Contents
What it is
Garlic is the bulb of a plant in the onion genus, a relative of onion, leek and chive, native to Central Asia. A head splits into cloves, and each clove is a single bud. An intact clove smells of almost nothing; the moment it is cut or crushed the cells rupture and an enzyme converts alliin into allicin, which is where the characteristic aroma and bite come from. That is why a whole roasted head and a finely minced clove taste like two different ingredients.
Scientific name Allium sativum
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
- Moderate evidence
It lowers blood pressure, modestly
A meta-analysis of 20 randomised trials (970 participants) found systolic pressure down 5.1 mmHg and diastolic down 2.5 mmHg on average. Looking only at those who started above 140/90, systolic fell 8.7 mmHg. It is no replacement for medication, but as one lever among several in a diet, the number is meaningful.[1]
- Moderate evidence
It nudges total and LDL cholesterol down
A review of 39 randomised trials (2,300 adults) found total and LDL cholesterol about 10% lower when garlic was taken for more than two months. There is a condition attached, though: this came from people whose total cholesterol was slightly elevated, just over 200 mg/dL. It is not a basis for expecting the same drop if your numbers are already normal.[1]
- Early research
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.[2]
- Moderate evidence
It is antioxidant and antimicrobial
The two effects rest on different evidence. The antioxidant side has human trials: a meta-analysis of 7 randomised trials (317 people) found higher total antioxidant capacity and lower lipid peroxidation (MDA). The antibacterial and antifungal activity, by contrast, is still lab-stage. That is a long way from treating an infection with garlic.[3][4]
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 3–6 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 — have it with a meal.
- For the breath: milk, apple, green tea and raw parsley have actually been measured to help.
How to read the grades
Each benefit carries a label showing how far research on people supports it. Grades differ between items even within the same ingredient.
- Nutrition data
- A fact verifiable from food composition databases or health authorities. This is a different kind of statement from a clinical effect.
- Strong evidence
- Consistently confirmed across randomised controlled trials or meta-analyses.
- Moderate evidence
- Human studies exist, but effect sizes are small or results are mixed.
- Early research
- Cell or animal work, or small preliminary studies.
- Not established
- Commonly claimed, but not confirmed in studies on people.
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 7–10 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 kcal7%
- Carbohydrates
- 33.1 g12%
- Fiber
- 2.1 g8%
- Protein
- 6.4 g13%
- Fat
- 0.5 g<1%
- Vitamin C
- 31 mg34%
- Vitamin B6
- 1.24 mg73%
- Manganese
- 1.67 mg73%
- Selenium
- 14 µg25%
Percentages are of the US FDA Daily Value for adults and children 4 and over. National reference intakes differ by sex and age.
Calculate this alongside other ingredients →
Key nutrients
By health concern
Dishes with this ingredient
- Korean spinach namul10 min
- Broccoli stir-fried with garlic15 min
- Oven-baked salmon with garlic25 min
- Korean beef and sea mustard soup35 min
- Lentil and tomato soup35 min
- Chicken and chilli stir-fry20 min
- Broccoli and sunflower seed salad15 min
- Sardine and tomato toast10 min
- Baked trout with broccoli25 min
- Herring braised in tomato30 min
- Barley and mushroom risotto45 min
- Chickpea and kale stew30 min
- Anchovy and peanut stir-fry15 min
- Shrimp and broccoli stir-fry20 min
- Bell pepper and tofu stir-fry20 min
- Squid and bell pepper stir-fry20 min
- Corn sautéed with garlic butter20 min
- Clear kelp and tofu soup20 min
- Asparagus and prawn stir-fry15 min
- Clam and buckwheat noodles30 min
- Lamb and vegetable skewers30 min
- Turkey and pepper stir-fry20 min
- Pineapple and pork skewers45 min
- Mussels in tomato25 min
- Roast Brussels sprouts with walnuts30 min
- Mushrooms sautéed with garlic15 min
- Beef and radish soup40 min
- Octopus and potato salad60 min
- Mint yoghurt sauce10 min
- Cashew chicken stir-fry25 min
- Steamed eggplant with garlic dressing20 min
- Soybean sprout soup20 min
- Lettuce sesame salad10 min
- Macadamia and spinach pesto15 min
- Celery and shrimp stir-fry15 min
- Cheonggukjang stew25 min
- Oyster mushrooms stir-fried with sesame oil15 min
- Green pea and mint soup20 min
- Roasted Jerusalem artichokes35 min
- Clear cod and radish soup30 min
Compare with
Sources
The databases and health authorities this article's nutrition figures and health statements draw on.
- 1Garlic Lowers Blood Pressure in Hypertensive Individuals, Regulates Serum Cholesterol, and Stimulates Immunity: An Updated Meta-analysis and ReviewMeta-analysisRied K J Nutr 2016PMID 26764326
- 2Garlic for the common coldSystematic reviewsLissiman E, et al. Cochrane Database Syst Rev 2014PMID 25386977
- 3An overview of the antifungal properties of allicin and its breakdown products--the possibility of a safe and effective antifungal prophylacticResearch literatureDavis SR Mycoses 2005PMID 15743425
- 4The effects of garlic supplementation on oxidative stress markers: A systematic review and meta-analysis of randomized controlled trialsMeta-analysisMoosavian SP, et al. Complement Ther Med 2020PMID 32444050
- 5USDA FoodData CentralFood composition database
- 6NIH Office of Dietary SupplementsHealth authority
- 7Cochrane LibrarySystematic reviews
- 8PubMedResearch literature
