Garlic (Allium Sativum): Benefits, Uses, Safety and Dosing

Garlic, also commonly known as kitungu saumu, stinking rose, or poor man’s treacle, is a common culinary spice found in most home kitchens. It belongs to the family Amaryllidaceae and is native to Central Asia and northeastern Iran. It is currently cultivated in China, India, Spain, parts of the United States (California), Egypt, and South Korea. It is found as either a hard neck or a soft neck.

Garlic can be used as follows:

• Reduce blood pressure and arterial stiffness
• Lower total bad cholesterol in the body
• Support the immune system
• Reduce fasting blood sugar
• Improve exercise tolerance
• Reduce toxin levels in blood (lead).

Medical uses and ethnopharmacological profile of Garlic

Traditional uses

It was given to athletes to improve stamina and also as a common battlefield wound antiseptic to prevent wound gangrene. It was also used as a vermifuge and a heart tonic for ‘vata’ disorders, and ‘da suan’ was used to eliminate food stagnation in the belly and counteract toxins. It was also used in pulmonary issues like regulating mucus secretions as an expectorant.

Clinical uses and Research

Anti-hypertension: In adults with hypertension, a 600-1200 dose of bulb extract elicited an average reduction of systolic and diastolic blood pressure. This was through the action of S-allyl cysteine that stimulated nitric oxide releases, thus having a vasodilatory effect.

Hyperlipidemia: In a clinical trial, standardized extract from bulb powder administered at doses of 600-900 mg once daily for 8-12 weeks was able to reduce cholesterol by 7-10%. This was through the action of alliin broken down to allicin that inhibited the enzyme HMG CoA responsible for the synthesis of cholesterol, hence reducing levels of synthesized cholesterol. ( Adler Aj 1997)

Immune support: In volunteers administered with 2.56 grams of bulb extract for 90 days, there was recorded a 61% reduction in the number of days with cold and flu symptoms like headache and runny nose. This was through the action of water-soluble polyphenols that increased the proliferation of natural killer cells in the body.

Oral and pancreatic precancerous lesions: In research with participants suffering from oral submucous fibrosis, topical/systemic allicin-rich extract at a dose of 900 mg daily showed improvement in flexibility of mouth opening, reduction in burning mouth sensations, and generally improved the quality of life. Allicin acted by decreasing levels of tumor necrosis factor alpha protein activity and also inhibiting collagen cross-linking.

Glycemic control: In patients with type 2 diabetes mellitus, garlic powder tablets (used as an adjunct to metformin) at a dose of 600-1500 mg daily for 12-24 weeks was able to significantly reduce fasting blood sugars and Hb1A c. Allicin and S-allyl cysteine acted by enhancing insulin secretion from pancreatic beta cells. It was also suspected to inhibit the glycation of proteins.

In Vivo uses and Research

Antitoxin: In rats with lead-induced toxicity, bulb aqueous extract at 100 mg/kg daily for 4 weeks was able to reduce levels of lead in tissues and blood. The sulfhydryl groups acted through chelation of heavy metals as well as reducing the oxidative stress on the liver and kidneys. ( Senapti 2001)

Atherosclerosis: Raw garlic bulb juice fed to diabetic rats at 250 mg/kg for 8 weeks elicited a decrease in serum glucose levels, triglycerides, and cholesterol. The compound S-methyl cysteine was thought to act via increasing both insulin secretion and sensitivity.

Type 2 diabetes: Bulb oil extract at 5 mg/kg thrice a week decreased atherosclerotic plaque area in the aorta. Diaryl trisulfide was isolated as the compound that inhibited lipid accumulation and vascular muscle cell proliferation.

In Vitro Uses and Research

Anti-tumor: The isolated colorectal cancer cell lining when exposed to bulb oil soluble extract showed a dose-dependent inhibition of cancer cell stability and proliferation. This was due to the action of ajoene and diallyl sulfide that induces programmed cell death through reactive oxygen species. (Zhou 2020)

Antibacterial: In methicillin-resistant Staphylococcus aureus, freshly crushed juice rich in allicin was able to inhibit bacterial activity. It acted via reacting with thiol groups of bacterial enzymes.

Neuroprotection: In hippocampal neurons of rats, bulb extract protects against amyloid beta-induced neurotoxicity. This was through the scavenging of superoxide radicals and inhibition of NF-kB activation by the compound S-allyl cysteine.

Safety And Dosing profile of Garlic

Forms and Dosing

Fresh garlic– 2-5 grams daily

Powdered garlic– 2-5 grams

Aged extract– 600-2400 mg a day

Garic oil – 2- 5 drops of highly concentrated oil.

Poultice – applied to skin

Standardized capsules and tablets– 600-1200 mg in divided doses.

• Hyperlipidemia-600-1200 mg a day
• Hypertension- 600-900mg a day
• Artherosclerosis- 1.2-2.4 grams a day
• Common cold- 180 mg a day

Interactions

• Antihypertensives (lisinopril, losartan, amlodipine)- may lead to risk of hypotension
• Blood thinners- may lead to risk of excessive bleeding
• Antiviral protease inhibitors, like saquinavir, reduce drug concentrations, hence efficiency.
• Antidiabetic- may be used as an adjunct, as it may cause hypoglycemia
• Immunosuppressants, like cyclosporine- may alter the bioavailability and effectiveness of the drug

Side effects

• Heartburn and acid reflux
• Abdominal cramping and pain
• Bad breath
• Bloating and flatulence
• Contact dermatitis
• Acantholysis (rare)

Contraindications

• Peptic ulcers and gastritis
• Irritable bowel syndrome
• Hypotension
• Long contact period for crushed garlic poultice or paste