Valued as a trusted remedy for millennia, we look at the evidence behind the health claims about garlic.
Aphrodisiac, currency, food, medicine, vampire repellent – garlic has had many uses throughout the ages.
Garlic contains vitamins C and B6, manganese, selenium and other antioxidants (notably allicin).
More recent evidence-based research suggests garlic may be effective against high blood pressure, cardiovascular disease, cholesterol, colds and some cancers.
We've teamed up with the British Dietetic Association (BDA) to see if the health claims about garlic stand up to closer scrutiny.
The evidence on garlic health claims
Does garlic lower high blood pressure?
An authoritative review from 2012 of the best available evidence on the use of garlic to treat high blood pressure identified one good-quality study that suggested 200mg of garlic powder three times daily reduced blood pressure. However, the review concluded there was insufficient evidence to say if garlic was an effective means for treating high blood pressure and reducing death rates.
Can garlic reduce cholesterol?
A well-conducted review from 2009 of 29 good-quality studies involving a combined total of 1,794 participants concluded that garlic – mainly garlic powder – produced "modest reductions" in total cholesterol levels.
Does garlic prevent the common cold?
A good-quality review from 2012 of the best available evidence concluded there was insufficient evidence regarding the effects of garlic supplements in treating or preventing colds. Most studies that claimed this were poor quality. The review said one reasonably good study suggested garlic may prevent colds, but more research was needed to back up the finding.
Will garlic protect against cancer?
The evidence is mixed. A 2007 World Cancer Research Fund review (PDF, 1.83Mb) concluded that garlic "probably protects against" bowel and stomach cancers. A more recent review from 2009 of the best available research on humans concluded there was "no credible evidence" with stomach, breast, lung and womb cancers, but that there was "very limited evidence" that eating garlic may lower the risk of colon, prostate, oral, ovary or renal cell cancers.
The dietitian's verdict
Alison Hornby, a dietitian and BDA spokesperson, says: "Garlic is a delicious flavour used widely in Mediterranean and Asian cooking.
"Studies using high concentrations of garlic extracts have been associated with improved blood circulation, healthier cholesterol levels and lower blood pressure, all of which reduce the risk of cardiovascular disease. However, current evidence does not support the use of garlic supplements to improve health.
"Garlic is particularly useful in cooking as it provides an alternative to salt in adding flavour to meals, along with lemon juice, chilli, herbs and spices. Eating less salt is important for avoiding high blood pressure."
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