garlic

Authors:

Paola Tedeschi

Findings:

This review summarizes evidence on the therapeutic potential of allicin and Aged Garlic Extract (AGE) for Alzheimer's Disease, highlighting their potent anti-inflammatory, antioxidant, and neuroprotective activities observed in experimental models. The paper discusses their chemical composition, metabolism, bioavailability, and signaling mechanisms, particularly focusing on how allicin and AGE can improve learning and memory.

Participants:

Review of studies using various experimental models, primarily animal models (mice including APP/PS1 double transgenic, C57BL/6, Senescence-Accelerated Mice (SAM), APP-Tg, Tg2576, D-galactose-treated, streptozotocin-induced, Aβ-induced, scopolamine-treated; rats including those with traumatic spinal cord injury, Aβ-induced, LPS-treated) and in vitro cell models (neuronal PC12 cells, undifferentiated PC12 cells, hippocampal slice cultures, rat hippocampal neurons).

Dosage:

The review details various dosages from the summarized experimental studies. For allicin, examples include 10 mg/kg/day via intragastric administration, 180 mg/kg/day in diet, or 2-50 mg/kg via intraperitoneal injection in animal models. For Aged Garlic Extract (AGE) or its components like S-allyl cysteine (SAC), examples include 2% (w/w) AGE in diet, 0.01%-1.0% AGE in cell media/diet, 25-500 mg/kg AGE p.o., 1-100 µM SAC in vitro, or 20-100 mg/kg SAC in animal models, with varying administration routes and durations.

Study Quality Assessment:

This document is a review article summarizing findings from multiple experimental (in vitro cell culture and in vivo animal model) studies. The review itself notes that the summarized studies are derived from cellular or mouse models and that clinical trials concerning these compounds and Alzheimer's Disease are not present, suggesting this evidence needs confirmation in human studies.

All Effects:

Authors:

Muhammad Shahid Nadeem

Findings:

This review describes allicin as an antioxidant and neuroprotective agent that ameliorates cognitive impairment in neurodegenerative and neuropsychological disorders. Allicin achieves this by reducing reactive oxygen species (ROS) through NOX enzyme downregulation and promoting antioxidant enzymes, inhibiting neuroinflammation (via TLR4/MyD88/NF-κB, P38, JNK pathways), inhibiting cholinesterases (relevant to Alzheimer's disease), helping balance neurotransmitters (relevant to ASD and ADHD), and protecting neurons in spinal cord injury by promoting Nrf2. The review concludes that while allicin shows promise, further clinical studies are required to establish its therapeutic efficacy.

Participants:

Review of studies. Participants in the reviewed preclinical studies include animal models (Wistar rats, rabbits, mice including Nrf2 knockout and APP/PS1 models) and human cell lines (HUVECs, RPEs, Caco-2, U87-MG cells). Reviewed clinical studies involved newborn infants with thrush, 20 patients with Behcet's disease, 96 patients in a trial for aphthous ulceration, 52 Chinese patients with oral submucous fibrosis, and participants in an ongoing cancer trial and a trial for common cold.

Dosage:

The reviewed literature mentions a low concentration of allicin (0.4 mM) inhibiting platelet aggregation. Allicin's inhibition of telomerase is described as dose-dependent. Specific dosages for neuroprotection or cognitive improvement are not detailed in this review, and the review notes that dose optimization studies are required.

Study Quality Assessment:

The text is a review article. For the studies it reviews, it mentions: primarily preclinical studies (animal models, human cell lines); a few clinical studies including a 'small-scale clinical study involving only 20 patients', a 'randomized double blind placebo trial involving 96 patients', and an ongoing clinical trial from clinicaltrials.gov with 'no results have been yet reported'. The review acknowledges a limitation: 'Human trials and dose optimization studies are required for the establishment of allicin as a neuroprotective agent'.

All Effects:

Authors:

Ao Shang

Findings:

Garlic contains diverse bioactive compounds (e.g., allicin, alliin, S-allyl-cysteine) and studies show its constituents exhibit antioxidant, anti-inflammatory, antibacterial, antifungal, immunomodulatory, cardiovascular protective, anticancer, hepatoprotective, digestive system protective, anti-diabetic, anti-obesity, neuroprotective, and renal protective properties. Garlic is a natural source of bioactive sulfur-containing compounds with applications in functional foods or nutraceuticals for disease prevention and management.

Study Quality Assessment:

Review article. Conflict of interest statement: The authors declare no conflict of interest.

All Effects:

Authors:

Ligia J Dominguez, Mario Barbagallo

Findings:

Effective pharmaceutical treatments for age-related cognitive decline are lacking, emphasizing the importance of prevention strategies. There is extensive evidence supporting a relationship between diet and cognitive functions, suggesting nutritional approaches to prevent or slow cognitive decline could have a remarkable public health impact.

All Effects:

Authors:

BC Mathew, RS Biju

Findings:

This review suggests garlic possesses neuroprotective effects primarily through its interrelated anti-atherogenic, antioxidant, and anti-apoptotic properties. These actions may help reduce the risk of dementia, including Alzheimer's disease and vascular dementia, by mitigating cardiovascular risk factors (like high cholesterol, LDL oxidation, platelet aggregation, hypertension, homocysteinemia) and by protecting neuronal cells against beta-amyloid toxicity, oxidative stress, and apoptosis. Different garlic preparations (e.g., raw garlic, Aged Garlic Extract (AGE), garlic oil, garlic powder) and their bioactive constituents (e.g., S-allyl-cysteine (SAC), allicin, diallyl disulfide (DADS)) are discussed for these beneficial effects.

Participants:

The review covers studies involving human participants (hypercholesterolemic, healthy, atherosclerotic, hypertensive, smoking & non-smoking individuals) and various animal models (rats, rabbits, chickens, swine, mice, Sprague Dawley rats, Wistar rats, Alzheimer's transgenic mice). It also discusses in vitro research using diverse cell lines (e.g., PC12 neuronal cells, human T cells, vero kidney cells, human FL amniotic cells) and tissue preparations (e.g., rat hepatocytes, rat liver microsomes).

Dosage:

The review mentions various dosages across different studies and contexts: In animal studies (mostly rats): raw garlic juice at 5 ml/kg (resulted in death); chronic administration of garlic powder at 50 mg/day (inhibited spermatogenesis); garlic extract at 100–120 mg protein/kg body weight (intraperitoneally injected); diallyl trisulfide (DAT) rich garlic oil supplement at 5 or 50 mg/kg body weight (fed); oral administration of diallyltetrasulfide (DTS) at 40 mg/kg/day; Aged Garlic Extract (AGE) at 500 mg/ml/kg body weight (i.p.). In humans: ingestion of one or two cloves of garlic per day is considered safe; populations consuming ≥300 mg of garlic powder/day for ≥2 years showed attenuation of age-related aortic stiffness. In vitro studies: DTS at 5–50 µg/ml. It is suggested to stop high doses of garlic seven to ten days before surgery.

Study Quality Assessment:

The review analyzes studies with designs including Randomized Controlled Trials (RCTs), double-blind placebo-controlled, and non-placebo-controlled studies. It notes specific sample sizes (e.g., N=11, N=23, N=34, N=46, N=75 in summarized clinical trials) and trial durations (e.g., 14 days, 2 months, 12 weeks, 4 months, 5 months, 6 months, 'at least four weeks'). Numerous specific biochemical and physiological measurement methods are described (e.g., assays for enzyme activities like HMG-CoA reductase, G6PD; LDL oxidation measurement; platelet aggregation tests; histopathology; chromatographic methods; triphenyltetrazolium staining; flow cytometric assessment). Limitations acknowledged include 'inadequate randomization, selection of inappropriate subjects, and the short duration of trials' potentially accounting for inconsistent findings, the stated need for 'further well-designed randomized, larger clinical trials of longer duration using well standardized preparations', and observations that the 'antioxidant effect of garlic in humans is not well studied' and 'antihypertensive effects of garlic...remain controversial'.

All Effects: