Garlic Intake Research Articles

Raw Garlic Consumption and Risk of Liver Cancer: A Population-Based Case-Control Study in Eastern China.

Although the major risk factors for liver cancer have been established, preventive factors for liver cancer have not been fully explored. We evaluated the association between raw garlic consumption and liver cancer in a large population-based case-control study in Eastern China. The study was conducted in Jiangsu, China, from 2003 to 2010. A total of 2011 incident liver cancer cases and 7933 randomly selected population-controls were interviewed. Epidemiological data including raw garlic intake and other exposures were collected, and serum markers of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection were assayed. Overall, eating raw garlic twice or more per week was inversely associated with liver cancer, with an adjusted odds ratio (aOR) of 0.77 (95% confidence interval (CI): 0.62–0.96) compared to those ingesting no raw garlic or less than twice per week. In stratified analyses, high intake of raw garlic was inversely associated with liver cancer among Hepatitis B surface antigen (HBsAg) negative individuals, frequent alcohol drinkers, those having history of eating mold-contaminated food or drinking raw water, and those without family history of liver cancer. Marginal interactions on an additive scale were observed between low raw garlic intake and HBsAg positivity (attributable proportion due to interaction (AP) = 0.31, 95% CI: -0.01–0.62) and heavy alcohol drinking (AP = 0.28, 95% CI: 0.00–0.57). Raw garlic consumption is inversely associated with liver cancer. Such an association shed some light on the potential etiologic role of garlic intake on liver cancer, which in turn might provide a possible dietary intervention to reduce liver cancer in Chinese population.

Onion and Garlic Intake and Breast Cancer, a Case-Control Study in Puerto Rico

Studies show an inverse association between onion and garlic intake and risk of cancers of the lung, prostate, and stomach. There is limited evidence on the association between onion and garlic intake and breast cancer. We assessed this association in a population-based, case-control study in Puerto Rico. Incident, primary breast cancer cases (n = 314) were identified among women aged 30–79 from hospital and clinic records. Controls (n = 346) were women with no history of cancer other than nonmelanoma skin cancer, residents of the same area. Dietary intake was estimated using a food frequency questionnaire. Total onion and garlic intake included sofrito (a popular garlic- and onion-based condiment) intake frequency. Unconditional logistic regression assessed the association between onion and garlic consumption and breast cancer adjusting for age, education, parity, family history, body mass index, age at menarche, total energy, and smoking. Inverse associations with breast cancer were observed for moderate (OR (odds ratio) = 0.59, 95% CI (confidence interval): 0.35, 1.01) and high consumption (OR = 0.51, 95% CI: 0.30, 0.87) compared to low consumption of onion and garlic (Ptrend = 0.02). Results were similar when stratified by menopausal status. Study results suggest that high onion and garlic consumption is protective against breast cancer in this population.

Modulation of hydrogen sulfide gasotransmitter limits the proven benefits of garlic

Garlic has been used as a medicinal food for centuries. The biological activity of garlic relies on the presence of highly reactive sulfur compounds. Widespread in vitro and in vivo studies have reported the mechanism of action of the anticancer activity of garlic-derived organosulfur compounds (OSCs) in a wide range of cancer types. Moreover, epidemiological studies support an inverse correlation between garlic intake and cancer risk. More recently, several studies have reported the ability of garlic-derived OSCs to release hydrogen sulfide (H2S) and to affect H2S biosynthesis by altering specific H2S enzyme activity, such as cystathionine-beta-synthase or cystathionine-gamma-lyase. Paradoxically, some studies have reported that overexpression of H2S-producing enzymes is associated with ovarian and colon cancer progression. In this review, we aimed to provide a critical analysis of garlic anticancer activity by documenting our current understanding of the anticancer activity of garlic-derived OSCs. We propose here to raise a mechanistic gap in garlic-mediated anticancer activity by documenting our current knowledge of the role of H2S in cancer biology.

Allium vegetable consumption and health: An umbrella review of meta-analyses of multiple health outcomes.

Previously, our meta‐analysis and other studies have suggested that allium vegetable consumption is beneficial for health, but no umbrella review has been conducted to assess the evidence of the various health benefits of allium vegetable consumption. Therefore, we conducted this umbrella review on this topic. This umbrella review included a total of 16 meta‐analyses with 50 unique outcomes. The most beneficial cancer‐related outcome was shown for gastric cancer (risk ratio 0.78; 95% confidence interval [CI] 0.67–0.91). In addition, only 8 weeks of garlic consumption significantly decreased serum total cholesterol (weighted mean differences −17.20 mg/dl; 95% CI −23.10 to −11.30), and patients with dyslipidemia who consumed garlic experienced more benefits than the whole population. Diabetic patients with longer durations of garlic intake experienced more benefits in terms of fasting blood glucose (FBG), HbA1c, and serum fructosamine than healthy participants, and garlic intake was associated with blood pressure reduction in hypertensive patients but not in normotensive participants. Limited side effects of garlic, such as garlic odor and gastrointestinal complaints, were reported among the included meta‐analyses. Our results suggested that allium vegetables might be beneficial for cancer prevention. In particular, garlic was comparatively safe and is recommended as a long‐term dietary component for patients with dyslipidemia, diabetes, and hypertension.

Consumption of garlic and its interactions with tobacco smoking and alcohol drinking on esophageal cancer in a Chinese population.

Garlic consumption has been associated inversely with esophageal cancer (EC); however, its interactions with tobacco smoking and alcohol consumption have never been evaluated in an epidemiological study. We evaluated the potential interactions between garlic intake and tobacco smoking as well as alcohol consumption in a population-based case-control study with 2969 incident EC cases and 8019 healthy controls. Epidemiologic data were collected by face-to-face interviews using a questionnaire. The adjusted odds ratio (OR) and 95% confidence interval (CI) were estimated and additive and multiplicative interactions were evaluated using unconditional logistic regression models, adjusting for potential confounding factors. Semi-Bayes (SB) adjustments were used to reduce potential false-positive findings. EC was associated inversely with raw garlic intake [SB-adjusted OR for more than once a week=0.68, 95% CI: 0.57-0.80], with a strong dose-response pattern in the overall analysis and in the stratified analyses by smoking and drinking. EC was associated positively with smoking and alcohol drinking, with SB-adjusted OR of 1.73 (95% CI: 1.62-1.85) and 1.37 (95% CI: 1.28-1.46) in dose-response effects of increased intensity and longer duration of smoking/drinking. Moreover, garlic intake interacts with smoking [synergy index (S)=0.83, 95% CI: 0.67-1.02; ratio of OR=0.88, 95% CI: 0.80-0.98] and alcohol drinking (S=0.73, 95% CI: 0.57-0.93; ratio of OR=0.86, 95% CI: 0.77-0.95) both multiplicatively and additively. Our findings suggested that high intake of raw garlic may reduce EC risk and may interact with tobacco smoking and alcohol consumption, which might shed a light on the development of EC as well as a potential dietary intervention among high-risk smokers and drinkers for EC prevention in the Chinese population.

The effect of complete caloric intake restriction on human body odour quality

Previous studies on various vertebrates have shown that quantity and quality of food intake affect odour attractiveness as perceived by potential mates. In humans, the quality of body odour is similarly affected by ingested foods, such as by variation in meat and garlic intake. Nevertheless, it is not known whether quantity of food has an impact on human body odour attractiveness. Thus, here we tested how 48 h of complete caloric intake restriction affects the hedonic quality of human axillary odour.Odour samples (cotton pads fixed in both armpits and worn for 12 h) were obtained from healthy female donors across three conditions: i) during their habitual food regime; ii) after 48 h of complete caloric intake restriction (drinking water was provided), and iii) 72 h after restoration of caloric intake. Axillary samples were assessed by male raters regarding their pleasantness, attractiveness, femininity, and intensity. We also collected blood samples to assess physiological changes due to dietary restriction (e.g., glucose, sodium, albumin, and triacylglyceride assays) and anthropometric measurements at the same intervals as body odour samples.We found no differences in pleasantness, attractiveness and intensity between the odour samples collected at baseline and during complete caloric intake restriction. Interestingly, we found that body odours were rated more pleasant, more attractive and less intense after restoration of food intake as compared to the baseline and during caloric restriction. Our results suggest that restoration of food intake positively influences hedonic quality of human body odour which might thus provide cues to current fitness status and metabolic efficiency.

Garlic Supplementation Modified Enzymatic Omega‐6 Polyunsaturated Fatty Acid Oxidation in Mild Hypercholesterolemia

Dietary garlic has been shown to alleviate hypercholesterolemia, a condition associated with the development of cardiovascular disease. Reactive oxygen species take part in the disease progression, but it is unknown if antioxidant rich garlic arrests lipid and cholesterol oxidation in hypercholesterolemia. This study provides fermented garlic or non‐fermented garlic to mild hypercholesterolemia (total cholesterol: 5.2–6.2 mmol L−1) and determines its ability to relieve in vivo oxidative stress by measuring multiple oxidized lipid products of polyunsaturated fatty acid (PUFA) and cholesterol oxidation products (COPs) in plasma. Plasma fatty acids levels are also analyzed. After 13 weeks supplementation, both groups show a significant increase in α‐linolenic acid level (p < 0.05). Levels of arachidic acid increase and palmitoleic acid decreases in the group supplemented with non‐fermented garlic. Of the oxidized PUFA products, notably those derived from enzymatic oxidation of arachidonic acid, namely hydroxyeicosatetraenoic acid (HETE), show a significant difference. Levels of lipoxygenase mediate 5‐HETE and 12‐HETE, and CYP‐P450 mediates 9‐HETE and 11‐HETE decreases after non‐fermented garlic supplementation only (p < 0.05). Non‐enzymatic PUFA oxidation and COPs are not altered by garlic supplementation. Overall, only non‐fermented garlic intake shows selective antioxidant properties in mild hypercholesterolemia where limited effect is found in reducing lipid oxidation.Practical Applications: Current research provides a new insight for the use of garlic extract as a nutraceutical to reduce in vivo oxidative stress. The modified enzymatic oxidation of arachidonic acid in mild hypercholesterolemia after non‐fermented garlic extract intake potentially preventes the progression of chronic inflammation that can lead to complicated pathologies such as arthritis, cardiovascular diseases, and non‐alcoholic fatty liver disease.Garlic is a claimed functional food. The fermented form is proposed to have stronger antioxidant properties. Analysis of mild hypercholesterolemia plasma before and after fermented or non‐fermented garlic extract intake for 13 weeks revealed augmented α‐linolenic acid. Garlic appeared to be selective in the antioxidant property. Pro‐inflammatory lipid mediators (5‐, 9‐, 11‐, and 12‐HETE) released via enzymatic polyunsaturated fatty acid (PUFA) oxidation reduced after non‐fermented garlic extract intake only. However, intake of both garlic types did not reduce non‐enzymatic PUFA oxidation status.

Allium vegetables are associated with reduced risk of colorectal cancer: A hospital-based matched case-control study in China.

The present study aimed to investigate and identify the association between the intake of allium vegetables and colorectal cancer (CRC) in population. A hospital-based matched case-control study was conducted between June 2009 and November 2011 in three hospitals. Eight hundred thirty three consecutively recruited cases of CRC were frequency matched to 833 controls by age (within 2.5 years of difference), sex, and residence area (rural/urban). Demographic and dietary information were collected via face-to-face interviews using a validated food frequency questionnaire. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated by using unconditional logistic regression. A decreased CRC risk was observed for the consumption of total (aORs of high total allium intake compared with low total allium intake=0.21, 95% CI=0.14-0.30, P trend <0.001) and several individual allium vegetables including garlic, garlic stalks, leek, onion, and spring onion (P trend <0.05). By further sex-stratified analysis, allium vegetable intake was demonstrated to be inversely associated with the risk of CRC in both men and women. However, the association of garlic intake with cancer risk was not significant among those with distal colon cancer (aOR=0.53, 95% CI=0.27-1.05, P trend=0.248). In this analysis in a Northeast Chinese population, both men and women that the consumption of allium vegetables is associated with a reduced risk of CRC, regardless of colonic tumor subsite, with the exception of garlic intake in distal colon cancer.

Effect of garlic supplementation on serum C-reactive protein level: A systematic review and meta-analysis of randomized controlled trials.

The present study was designed to systematically review randomized controlled trials (RCTs) that report on the effects of garlic supplementation on serum C-reactive protein (CRP) levels. We conducted a literature search of Scopus, PubMed, Cochrane Library, and Google Scholar up to January 2018. Weighted mean differences (WMD) were estimated for net change in serum CRP. Subgroup analyses were also performed by duration of study, dose of supplementation, baseline CRP level, and the quality of studies. From 438 articles found and screened in our initial search, nine RCTs with the sum of total sample size of 363 were included in the meta-analysis. Compared with the controls, garlic intake significantly reduced the concentrations of serum CRP by 0.8mg/L (95% CI [-1.5, -0.1], p=0.02) with the evidence of heterogeneity among studies. Subgroup analyses showed that garlic significantly lowered CRP by 0.82mg/L (95% CI [-1.02, -0.62], p<0.001) among studies with a daily garlic dose ≥1,200mg/day and by 2.44mg/L (95% CI [-4.02, -0.87], p=0.002) among studies with baseline CRP ≥2mg/L. Current data confirmed that garlic supplementation would reduce serum CRP levels. However, the changes were related to the supplemental doses and baseline levels of serum CRP.

Quantification of volatile metabolites derived from garlic in human breast milk

Maternal garlic intake during pregnancy and the breastfeeding period has been reported to be associated with the potential of modulating later garlic acceptance in infants. However, the metabolism of garlic constituents in humans and their elimination and potential excretion into human milk are not yet fully understood. In previous studies, we identified volatile garlic-derived metabolites in human milk as well as in human urine, namely allyl methyl sulfide, allyl methyl sulfoxide and allyl methyl sulfone. To monitor the excretion of these garlic metabolites in a larger cohort, we quantified these metabolites in a total of 18 human milk sets, whereby each set comprised of one sample collected before and three samples after garlic consumption. The analyses revealed that the concentrations of the metabolites were most abundant 1–3.5 h after garlic consumption, with distinct differences between test persons regarding metabolite concentrations as well as temporal excretion.

The association of garlic with Helicobacter pylori infection and gastric cancer risk: A systematic review and meta-analysis.

Garlic may be protective against Helicobacter pylori infection and gastric cancer development. We conducted this study to quantitatively update evidence on garlic intake and gastric cancer with the inclusion of most recent cohort studies and qualitatively summarize epidemiological studies of garlic consumption and Helicobacter pylori infection. PubMed, Embase, MEDLINE, and Cochrane Library were searched on April 2018. We conducted a meta-analysis to determine whether garlic intake reduced gastric cancer risk using random-effect models and a systematic review to summarize evidence on the association between garlic consumption and Helicobacter pylori infection. Risk of bias was assessed using tools of Cochrane risk of bias and Robins-I for randomized and nonrandomized studies, respectively. Meta-analysis of 18 studies (142921 subjects) demonstrated high garlic consumption (as comparing the highest category to the lowest) was associated with a reduced gastric cancer risk (OR=0.51, 95% CI=0.44-0.57). This association became nonsignificant if only derived from the prospective studies (OR=0.95, 95% CI=0.66-1.24). Thirteen studies (4889 participants) were included in the systematic review for garlic consumption and Helicobacter pylori infection; ten of which found no significant results. The majority of these studies were poor in quality given the small sample size and high risk of bias. Pooled evidence, mainly from case-control studies, suggested a significant inverse association of garlic intake with gastric cancer risk. Given the limitations of included studies, current epidemiological evidence is not sufficient to reach any definite conclusion regarding the association of garlic with Helicobacter pylori infection.

Garlic intake and gastric cancer risk: Results from two large prospective US cohort studies.

Although many case-control studies suggested that garlic intake may reduce gastric cancer risk, evidence from prospective cohort studies has been lacking. We examined the association between garlic intake and subsequent risk of gastric cancer among 77,086 women in the Nurses' Health Study (1984-2014) and 46,398 men in the Health Professionals Follow-Up Study (1986-2014). Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models. We additionally examined garlic intake in relation to Helicobacter pylori (H. pylori) infection among 613 participants using logistic regression. During up to 30 years of follow-up, 292 participants were diagnosed with gastric cancer. The pooled multivariable RR of gastric cancer among participants who ate garlic, as compared to those who did not, were 1.11 (95% CI = 0.81-1.51) for the intake of garlic less than once per week, 0.98 (95% CI = 0.71-1.36) for one to four times per week and 1.39 (95% CI = 0.89-2.17) for five or more times per week (p for trend = 0.23). Similarly, no statistically significant association was observed cross-sectionally between garlic intake and H. pylori infection (comparing five or more times per week to never, pooled multivariable odds ratio = 1.66, 95% CI = 0.89-3.09; p for trend = 0.11). The findings from this large prospective study do not support the hypothesis that high garlic intake reduces risk of gastric cancer.

Bioaccessibility and permeability of bioactive compounds in raw and cooked garlic

Numerous studies have shown that organosulfur compounds (OSCs) from raw and cooked garlic act as bioactive phytochemicals. Nevertheless, data related to OSCs bioaccessibility is scarce. This information would be useful to establish how garlic should be consumed for maximize its beneficial effects. In the present work, cooking influence on OSCs bioaccessibility, intestinal permeability and blood stability was assayed. Target analytes were allicin, (E)/(Z)-ajoene, 2-vinyl-4H-1,3-dithiin (2-VD), diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS). The results showed that all OSCs studied were bioaccessible in raw and cooked garlic. In contrast, allicin, DAS and 2VD would be able to permeate less than 5% through the intestine. Furthermore, OSCs reacted rapidly with blood; less than 20% of 2VD, DAS and DADS could remain unreacted at the half hour. In conclusion, raw and cooked garlic intake provides bioactive OSCs that could be absorbed at a moderate rate. Raw garlic digestion showed a greater OSCs quantitative yield. 2-Vinyldithiin was the garlic compound that showed better permeability and stability.

The effect of garlic intake on glycemic control in humans: a systematic review and meta-analysis

Objective: To conduct a systematic review and meta-analysis of the effects of garlic intake on glycemic control in humans. Methods: We searched MEDLINE, EMBASE, EBSCO, and Science Direct as international data bases, and IranMedex, Magiran, and SID as local databases for studies on effect of garlic intake on glycemic control in humans published until March 2015. Our search included MeSH and non-MeSH terms.The quality of included studies was assessed using the Jadad scale. Results: Ten articles were eligible for current meta-analysis. The results showed that garlic intake could decrease fasting blood sugar (FBS) (P<0.001). To overcome the heterogeneity, studies were categorized into five subgroups. Accordingly, consumption of garlic as a food decreased FBS in comparison with garlic supplements (P=0.01). In addition, in comparison with healthy, diabetic, and hypercholesterolemic participants, garlic intake significantly reduced FBS in diabetic patients with hypercholesterolemia (P=0.001), and studies which had dependent design (cross-over or before-after) showed that garlic intake could decrease FBS (P<0.001). We could not observe any significant result through different subgroups of duration of intervention. Moreover, the results showed that garlic intake could decrease post prandial blood glucose (PPBG) (P=0.031), but could not significantly decrease Hemoglobin A1C (HbA1C) (P=0.1). Conclusion: The current analysis revealed that consumption of garlic as a food could significantly decrease FBS especially in patients suffering from both diabetes and hypercholesterolemia. However, it is suggested that garlic intake regardless of its source (food or supplement) might improve PPBG levels in humans.

A Review: Anti-microbial, Anti-inflammatory effect and Cardiovascular effects of Garlic: Allium sativum

Allium sativum is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and Allium chinense. With a history of several thousand years of human consumption and use, garlic is native to the region between the Mediterranean and China, and has long been a common seasoning worldwide. Herbs such as garlic with the potential to significantly modulate the activity of drug-metabolizing enzymes (notably cytochrome p450 isozymes) and/or the drug transporter P-glycoprotein participate in potential pharmacokinetic interactions with anticancer drugs. Among the active compounds present in the plant, DTS and DDS are the most active against yeasts and ajoene is the main compound responsible for the antiviral activity of garlic. A great deal of low quality clinical research has been conducted to determine the effect of garlic on preventing cardiovascular diseases and on various biomarkers of cardiovascular health, but as of 2015, the results were contradictory and it was not known if there are any effects. Because garlic might reduce platelet aggregation, people taking anticoagulant medication are cautioned about consuming garlic. Meta-analysis found decreased rates of gastric cancer associated with garlic intake, but cited confounding factors as limitations for interpreting these studies. Further meta-analyses found similar results on the incidence of gastric cancer by consuming allium vegetables including garlic. Garlic is known to cause bad breath (halitosis) and body odor, described as a pungent garlicky smell to sweat. This is caused by allyl methyl sulfide (AMS).

Aged Garlic Supplement Protects Against Lipid Peroxidation in Hypercholesterolemic Individuals.

The health benefits of raw garlic intake has been extensively studied, but little is known about the biological effects of aged garlic consumption. A randomized, placebo-controlled, parallel-arm, double-blinded trial involving 41 hypercholesterolemic individuals was conducted to simultaneously examine and compare the blood lipid lowering and antioxidant effects after acute and extended exposures to aged and raw garlic supplements (1080 mg daily). Aged and raw garlic did not affect blood lipid concentrations in these hypercholesterolemic participants after acute and 13-week supplementation. The plasma and urinary F2-isoprostanes concentrations were significantly decreased after 13 weeks of aged garlic treatment. Aged garlic supplementation over 13 weeks also significantly decreased serum lipid hydroperoxide concentration and myeloperoxidase activity. Raw garlic treatments did not affect the F2-isoprostanes concentrations in blood plasma and urine, and lipid hydroperoxides in blood sera. Acute effects on the measured parameters were absent for both garlic treatments. In separate in vitro experiments, aqueous methanolic extract of aged garlic inhibited F2-isoprostanes formation and myeloperoxidase activity in freshly isolated human neutrophils to a greater extent than the raw garlic extract and S-allylcysteine at equivalent dosing concentrations. The aged garlic preparation was found to contain significantly higher total phenolic and S-allylcysteine contents than the raw garlic precursor. Our data showed that supplementation with aged garlic, not its raw garlic precursor, reduced oxidative stress and alleviated lipid peroxidation, possibly via the inhibition of myeloperoxidase. The differential antioxidant actions of the aged and raw garlic may be related to their different total phenolic contents and, to a lesser extent, their S-allylcysteine contents.

Raw Garlic Consumption and Lung Cancer in a Chinese Population.

Evidence of anticancer properties of garlic for different cancer sites has been reported previously in in vitro and in vivo experimental studies but there is limited epidemiologic evidence on the association between garlic and lung cancer. We examined the association between raw garlic consumption and lung cancer in a case-control study conducted between 2005 and 2007 in Taiyuan, China. Epidemiologic data was collected by face-to-face interviews from 399 incident lung cancer cases and 466 healthy controls. We used unconditional logistic regression models to estimate crude and adjusted ORs (aOR) and their 95% confidence intervals (CI). Adjusted models controlled for age, sex, average annual household income 10 years ago, smoking, and indoor air pollution. Compared with no intake, raw garlic intake was associated with lower risk of development of lung cancer with a dose-response pattern (aOR for <2 times/week = 0.56; 95% CI, 0.39-0.81 and aOR for ≥2 times/week = 0.50; 95% CI, 0.34-0.74; Ptrend = 0.0002). Exploratory analysis showed an additive interaction of raw garlic consumption with indoor air pollution and with any supplement use in association with lung cancer. The results of the current study suggest that raw garlic consumption is associated with reduced risk of lung cancer in a Chinese population. This study contributes to the limited research in human population on the association between garlic and lung cancer and advocates further investigation into the use of garlic in chemoprevention of lung cancer. Cancer Epidemiol Biomarkers Prev; 25(4); 624-33. ©2016 AACR.

Garlic Influences Gene Expression In Vivo and In Vitro

There is a large body of preclinical research aimed at understanding the roles of garlic and garlic-derived preparations in the promotion of human health. Most of this research has targeted the possible functions of garlic in maintaining cardiovascular health and in preventing and treating cancer. A wide range of outcome variables has been used to investigate the bioactivity of garlic, ranging from direct measures of health status such as cholesterol concentrations, blood pressure, and changes in tumor size and number, to molecular and biochemical measures such as mRNA gene expression, protein concentration, enzyme activity, and histone acetylation status. Determination of how garlic influences mRNA gene expression has proven to be a valuable approach to elucidating the mechanisms of garlic bioactivity. Preclinical studies investigating the health benefits of garlic far outnumber human studies and have made frequent use of mRNA gene expression measurement. There is an immediate need to understand mRNA gene expression in humans as well. Although safety and ethical constraints limit the types of available human tissue, peripheral whole blood is readily accessible, and measuring mRNA gene expression in whole blood may provide a unique window to understanding how garlic intake affects human health.

An umbrella review of garlic intake and risk of cardiovascular disease

PurposeTo gain further insight into the strength of evidence and extent of possible biases in the scope of studies investigating the impact of garlic and garlic supplement intake on biomarkers of cardiovascular disease, we performed an umbrella review of all published meta-analyses synthesizing data from both observational studies and randomized controlled trials. MethodsElectronic database PubMed (between 1966 and June 2015) was searched for systematic reviews and meta-analyses using following search terms: (“garlic” OR “allium sativum” OR “allicin” OR “organosulfur”) AND (“cardiovascular” OR “coronary” OR “cholesterol” OR “triglyceride” OR “atherosclerosis” OR “blood pressure” OR “hypertension” OR “blood glucose”) AND (“systematic review” OR “meta-analysis”), with no restriction to calendar data and language. Hand-search of reference lists and relevant clinical guidelines was performed as well. ResultsNine systematic reviews investigated the effects of garlic on lipid parameters and eight systematic reviews analyzed the effects on blood pressure parameters were identified. Eight of nine meta-analyses synthesizing the effect of garlic on blood lipids reported significantly decreased total cholesterol levels. Inconsistent results could be detected for HDL-cholestrol, LDL-cholesterol, and triacylglycerols. The effect of garlic on systolic blood pressure showed consistent results across publications with 7 out of 8 meta-analyses demonstrating a substantial decrease in systolic blood pressure. Similar results could be reported regarding the effect of garlic on diastolic blood pressure, i.e. 6 out of 8 meta-analyses detected significant reductions in diastolic blood pressure levels following interventions with garlic. ConclusionAccording to the data summarized in the present umbrella review, garlic preparations as well as garlic exerted some positive effects on indicators and biomarkers of cardiovascular disease, typically without causing any serious side effects. However, with regard to the substantial heterogeneities between the different trials enrolled in the various meta-analyses of this review, a conservative interpretation of the outcome seems to be appropriate.

Allium vegetables and upper aerodigestive tract cancers: a meta-analysis of observational studies.

To provide updated quantitative overall estimations of the relation between total allium, garlic, and onion intake on the risk of cancer of the upper aerodigestive tract (UADT). We combined data of published observational studies (21 case-control and four cohort studies), using a meta-analytic approach and random effects models. The overall relative risks (RR) and 95% confidence intervals (CIs) for the squamous cell carcinoma of the UADT were 0.79 (95% CI 0.56-1.11) for total allium, 0.74 (95% CI 0.57-0.95) for garlic, and 0.72 (95% CI 0.57-0.91) for onion for the highest versus the lowest consumption. The inverse relation was apparently stronger in case-control studies (RR 0.56, 95% CI 0.38-0.83 for total allium), in Chinese studies (RR 0.67, 95% CI 0.45-0.98 for garlic intake), and for esophageal than for head and neck cancers. Apparently, there was no relation between allium vegetable intake and adenocarcinoma of the esophagus. We found a moderate inverse association between allium vegetable intake and the risk of squamous cell carcinoma of the UADT in case-control studies. The relation was unclear in cohort studies and for adenocarcinoma of the esophagus.