For thousands of years garlic has been considered one of nature’s health foods. More recently, studies have shown that it does actually have an impact, improving blood pressure, cholesterol levels and immunity.
Garlic’s health benefits derive from the many natural compounds it contains, particularly allicin (also responsible for its pungent smell).
A 2018 review of studies by the University of Nottingham said that these benefits are ‘rooted in the sulphur compounds the plant absorbs from the soil which break down into around 50 different sulphur-containing compounds during food preparation and digestion’, which are ‘biologically active’ inside our cells.
Specifically these compounds seem to boost the body’s production of gaseous ‘signalling’ molecules, key to cell communication. Low levels of these molecules are associated with serious conditions including heart disease.
Indeed, a review of trials in the journal Experimental and Therapeutic Medicine in 2020 found that patients with high blood pressure given 600-900 mg garlic supplements for three months experienced a drop in their blood pressure that was similar to the effect of medication known as ACE inhibitors.
It’s thought that allicin stimulates the production of nitric oxide — which dilates blood vessels — as well as inhibiting ACE (angiotensin-converting enzyme) activity; this relaxes blood vessels and reduces blood pressure.
Garlic’s health benefits derive from the many natural compounds it contains, particularly allicin (also responsible for its pungent smell)
Laboratory studies also suggest allicin and other compounds in garlic have anti-viral properties.
However, Dr Jenna Macciochi, an immunologist at Sussex University, says there are only two ‘robust’ human trials: one found that people taking 180 mg of allicin for three months got fewer colds than a placebo group.
A second showed that taking 2.56 g of aged garlic extract improved immune cell function, which could reduce severity of cold and flu symptoms.
‘We can say that garlic does appear to play an immune-supporting and anti-viral role and may contribute to the reduced severity of colds, although eating a small amount as part of a meal might not provide enough of a dose to improve virus symptoms,’ says Dr Macciochi.
Aidan Goggins, a pharmacist and independent adviser to the supplement industry, says: ‘To get the therapeutic dose of around 900 mg [equivalent to 3-8 mg allicin] you need to eat around a clove of raw garlic every day.’
But it’s not as simple as just chucking some in your stir-fry.
Clare Thornton-Wood, a spokesperson for the British Dietetic Association, adds: ‘Allicin is only formed when the bulb is chopped or crushed.
‘Studies have found it stops forming as soon as it’s exposed to heat. So it’s a good idea to allow it to sit for around ten minutes after chopping to ensure the maximum allicin has been produced.
‘And don’t cook it for long. A 2018 study in the U.S journal Nutrients found that boiled garlic contained 16 per cent less allicin and roasted garlic 30 per cent less than raw.’ It’s also worth steering clear of pre-chopped garlic stored in oil or water, as there’s evidence it also has lower allicin levels, adds Aidan Goggins.
But can you get the health benefits from garlic supplements? Aidan Goggins assessed some of the latest products, which we then rated.
Holland & Barrett Odourless Garlic, 100 capsules for £6.99
Holland & Barrett Odourless Garlic
CLAIM: Containing 300 mg of ‘odourless’ garlic oil to ‘support heart health’ and ‘maintain healthy cholesterol levels’. Take up to six per day.
EXPERT VERDICT: ‘The concern I have with “odourless” garlic products is that it’s the formation of the allicin that creates the characteristic smell — so to create a non-smelly product will likely remove some of this chemical, along with its heart benefits,’ says pharmacist Aidan Goggins. ‘Garlic oil contains other health-boosting compounds including diallyl trisulfide, which a U.S. study in 2012 found may help protect the heart during cardiac surgery.
‘However, concentrated garlic oil is scientifically studied at a dose of 2-5 mg, and this contains only 0.6 mg of concentrated garlic oil per capsule, which is on the low side for noticeable effects.
‘You can take up to six per day, but that means the bottle will only last just over two weeks.’ 5/10
Healthspan Garlic 1,200 mg
Healthspan Garlic 1,200 mg, 120 tablets for £9.45, healthspan.com
CLAIM: ‘Containing ingredients your heart loves, a concentrated dose of 400 mg garlic powder, equivalent of 1,200 mg of fresh garlic [just over a third of a clove] with 1.1 mg vitamin B1 to support heart function.’ Take one per day.
EXPERT VERDICT: This is one of the higher doses of dried garlic powder available on the market — the form of supplementation that has been studied the most, with 600-900 mg considered the clinically effective dose. One tablet contains 400 mg [providing around 2 mg allicin] so two tablets a day would be needed.
Garlic powder tablets don’t contain allicin, because it will break down rapidly in a pill.
Instead they contain the precursor compound, alliin, and the enzyme, alliinase, which together react to form allicin when broken down in the stomach.
Garlic supplements should be taken with a meal, as eating lowers the overall acidity of the stomach and means more of the product survives — alliinase can be damaged by the concentrated acid in an empty tummy which could prevent allicin forming. This provides a good dose. 8/10
Sainsbury’s Odourless Garlic, 90 tablets for £2.45
CLAIM: These one-a-day tablets contain 3 mg of garlic extract and 1.1 mg vitamin B1, which ‘helps maintain heart function’.
EXPERT VERDICT: These tablets contain the equivalent of 300 mg of fresh garlic (one-tenth of a clove), which would provide around 2 mg alliin — this would be converted in the body to around 0.5 mg allicin, making it a low dose supplement.
It’s another ‘odourless’ product (see panel, left) and I struggle to understand what, if any, nutritional benefits are provided here. 1/10
Weightworld High Potency Garlic Oil, 180 capsules for £12.99, amazon.co.uk
CLAIM: ‘Each of our high strength garlic capsules delivers 30 mg of garlic oil extract, equivalent to 15,000 mg of odourless garlic oil.’ Take up to two a day.
EXPERT VERDICT: This product’s confusing description is all over the place. It claims to be odour-free, which generally means allicin has been removed, but it also says it has a high allicin content.
Saying the capsules deliver 30 mg of garlic oil extract, equivalent to 15,000 mg of odourless garlic oil makes no sense — does it mean 15,000 mg of fresh garlic, which is about four to five cloves?
Garlic oil is generally used clinically at a dose of 2–5 mg, so this is multiple times over that and could irritate the stomach.
Overall, I would steer clear of this badly labelled product. 0/10
Kwai Heartcare+ Japanese Black Garlic, 30 tablets for £5, boots.com
CLAIM: These tablets provide 450 mg black garlic, which ‘contains up to twice as many antioxidants as normal garlic’ and 30.8 mcg of vitamin B1 ‘to help maintain a healthy heart’. Take one per day.
EXPERT VERDICT: Studies have shown that black garlic has stronger antioxidant activity than normal garlic.
This is because polyphenols, or plant chemicals that protect our cells from damage, are released during their fermentation.
The polyphenol content of garlic can increase by up to tenfold aged in this way.
The trade-off is you’re hardly getting any allicin as most of it is destroyed during production. I wouldn’t recommend taking a black garlic supplement — just eat it! It’s available in supermarkets and has a sweeter, much gentler flavour than fresh garlic. 4/10
AllicinMax Powder Capsules, 30 for £4, boots.com
CLAIM: This provides ‘180 mg of stabilised allicin’ using ‘a patented extraction process which ‘locks in all its goodness’. Take one or two per day.
EXPERT VERDICT: Normal supplements contain no allicin — it has to be made in your body when you swallow garlic. This product claims to have overcome this issue by producing a form of stabilised allicin and, in theory, this is great because it means you’re not reliant on allicin being made in the body, with the risk that stomach acid stops some being formed.
At 180 mg it also appears to be a much higher allicin dose compared with a standard tablet or fresh garlic.
This could be a pretty exciting product, but I’d like to see more research on the method of stablising allicin. 8/10
Naturalma Bear’s Garlic Tincture
Naturalma Bear’s Garlic Tincture, 120 ml for £15.90, amazon.co.uk
CLAIM: Made from ‘bear’s garlic’ preserved in water and glycerine, this contains 200 mg per 2 ml dose. Take 40 to 120 drops per day diluted in water.
EXPERT VERDICT: Bear’s garlic (also known as wild garlic) is a different plant from standard garlic, with edible flowers and leaves with a garlic-like flavour.
It contains sulphur compounds similar to those in classic garlic and may have some similar effects — including as a herbal remedy for infections. But there haven’t been any robust studies, so there is no comparable medicinal dose.2/10
Horbaach Cod Liver Oil with garlic, 180 capsules for £12.99, amazon.co.uk
CLAIM: These capsules each contain 36 mg of omega-3 fish oils and 6 mg of odourless garlic oil. They ‘support heart, brain and eye health and maintain normal blood pressure’. Take one per day.
EXPERT VERDICT: The idea here is to combine two ingredients seen as good for heart health.
There has been some concern recently that omega-3 supplements raise ‘bad’ LDL cholesterol, so combining it with garlic, which we know lowers LDL, is seen as a way to counteract this.
However, you’re looking at pretty low doses of each nutrient here —so I’m not sure there will be much health benefit. 4/10