Remedy · root & spice
Garlic: what the evidence says about blood pressure, cholesterol and colds
Garlic supplements have shown small drops in blood pressure in people with hypertension. The cholesterol and cold evidence is weaker, and supplements can interact with some drugs.
By the editors of Alimentotherapy Last reviewed 3 min read Not medical advice
Garlic
Allium sativum
Best-supported use: Blood pressure in people with hypertension
The short answer
In placebo-controlled trials, garlic supplements lowered systolic blood pressure by a few points on average, with larger drops in people who started with high blood pressure Ried 2016. NCCIH describes the effects on cholesterol and blood pressure as small, and garlic supplements can raise bleeding risk and sharply lower blood levels of the HIV drug saquinavir NCCIH; Piscitelli 2002.
The evidence, use by use
Each claim graded on human studies only. How we grade
| Use | Grade | What the research found |
|---|---|---|
| Blood pressure in people with high blood pressure | Moderate | A meta-analysis of 20 trials (970 people) found garlic preparations lowered systolic pressure by about 5 mm Hg versus placebo, and by about 8.7 mm Hg in trials of people with hypertension. Ried 2016 |
| Total cholesterol and triglycerides | Limited | Pooling 26 placebo-controlled trials, garlic lowered total cholesterol and triglycerides slightly but did not change LDL or HDL cholesterol. NCCIH calls the effect small. Zeng 2012; NCCIH |
| Fewer or shorter colds | Limited | Cochrane found only one eligible trial (146 people): those taking a daily garlic supplement for 12 weeks reported fewer colds, but recovery time was similar and the reviewers said little can be concluded. Lissiman 2014 |
Blood pressure
The trials mostly used garlic supplements such as aged garlic extract or dried garlic powder, taken daily for weeks to months. In the updated meta-analysis, systolic pressure fell by about 5 mm Hg and diastolic by about 2.5 mm Hg compared with placebo. In the subgroup of trials in people with hypertension, the drops were about 8.7 and 6.1 mm Hg Ried 2016. NCCIH is more cautious, describing the blood pressure evidence as limited and the effect as small NCCIH.
Garlic is not a replacement for prescribed blood pressure medicine. If your readings are high, the diet patterns with the most evidence are covered on heart health.
Cholesterol
Results on cholesterol have been inconsistent for decades. A 2012 meta-analysis of 26 trials found small reductions in total cholesterol and triglycerides, with larger effects in longer trials and in people with higher starting cholesterol, but no change in LDL or HDL cholesterol Zeng 2012.
Raw, cooked or capsules
Trials tested standardized supplements, so we cannot say how much fresh garlic matches a trial dose. Garlic in cooking is safe for nearly everyone and is part of many healthy cuisines.
Safety
Do not put raw crushed garlic on skin. NCCIH warns that fresh raw garlic used topically can cause severe skin irritation and chemical burns NCCIH.
Drug interactions
In a study of 10 healthy volunteers, three weeks of garlic caplets cut blood levels of the HIV protease inhibitor saquinavir by about half, and levels had not fully recovered 10 days after stoppingPiscitelli 2002. Garlic supplements may also add to the effect of anticoagulants and aspirin on bleeding NCCIH. See the interactions checker.
Before you try it: safety and interactions
Who should avoid it or ask first
- You take an anticoagulant or aspirin: ask your prescriber before garlic supplements.
- You have surgery coming up: tell your surgical team about garlic supplements.
- You take saquinavir or other HIV medicines: talk to your HIV clinician before any garlic supplement.
Possible side effects
- Breath and body odor, abdominal pain, flatulence and nausea.
- Allergic reactions in some people.
- Skin irritation and chemical burns if raw garlic is applied to the skin.
Pregnancy and breastfeeding
Garlic in food is fine. NCCIH says garlic in amounts greater than those found in food may not be safe in pregnancy or while breastfeeding. NCCIH; Piscitelli 2002
Medicine interactions
- Garlic supplements and saquinavir, an HIV protease inhibitorIn a controlled NIH study in 10 healthy volunteers, three weeks of garlic caplets cut saquinavir blood levels by about half, and levels had not fully recovered 10 days after stopping garlic.Established
- Garlic supplements and warfarin and other anticoagulants, aspirin and antiplatelet drugsGarlic supplements may increase the risk of bleeding, which matters when combined with drugs that also affect bleeding or before surgery. In a small trial, aged garlic extract did not increase bleeding in closely monitored warfarin patients.Probable
Check another food or medicine in the interactions list.
Common questions
How much does garlic lower blood pressure?
In a 2016 meta-analysis of 20 trials, garlic supplements lowered systolic blood pressure by about 5 mm Hg versus placebo, and by about 8.7 mm Hg in people who started with hypertension. It is not a substitute for prescribed medicine.
Does garlic help with colds?
The evidence is thin. A Cochrane review found only one eligible trial, in which people taking a daily garlic supplement reported fewer colds, but recovery time was similar and the reviewers said little can be concluded.
Can garlic supplements interact with medicines?
Yes. Garlic supplements may raise bleeding risk with anticoagulants and aspirin, and in a study of healthy volunteers they cut blood levels of the HIV drug saquinavir by about half. Ask your prescriber before taking them.
Sources
Primary research and government sources, each checked on the date this page was reviewed.
- PubMedRied K. Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol, and stimulates immunity: an updated meta-analysis and review. J Nutr. 2016. PMID 26764326.
- PubMedZeng T, et al. A meta-analysis of randomized, double-blind, placebo-controlled trials for the effects of garlic on serum lipid profiles. J Sci Food Agric. 2012. PMID 22234974.
- CochraneLissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database Syst Rev. 2014. PMID 25386977.
- PubMedPiscitelli SC, et al. The effect of garlic supplements on the pharmacokinetics of saquinavir. Clin Infect Dis. 2002. PMID 11740713.
- NCCIHNational Center for Complementary and Integrative Health. Garlic: Usefulness and Safety.
Keep reading
- GoalFood for a healthy heart: blood pressure and cholesterolEating patterns have the strongest heart evidence: DASH for blood pressure, Mediterranean for heart events, and soluble fiber from oats, barley or psyllium for cholesterol.
- RemedyBeetrootBeets are rich in dietary nitrate, which the body turns into nitric oxide. Short trials show a small drop in blood pressure measured at the clinic; longer, more careful measurements have not confirmed it.
- RemedyOily fishSalmon, sardines, mackerel and their kin are the main food source of the omega-3s EPA and DHA. The case for eating them is stronger than the case for fish oil capsules.
- ToolFood and drug interactionsCheck a remedy or food against common medicines.