Until you cut or crush it, allicin does not exist in garlic. Breaking the cells lets a compound called alliin meet an enzyme called alliinase, and the reaction that follows takes about ten minutes.
Most research on garlic's health effects targets allicin and the sulphur compounds it breaks down into. Which means how you handle garlic matters about as much as how much of it you eat.
Key benefits
- 1
It lowers blood pressure, modestly
Pooling randomised trials in people with hypertension, garlic supplementation reduced systolic pressure by roughly 5โ8 mmHg on average. In people with normal blood pressure, almost nothing changed. It is no replacement for medication, but as one lever among several in a diet, the number is meaningful.
- 2
It nudges total and LDL cholesterol down
Trials running eight weeks or longer report small reductions โ on the order of 5โ10% โ in total and LDL cholesterol. Triglycerides and HDL showed no consistent change.
- 3
It may reduce how often you catch a cold
In one twelve-week trial, the group taking a garlic supplement recorded fewer colds than the placebo group. The number of studies is small, so treat this as promising rather than settled.
- 4
It is antioxidant and antimicrobial
Allicin and related sulphur compounds show clear antibacterial and antifungal activity in the lab, and in the body they tend to raise antioxidant enzyme activity. That is a long way from treating an infection with garlic.
How to eat it well
- Crush it, then wait ten minutes before cooking. Heat applied immediately destroys alliinase, and no allicin forms.
- One or two raw cloves a day (about 3โ6 g) is plenty. Cooked garlic can be used more generously.
- If raw garlic is too harsh, black garlic or aged garlic extract are the forms most often used in blood pressure research.
- Eating raw garlic on an empty stomach irritates the gastric lining for many people โ have it with a meal.
- For the breath: milk, apple, green tea and raw parsley have actually been measured to help.
What to watch out for
- With gastritis or reflux, raw garlic can make symptoms worse.
- Combined with anticoagulants such as warfarin, it may increase bleeding tendency. High-dose supplements are usually stopped 7โ10 days before surgery.
- Garlic is high in FODMAPs, so it can trigger bloating and gas if you have irritable bowel syndrome.
- Contact dermatitis and allergic reactions occur, though rarely.
Nutrition
Approximate values per 100 g edible portion.
- Calories
- 149 kcal
- Carbohydrates
- 33.1 g
- Fiber
- 2.1 g
- Protein
- 6.4 g
- Fat
- 0.5 g
- Vitamin C
- 31 mg
- Vitamin B6
- 1.24 mg
- Manganese
- 1.67 mg
- Selenium
- 14 ยตg
Key nutrients
- Allicin
- Vitamin B6
- Manganese
- Selenium
- Vitamin C