What is allicin?
Allicin is an organic sulfur compound that belongs to indoles; it naturally occurs in crushed garlic (Allium sativum) .
Foods High in Allicin
Allicin-rich foods include garlic, onions, shallots, Chinese chives and leeks .
Garlic supplement that contain allicin or its derivatives :
- Fresh garlic cloves. Creation of allicin from alliin is stimulated by chopping raw garlic, and prevented by garlic cooking, since the enzyme that converts alliin to allicin is destroyed. To get an optimal amount of allicin, garlic should be either eaten raw, or chopped and kept ten minutes before cooking.
- Powdered or dehydrated garlic
- Steam distilled garlic oil
- Garlic oil macerate
Garlic Supplements Health Benefits
Garlic is PROBABLY EFFECTIVE in:
- High blood pressure.
- Fungal infections, such as ringworm, jock itch and athlete’s foot (when applied on the skin)
Garlic supplements are PROBABLY INEFFECTIVE  in the prevention or treatment of cancer (breast, colorectal, esophageal, gastric, lung, multiple myeloma, prostate), cystic fibrosis, diabetes mellitus type 2, high cholesterol, high blood pressure and stomach infections caused by a bacterium Helicobacter pylori and other infections, leg pain caused by poor blood circulation in the legs or as a mosquito or tic repellent.
There is INSUFFICIENT EVIDENCE  about the effectiveness of garlic supplements in the prevention or treatment of angina pectoris (heart related chest pain), atherosclerosis, benign prostatic hyperplasia, common cold, corns, fibrocystic breast disease, gastritis, hair loss heart disease, hepatitis, lead poisoning, muscle soreness after exercise, scleroderma, thrush (oral candidiasis) and warts, or in improving athletic performance.
Garlic Safety: Toxicity, Side Effects
Garlic is LIKELY SAFE when taken by mouth in appropriate amounts short-term . The toxicity and safety of a long-term use of garlic supplements has not been evaluated yet, though .
Side effects of garlic supplements may include unpleasant breath and body odor, heartburn, nausea, vomiting, bloating, diarrhea, increased risk of spontaneous or postoperative bleeding and allergic reactions .
Garlic supplements are POSSIBLY UNSAFE when taking by children or during pregnancy and breastfeeding . In one study, garlic odor of breast milk prolonged the attachment of babies to the breast .
Who may need to avoid garlic supplements?
Individuals with the following conditions may need to avoid garlic supplements :
Bleeding disorders. Garlic, especially fresh garlic, might increase the risk of bleeding in individuals with bleeding disorders or in those undergoing surgery.
Low blood pressure: Garlic can lower blood pressure. In theory, taking garlic might make blood pressure become too low in people with low blood pressure.
Garlic supplements may reduce the effectiveness of drugs, such as isoniazid, saquinavir anddrugs for HIV/AIDS (nevirapine, efavirenz), birth control pills, cyclosporine, enflurane, halotane, lovastatin or others .
Garlic does not seem to increase the effect of blood thinners .