at least six months. In the dried garlic powders, in which the allicin content is standardized, there was no significant difference in the size of the reduction across the dose range of 600-900 mg daily. Dried garlic powder preparations also significantly lowered serum triglyceride by 0.31 mmol/l compared to placebo (95% CI: -0.14, -0.49). HDL-cholesterol was non-significantly lowered by 0.04 mmol/l (95% CI: -0.11, 0.03 mmol/l). Side effects from garlic therapy, other than odor, were rare. In conclusion, use of garlic therapy, either as dried garlic preparations (in doses as low as 600 mg per day) or as fresh, high allicin yielding garlic (10-20 g per day) appears significantly to reduce total serum cholesterol over a 1-3 month period. However, more rigorously designed and analyzed trials are needed. --
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Date:
May 12, 2005 12:33 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Compounds Modulate Macrophage and T-Lymphocyte Functions
Garlic Compounds Modulate Macrophage and T-Lymphocyte Functions
Author:
Lau BH, Yamasaki T, Gridley DS
Source:
Mol Biother. 1991; 3(2):103-107.
Abstract:
Organosulfur compounds of garlic have been shown to inhibit growth of animal tumors and to modulate the activity of diverse chemical carcinogens. There is also evidence that garlic may modulate antitumor immunity. In this study, we determined the effects of an aqueous garlic extract and a protein fraction isolated from the extract on the chemiluminescent oxidative burst of the murine J774 macrophage cell line and thioglycollate-elicited peritoneal macrophages obtained from BALB/c mice. T-lymphocyte activity was determined using mouse splenocytes incubated with phytohemagglutinin, labeled with [3H]-thymidine and assayed for lymphoproliferation. Significant dose-related augmentation of oxidative burst was observed with garlic extract and the protein fraction. The protein fraction also enhanced the T-lymphocyte blastogenesis. The data suggest that garlic compounds may serve as biological response modifiers by augmenting macrophage and T-lymphocyte functions.
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Date:
May 12, 2005 12:34 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Consumption and Cancer Prevention...
Garlic Consumption and Cancer Prevention: Meta-Analyses of Colorectal and Stomach Cancers
Author:
Fleischauer AT, Poole C, Arab L
Source:
Am J Clin Nutr. 2000;72:1047-1052.
Abstract:
BACKGROUND: Animal and in vitro studies have provided evidence of an anticarcinogenic effect of active ingredients in garlic.
OBJECTIVE: The objective was to conduct meta-analyses of the epidemiologic literature on the association between garlic consumption and risk of stomach, colon, head and neck, lung, breast, and prostate cancers.
DESIGN: Meta-analyses were conducted for all cancers mutually and separately for colorectal and stomach cancers in relation to consumption of exclusively raw garlic, cooked garlic, or both (RC garlic). Eighteen studies reported a relative risk estimate for RC garlic consumption and cancer risk.
RESULTS: In the meta-analyses of colorectal and stomach cancer, the reference categories ranged from no consumption to consumption of 3.5 g/wk, whereas the highest categories ranged from any consumption to >28.8 g/wk. The average difference between the highest and lowest categories was 16 g/wk. The random-effects relative risk (RR) estimate of colorectal cancer and RC garlic consumption, excluding garlic supplements, was 0.69 (95% CI: 0.55, 0.89). For stomach cancer, the random effects RR estimate was 0.53 (95% CI: 0.31, 0.92). The heterogeneity among studies for the latter outcome (P = 0.0002) indicates the questionableness of the generalizability of this summary estimate. An indication of publication bias for all cancers combined is evident from a funnel plot of RC garlic consumption and cancer risk and from the results of the Begg and Mazumdar test (P = 0.049).
CONCLUSIONS: High intake of RC garlic may be associated with a protective effect against stomach and colorectal cancers. Heterogeneity of effect estimates, differences in dose estimation, publication bias, and possible alternative hypotheses (eg, confounding by total vegetable consumption) preclude sole reliance on summary effect estimates.
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Date:
May 12, 2005 12:39 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Elicits a Nitric Oxide-Dependent Relaxation and...
Garlic Elicits a Nitric Oxide-Dependent Relaxation and Inhibits Hypoxic Pulmonary Vasoconstriction in rats.
Author:
Kim-Park S, Ku DD.
Source:
Clin Exp Pharmacol Physiol 2000 Oct;27(10):780-786.
Abstract:
1. The aims of the present study were to determine the characteristics of garlic extract-induced relaxation in rat isolated pulmonary arteries, its susceptibility to changes in oxygen tension and its protective effect against hypoxic pulmonary vasoconstriction.
2. In normoxia, garlic extract (3-500 µ/mL) produced a dose- and nitric oxide (NO)-dependent relaxation. Following 60 min hypoxia, maximum garlic relaxation was reduced compared with control (mean (-SEM) -86 +/- 3 vs-69 +/- 2% of phenylephrine (PE) precontraction, respectively), but recovered after 60 min reoxygenation (-85 +/- 3% PE precontraction).
3. Acetylcholine (0.1 micromol/L)-induced NO-dependent relaxation was reduced from a control value of -76 +/- 1% to -46 +/- 4% during hypoxia and was further reduced to -35 +/- 2 % after reoxygenation.
4. In endothelium-intact arteries, hypoxic exposure resulted in a triphasic response: early transient contraction (+24 +/- 4%), followed by transient relaxation (-37 +/- 7%) and then sustained contraction (+62 +/- 5%).
5. Pretreatment with NG-nitro-L-arginine methyl ester abolished the early transient contraction, moderately attenuated the sustained contraction and had no effect on the transient relaxation. Mechanical endothelial disruption inhibited all hypoxia-induced vascular changes.
6. Garlic pretreatment had no effect on the early transient contraction (+25 +/- 4%), but inhibited the transient relaxation (-5 +/- 3%; P < 0.05) and the sustained contraction (+26 +/- 5%;P < 0.05).
7. Garlic also significantly inhibited endothelin-l-induced contractions in a dose-dependent manner.
8. These findings show that garlic extract modulates the production and function of both endothelium-derived relaxing and constricting factors and this may contribute to its protective effect against hypoxic pulmonary vasoconstriction.
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Date:
May 12, 2005 12:41 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Extract Modulation or Pulmonary Vascular Function:
Garlic Extract Modulation or Pulmonary Vascular Function: Comparisons Among Fresh, Aged, Freeze-dried Powder and Oil Macerate
Author:
Ku DD, Abdel-Razek TT, Dai J, Fallon MB, Abrams GA
Source:
FASEB Journal, 1998
Abstract:
Garlic has been advocated for a variety of therapeutic applications including pulmonary vasodiladon, but definitive experimental evidence supporting these claims remain inconclusive. We compared the relative vasorelaxation efficacv of fresh garlic extract (FG) to those commercially packaged garlics on rat pulmonary artery (PA) rings. Water extract of fresh whole garlic (1-500 µg/ml) produced a dose-dependent relaxation in endothelium (EC)-intact (PA, reaching a maximum of -62±4% (M±SE of 18 rings). Maximum relaxation observed with the garlic storage leaves (-79.±4%, n=16 rings) was significantly higher than the garlic inner stem (-48±5%, n=12 rings). Boiling of garlic extracts at l00ºC for 30 mins reduced the relaxation by 10-20%. Mechanical disruption of EC or pretreatment with L-NAME, reduced the relaxation by 30-40%. Extracts from freeze-dried powder (Garliquc; Pure-Gar and Kwai), aged garlic (Garlique), and garlic oil macerate (Softgel) resulted in -87±3% (n=16 rings), -72±6% (n=30 rings), -45±3% (n=30 rings), -22±5% (n=14 rings) and -5±3% (n=14 rings relaxation, respectively. Vasoinhibitory effect of FG extract was readily reversible upon washing, whereas the Pure-Gar and Garlique effects tended to be longer lasting and PA contractile response remained depressed even after 60-min washing. These results show that extracts of both fresh and freeze-dried garlic, but not the oil macerate, are capable eliciting both EC-dependent and -independent relaxation in rat PA. Differences in vasorelaxant potency may be related to the concentrations of the garlic active ingredient, allicin, in different garlic preparations.
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Date:
May 12, 2005 12:44 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic for Treating Hypercholesterolemia - A Meta-Analysis ...
Garlic for Treating Hypercholesterolemia - A Meta-Analysis of Randomized Clinical Trials
Author:
Stevinson C, Pittler MH, Ernst E
Source:
Ann Intern Med. 2000;133:420-429.
Abstract:
PURPOSE: To investigate the effect of garlic on total cholesterol level in persons with elevated levels by conducting a meta-analysis of randomized, double-blind, placebo-controlled trials.
DATA SOURCES: Systematic literature searches were conducted on the MEDLINE, EMBASE, BIOSIS, Cochrane Library, AMED, and CISCOM databases. Manufacturers of commercial garlic preparations and experts in the field were asked about published or unpublished trials.
STUDY SELECTION: Selected trials were required to state that they were randomized, double-blind, and placebo-controlled; use garlic monopreparations; include persons with mean total cholesterol levels of at least 5.17 mmol/L (200 mg/dL); and report total cholesterol level as an end point. There were no language restrictions.
DATA EXTRACTION: Two reviewers, blinded to key identifiers of each paper, independently extracted data in a standardized manner and assessed methodologic quality by using the Jadad scale. Discrepancies were settled through discussion.
DATA SYNTHESIS: In the 13 trials included in the meta-analysis, garlic reduced total cholesterol level from baseline significantly more than placebo (P < 0.01); the weighted mean difference was -0.41 mmol/L (95% CI, -0.66 to -0.15 mmol/L) (-15.7 mg/dL [CI, -25.6 to -5.7 mg/dL]). Six diet-controlled trials with the highest scores for methodologic quality revealed a nonsignificant difference between garlic and placebo groups; the weighted mean difference was -0.11 mmol/L (CI, -0.30 to 0.08 mmol/L) (-4.3 mg/dL [CI, -11.7 to 3.1 mg/dL]).
CONCLUSIONS: The available data suggest that garlic is superior to placebo in reducing total cholesterol levels. However, the size of the effect is modest and the robustness of the effect is debatable. The use of garlic for hypercholesterolemia is therefore of questionable value.
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Date:
May 12, 2005 12:45 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Inhibits Free Radical Generation and ...
Garlic Inhibits Free Radical Generation and Augments Antioxidant Enzyme Activity in Vascular Endothelial Cells
Author:
Wei Z, Lau BHS
Source:
Nutrition Research. 1998; 18(1):61-70.
Abstract:
Oxygen free radicals have been implicated in mediating various pathological processes such as ischemia, inflammatory diseases, diabetes, and atherosclerosis. The antioxidant enzymes - superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) - play an important role in scavenging oxidants and preventing cell injury. Aged Garlic Extract (AGE) has been shown to prevent oxidant-induced injury of endothelial cells. The present study determined the effects of AGE on the generation of hydrogen peroxide (H2O2) and superoxide anion (O2-) and the activity of three antioxidant enzymes in bovine pulmonary artery endothelial cells (PAEC). Confluent monolayers of PAEC were incubated with AGE, and oxidative stress was triggered by hypoxanthine and xanthine oxidase or H2O2. AGE exhibited both concentration- and time-dependent suppression of H2O2 and O2- generation, and it also significantly increased the activities of SOD, CAT and GPX The results suggest that AGE may be an effective antioxidant in preventing or treating disorders related to endothelial cell injury associated with free radicals.
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Date:
May 12, 2005 12:57 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Powder and Plasma Lipids and Lipoproteins...
Garlic Powder and Plasma Lipids and Lipoproteins: A Multicenter, Randomized, Placebo-Controlled Trial
Author:
Isaacsohn JL, Moser M, Stein EA, Dudley K, Davey JA, Liskov E, Black HR.
Source:
Arch Intern Med. 1998;158(11):1189-1194.
Abstract:
BACKGROUND: Garlic powder tablets have been reported to lower serum cholesterol levels. There is widespread belief among the general public that garlic powder tablets aid in controlling cholesterol levels. However, much of the prior data demonstrating the cholesterol-lowering effect of garlic tablets involved studies that were inadequately controlled.
OBJECTIVE: To determine the lipid-lowering effect of garlic powder tablets in patients with hypercholesterolemia.
METHODS: This was a randomized, double-blind, placebo-controlled, 12-week, parallel treatment study carried out in 2 outpatient lipid clinics. Entry into the study after 8 weeks of diet stabilization required a mean low-density lipoprotein cholesterol level on 2 visits of 4.1 mmol/L (160 mg/dL) or lower and a triglyceride level of 4.0 mmol/L (350 mg/dL) or lower. The active treatment arm received tablets containing 300 mg of garlic powder (Kwai) 3 times per day, given with meals (total, 900 mg/d). This is equivalent to approximately 2.7 g or approximately 1 clove of fresh garlic per day. The placebo arm received an identical-looking tablet, also given 3 times per day with meals. The main outcome measures included levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol after 12 weeks of treatment.
RESULTS: Twenty-eight patients (43% male; mean +/- SD age, 58 +/- 14 years) received garlic powder treatment and 22 (68% male; mean +/- SD age, 57 +/- 13 years) received placebo treatment. There were no significant lipid or lipoprotein changes in either the placebo- or garlic-treated groups and no significant difference between changes in the placebo-treated group compared with changes in the garlic-treated patients.
CONCLUSION: Garlic powder (900 mg/d) treatment for 12 weeks was ineffective in lowering cholesterol levels in patients with hypercholesterolemia.
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Date:
May 12, 2005 12:58 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Powder Tablets Reduce Atherogenicity of Low Density Lipo-
Garlic Powder Tablets Reduce Atherogenicity of Low Density Lipoprotein. A Placebo-Controlled Double-Blind Study.
Author:
Orekhov AN
Source:
Nutrition and Metabolism and Cardiovascular Disease. 1996; 6:21-31.
Abstract:
In a placebo-controlled double-blind trial of 23 subjects with coronary artery disease who had 1 to 3 major coronary arteries that were 75% blocked or higher, 300 mg of garlic powder from 1 Kwai tablet, 2 and 4 hours after a single dose, showed the atherogenicity of the patients sera to be markedly decreased. There was less cholesterol accumulation in human aortic smooth muscle cells cultured with patients sera after treatment compared with those cultured with sera obtained prior to the administration of the garlic. After 3 weeks of long-term Kwai therapy at 300 mg, 3 times daily, blood serum atherogenicity was significantly lower compared with initial levels. A two-fold decrease in atherogenicity was recorded 4 weeks after Kwai therapy. Long-term therapy lowered the atherogenicity of LDL isolated from patients plasma. The atherogenicity of LDL isolated 2 hours after a single dose of Kwai did not change and remained unchanged during 7 days of therapy. The ability of LDL to induce intracellular cholesterol accumulation was decreased by 38% on the 28th day of therapy. The ability of LDL to stimulate proliferation of cultured cells was also decreased as a result of long-term therapy with Kwai. Atherogenic LDL isolated from patients had a lower content of sialic acid compared with native LDL of healthy subjects. The sialic acid content of LDL did not change after single-dose administration and after 7 days of therapy. At the end of the 28 days of therapy, the sialic acid content of LDL was significantly higher than at the beginning of therapy. The authors believe that the decrease in LDL atherogenicity by garlic powder tablets was due to increased sialic acid content rather than a decreased susceptibility to LDL oxidation.
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Date:
May 12, 2005 12:59 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Prevents Hypertension Induced by Chronic Inhibition ...
Garlic Prevents Hypertension Induced by Chronic Inhibition of Nitric Oxide Synthesis.
Author:
Pedraza-Chaverri J, Tapia E, Medina-Campos ON, de los Angeles Granados M, Franco M
Source:
Life Sci. 1998;62(6):PL 71-77.
Abstract:
It has been reported that garlic activates nitric oxide synthase in vitro and that chronic inhibition of nitric oxide (NO) synthesis by N omega-nitro-L-arginine-methyl-ester (L-NAME) induces arterial hypertension in rats. In this work, we studied the effect of oral administration of L-NAME for 4 weeks on control and garlic-fed rats. Basal systolic blood pressure was recorded 4 weeks after garlic supplementation, and on weeks 1, 2, 3, and 4 after L-NAME treatment. At the end of the study, the in vivo NO production was evaluated indirectly by measuring the urinary excretion of the stable end products of NO metabolism, nitrite (N02-) and nitrate (N03-). It was found that L-NAME induced arterial hypertension on weeks 1-4 in control rats but not in garlic-fed rats, whose blood pressure remained essentially as the basal values. Also, during this time period, blood pressure remained unchanged in garlic-fed rats without L-NAME treatment. Urinary excretion of N02-/NO3- decreased in L-NAME-treated rats, increased in garlic-fed rats, and remained unchanged in garlic-fed rats treated with L-NAME. It was concluded that garlic blocks the L-NAME -induced hypertension by antagonizing in vivo the inhibitory effect of L-NAME on NO production.
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Date:
May 12, 2005 01:01 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Supplementation and Lipoprotein Oxidation Susceptibility
Garlic Supplementation and Lipoprotein Oxidation Susceptibility
Author:
Phelps S, Harris W
Source:
LIPIDS. 1993; 28(5):475-477.
Abstract:
Interventions which make serum lipoproteins less susceptible to oxidation may be antiatherogenic. The antioxidant properties of garlic which have been demonstrated in vitro led us to investigate the effects of garlic supplements on lipoprotein oxidation susceptibility in humans. Ten healthy volunteers were given 600 mg/d of garlic powder (6 tablets of Kwai) for two weeks in a placebo-controlled, randomized, double-blind crossover trial. We found that although serum lipid and lipoprotein levels were not lowered in this short time period, the ex vivo susceptibility of apolipoprotein B-containing lipoproteins to oxidation was significantly decreased (34%). Because garlic has been reported to beneficially affect serum lipid levels, platelet function, fibrinolysis and blood pressure, this additional effect of retarding lipoprotein oxidation may contribute to the potential antiatherosclerotic effect of garlic.
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Date:
May 12, 2005 01:08 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic Supplements...
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Date:
May 12, 2005 12:19 PM
Author: Darrell Miller
(dm@vitanetonline.com)
Subject: Garlic and Cardiovascular Disease
Garlic and Cardiovascular Disease
Author:
Loy MH, Rivlin RS
Source:
Nutr Clin Care. 2000;3:145-152.
Abstract:
The goal of this review is to evaluate the current status of knowledge concerning cardiovascular effects of allium derivatives from garlic and to identify potential areas of future research. To date, the cardiovascular actions most studied include lipoprotein metabolism, hypertension, thrombosis, and antioxidant capacity. There are also some preliminary findings suggesting that garlic may lower elevated serum levels of homocysteine. Epidemiological, clinical, and laboratory studies have reported that garlic contains many biologically and pharmacologically active compounds. The majority of studies show that garlic lowers total serum cholesterol and LDL-cholesterol; inhibition of HMG-CoA reductase or squalene epoxidase appears to be the major mechanism. Lowering of blood pressure likely results from inhibition of angiotensin-converting enzyme activity. Antithrombosis effects may be related to inhibition of adenosine deaminase. Antioxidant effects may be related to the inhibition of lipoxygenase. The published studies in their aggregate suggest that appropriate usage of allium derivatives from garlic may potentially play a role in the maintenance of optimal cardiac function. Further research is needed to examine the structure-function relationships of the various allium derivatives of garlic, the amounts in foods and supplements required for efficacy, and the possible effects of combining garlic with other nutrients and medications. The mechanisms of action of allium derivatives on various aspects of cardiac function require further clarification.
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