Garlic has long been prized as an aid to health and a treatment for a variety of ailments. Both raw and cooked garlic can be useful, depending on what’s wrong.
How you prepare the garlic influences the amounts and proportions of its bioactive compounds (see Chapter 2).
Some people chew a fresh raw clove each day, though the release of sulfenic acid and allicin when chewing is fairly bracing! Other people add raw garlic to foods such as salad dressings (see page 61) or bruschetta (see page 48). You could drink hot water to which you have added a crushed clove, 1–2 teaspoons of honey and a squeeze of lemon juice.
How you cook garlic is important, too (see page 31).
Garlic supplements also vary in the amounts and proportions of their bioactive ingredients (see page 22). For recipes for garlic oilmacerate and garlic syrup, see pages 37 and 40 respectively.
This table summarizes the bioactivity of garlic’s sulfur compounds:
| Bioactivity | Water-soluble compounds | Oil-soluble compounds |
| Antioxidant and therefore anti-inflammatory | Yes | Yes |
| Cholesterol-lowering | Yes | Yes |
| Smooth-muscle relaxing | Yes | Yes |
| Anti-obesity | Yes | Yes |
| Anti-clotting | No | Yes |
| Anti-diabetic | No | Yes |
| Anti-microbial | No | Yes |
| Detoxifying | No | Yes |
| Immunity-enhancing | No | Yes |
The nature and extent of this bioactivity depend on whether garlic is raw or cooked and how it is prepared, or on the type of supplement:
To get both water- and oil-soluble compounds, consume:
• Crushed or chopped garlic that you have left to stand for 30–60 minutes before eating it, mixing it with lemon juice or vinegar, or cooking it.
• A garlic-powder supplement with a high allicin yield.
To get mainly oil-soluble compounds, consume:
• Chopped or crushed garlic that has stood for 90 minutes before being eaten, mixed with lemon juice or vinegar, or cooked.
• A garlic-oil supplement if you particularly want diallyl disulfide and diallyl trisulfide.
• Garlic oil-macerate if you particularly want ajoene and vinyl dithiins.
Note that when garlic, garlic oil, garlic oil-macerate or garlic water (see page 41) are applied to the skin, their bioactive sulfur compounds not only act on local skin cells but are also absorbed into the tissue fluid and hence into the capillaries (tiny blood vessels) and tiny lymph vessels. They are then transported around the body.
The World Health Organization advises that adults can promote health by taking one of the following each day:
• ½–1 medium clove of fresh garlic. Eat this with food – for example, crushed into a salad dressing; in warm water with honey; or added to other food towards the end of the cooking time. Allicin release begins on crushing or chopping garlic and peaks 90 minutes later. You get a good balance of water- and oil-soluble sulfur compounds if you leave chopped or crushed garlic to stand for 30–60 minutes before use.
• 0.4–1.2g garlic-powder product.
• 300–1,000mg garlic extract.
• 2–5mg garlic oil.
• Any garlic product supplying 2–5mg allicin.
Studies have found no adverse effects from eating 3–5 medium cloves a day. One study found no serious adverse effects from consuming up to 15 cloves a day for 3 months.
Garlic has powerful biological effects, so if you are considering using it, note the following advice.
• Skin problems – do a patch test first by applying garlic to a small inconspicuous area and checking after several hours that it has not caused any irritation. Do not apply again if it has. Garlic oil lacks garlic’s irritating agents (sulfenic acids and allicin) but also lacks the bioactivity of allicin and its derivatives. Be very wary of applying garlic to a child’s skin.
• Vaginal or rectum/anal problems – do not use garlic locally, as it could irritate or burn.
• Stomach or digestive problems – note that large amounts of garlic can irritate the stomach and intestine.
• Bleeding disorders – note that garlic can encourage bleeding. This effect can be exaggerated by also consuming any other herb or supplement that slows blood-clotting, including fish oil, vitamin E, angelica, cloves, ginger, ginkgo, red clover, turmeric and willow.
• Pregnancy – note that normal dietary amounts of garlic are likely to be safe for the baby, but it is wise to avoid large amounts and not to apply garlic to your skin. If you are due to give birth within 2 weeks, large intakes of garlic might encourage bleeding during childbirth or associated surgical procedures.
• Breastfeeding (nursing) – avoid consuming or applying large amounts of garlic, because there are insufficient data to confirm their safety for the baby. Babies spend longer breastfeeding after their mothers have eaten garlic, probably because they like garlic-scented breast milk.
• Awaiting surgery – avoid garlic for 2 weeks before scheduled surgery, because it can prolong bleeding.
• Chronic heavy drinking – avoid consuming large amounts of garlic, because this could slow the breakdown of the liver’s P450 2E1 enzyme, which helps to break down alcohol.
• Taking oral contraception (‘the Pill’) containing estrogen – note that garlic could speed its breakdown and endanger birth control. If you consume a lot of garlic, consider using additional birth control (such as a condom).
• Taking ciclosporine (an immunity-suppressor) – note that allicin-containing garlic products can decrease its efficacy.
• Taking medications affected by cytochrome P450 enzymes, such as paracetamol (acetaminophen); calcium-channel blockers for high blood presssure (such as nicardipine), losartan (for high blood pressure), certain anti-cancer drugs (such as paclitaxel), certain anti-fungals (such as ketoconazole), cortisol and other glucocorticoids (for allergy and autoimmune disease), chlorzoxazone (a muscle-relaxant), theophylline (for certain respiratory disorders), fentanyl (a pain-reliever), midazolam (for epilepsy), lidocaine (a local anaesthetic and a heart medication) and certain anaesthetics (such as halothane) – note that garlic can slow the breakdown of these medications, so increasing their effects. Discuss with your doctor whether to avoid or cut back on garlic.
• Taking high-blood-pressure medication with a calcium-channel blocker (such as verapamil) – note that garlic’s mild blood-pressure-lowering effects might increase their action. Be sure to have regular blood-pressure checks.
• Taking anti-clotting medication (such as aspirin and warfarin) – note that garlic could further reduce clotting, encouraging bruising and bleeding, though small amounts of garlic are unlikely to be a problem. If you are on warfarin, be sure to have regular blood tests.
• Taking blood-sugar-lowering medication – note that garlic may further lower blood sugar, though normal amounts of garlic are unlikely to be a problem.
• Taking the anti-TB drug isoniazid – note that you should avoid garlic, because it could reduce the drug’s absorption.
• Taking HIV/AIDS medications called non-nucleoside reverse transcriptase inhibitors (such as nevirapine); also, saquinavir as your only protease inhibitor – discuss with your doctor whether to avoid garlic.
Garlic’s oil-soluble sulfur compounds can cause the following:
• Burning mouth, heartburn, nausea, vomiting, wind, diarrhoea and appetite loss after consuming raw garlic or garlic oil on an empty stomach.
• Faintness, flushing, headache, dizziness, sweating, rapid pulse and insomnia.
• Redness, burning and blisters from prolonged use on the skin.
• Haemolytic anaemia after eating a large amount of raw garlic.
In addition, garlic can cause allergic reactions such as allergic contact dermatitis, allergic rhinitis (‘hay fever’), asthma and anaphylaxis (rare but potentially fatal mouth and throat swelling, breathing difficulty and shock, which require urgent treatment with medically prescribed adrenaline). Allergic reactions are most likely in those people who work with garlic. Diallyl disulfide is often to blame because it penetrates most protective gloves. Another potential culprit is alliinase. Cross-sensitivity to other alliums or to Liliaceae plants (such as lilies, ginger and bananas) may also occur.
Scientists have investigated garlic more than almost any other medicinal plant, but their studies have involved many different garlic preparations or supplements, in many different doses. Also, the numbers of volunteers involved in such trials are often small. So for most disorders it is not possible to say for sure whether garlic helps or, if it does, what preparation or supplement, at what dose, is best.
To learn more about any of the studies mentioned here, enter keywords and the journal’s name and year of publication into an internet search engine.
The actions I suggest should not take the place of a proper medical diagnosis and therapy. If in any doubt, see your doctor.
Skin needs adequate dietary sulfur to remain healthy, and many people are sulfur-deficient. Garlic’s sulfur compounds might help. Also, its antioxidants reduce inflammation, and its sulfur compounds may kill acne bacteria.
Action: Do a patch test (see page 87).
Rub affected skin with the cut surface of a garlic clove twice a day. Alternatively, bathe the area with garlic water (see page 41) twice a day. Include garlic in your daily diet or take a garlic-powder supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic’s antioxidants discourage memory loss and other brainpower decline by helping prevent oxidation of fatty acids, hormones and certain other substances in the brain. Garlic may also discourage artery disease, detoxify certain potentially damaging nerve-cell toxins, and encourage excretion of aluminium, lead and other heavy metals that can damage the brain.
Aged garlic extract increased memory and learning ability in mice prone to early ageing. It also discouraged degeneration in the brain’s frontal lobes. Nerve cells grew better too, suggesting enhanced memory.
Phytotherapy Research, 1996
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Possible culprits include inflammation that encourages oxidation of brain fats, and high levels of the amino acid homocysteine. A lack of B vitamins raises homocysteine, and sufferers are particularly likely to go short of this vitamin. Garlic’s anti-inflammatory antioxidants and B vitamins may help.
In Alzheimer’s-prone mice, aged garlic extract helped prevent early memory loss.
Phytotherapy Research, 2007
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Atherosclerosis is a condition characterized by narrowing of the arteries by fatty atheroma plus stiffening of their walls by inflammation-induced scarring and calcium deposition. It is encouraged by smoking, diabetes and high blood pressure, cholesterol and trialglycerol blood fats, and an unhealthy diet and lifestyle factors that promote inflammation. At worst, a patch of atheroma ruptures, triggering a clot or bleed that causes a stroke or heart attack.
Atherosclerosis can also cause poor circulation, encouraging thin dry skin, cold feet, leg pain on walking, impotence and dementia. Garlic is a traditional remedy; indeed:
A research review at Liverpool John Moores University suggests that the more garlic that’s eaten, the less likely is artery disease to progress.
Journal of Nutrition, 2006
Scientists believe that garlic may have protective effects because various water- and oil-soluble sulfur compounds are anti-inflammatory and also boost hydrogen sulfide and inhibit ACE (see page 93) – which reduces blood pressure by expanding arteries.
In addition, they think that garlic’s:
• allicin derivatives produce nitric oxide, which reduces blood pressure by relaxing smooth muscle in artery walls; they also help to counter atheroma;
• gamma-glutamyl cysteines act like ACE- (angiotensin-converting enzyme) inhibitors, a family of drugs used for high blood pressure, heart failure and strokes;
• antioxidants discourage oxidation of LDL cholesterol, and inflammation;
• manganese aids certain antioxidant enzymes and boosts HDL cholesterol (the protective type); and
• S-allyl cysteine acts like a statin (a drug used to combat high cholesterol); and its Vitamin B6 lowers levels of the amino acid homocysteine (which can damage artery walls).
Garlic has antioxidant and blood-pressure-reducing effects. It may have modest anti-clotting and cholesterol- and trialglycerol-reducing effects, too. It may also help ageing arteries remain stretchy. For example:
An Indian study reports that garlic given to mice on a fatty diet reduced blood cholesterol. Garlic also acted like statin drugs in that it blocked the enzyme (hydroxyl-methyl-glutaryl Co-A reductase) necessary for cholesterol production in the liver.
British Journal of Nutrition, 2009
An Iranian study found that garlic extract strongly inhibited angiotensin-converting enzyme (ACE) production. ACE-inhibition is known to lower blood pressure by reducing angiotensin II and bradykinin. It also reduces extra-cellular fluid by diminishing secretion of the hormone aldosterone. All this would reduce high blood pressure and so help to prevent heart failure.
Pathophysiology, 2007
Giving garlic extract to volunteers with arteriosclerosis (stiffened arteries) for 6 months reduced oxidation in their blood. Garlic boiled for 20 minutes had the same effect as raw garlic.
Life Sciences, 2006
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Early evidence suggests that garlic’s anti-inflammatory antioxidants benefit arthritic joints.
A UK study of more than 1,000 women found osteoarthritis of the hip was less likely in those whose diet was high in garlic and other alliums. Also, in the test tube, diallyl disulphide reduced levels of cartilage-damaging enzymes.
BMC Musculoskeletal Disorders, 2010
Action: Include garlic in your daily diet or take a garlic supplement. You need both water- and oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy for asthma, and early evidence suggests that its anti-inflammatory antioxidants (such as quercetin) may help. It may also help in other ways:
Allicin-containing garlic extract relaxed smooth muscle in rats’ windpipes. Aspirin and indomethacin, which inhibit the production of certain prostaglandins (hormone-like substances), reduced this relaxation. The conclusion was that garlic extract relaxed smooth muscle by stimulating the release of these prostaglandins.
Pharmacognosy Magazine, 2011
A study in Iran reports that giving aged garlic extract to mice with allergic airway inflammation decreased inflammation around the airways and blood vessels. It also decreased eosinophil white cells and immunoglobulin-1 antibodies, which are biochemical markers of allergy.
Iranian Journal of Allergy, Asthma and Immunology, 2008
Action: Include fresh garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is an anti-fungal agent, and several studies have found that garlic, or ajoene alone, is useful. For example:
A study of 50 people with athlete’s foot, in New Jersey, compared one week’s twice-daily applications of a 1 percent ajoene solution or the anti-fungal medication terbinafine. Garlic had a 100 percent cure rate, terbinafine 94 percent.
Journal of the American Academy of Dermatology, 2000
Action: Do a patch test (see page 87).
As ajoene cream and gel are not available commercially, apply garlic oil-macerate or garlic oil with a cotton-wool (cotton) ball twice a day. Maximize the content of allicin derivatives in homemade garlic oilmacerate by leaving newly crushed garlic to stand for 90 minutes before adding oil.
Alternatively, bathe the infected area with garlic water (see page 41).
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds and, in particular, ajoene (see page 13).
Test-tube and animal studies reveal anti-inflammatory, detoxifying, immunity-stimulating and anti-infective properties for garlic sulfur compounds excreted through the lungs. They also show that certain garlic ingredients have the potential to break down bacterial biofilms, and to relax smooth muscle in airway walls – which would expand them and so increase air-flow.
Garlic syrup is an expectorant (encourages coughing-up of phlegm).
Garlic is also a traditional remedy for pneumonia, and studies suggest it can help viral pneumonia.
It isn’t yet certain if garlic is useful for bronchitis and pneumonia, but it is worth a try.
Action: Take 1–3 teaspoons garlic syrup three times a day to help you cough up phlegm.
Alternatively, include garlic in your daily diet or take a garlic supplement. Note that you need oil-soluble sulfur compounds (see page 85).
Further options are: crush several garlic cloves, wait 30 minutes, then inhale the vapour from up to 20cm/8in away; repeat several times a day. Any initial stinging in the nose should quickly abate; if not, or if it is excessive, inhale from further away or take garlic another way.
Alternatively, do a patch test (see page 87). Rub garlic oil over your chest.
Garlic is a traditional remedy, and preliminary studies suggest it reduces the risk of several cancers, especially those of the mouth, gullet, stomach and bowel.
Test-tube studies suggest it could help prevent or treat cancer by:
• discouraging oxidation and chronic inflammation;
• enhancing immunity;
• killing bacteria and viruses;
• influencing certain hormones;
• detoxifying certain cancer-causing agents, blocking their formation, or halting their activation; and
• reducing cancer-cell multiplication, helping to prevent them becoming invasive, or promoting their suicide (apoptosis).
For example:
A test-tube study of the effects of 34 vegetable extracts on 8 types of cancer-cell found that garlic was by far the strongest inhibitor of their multiplication. It didn’t inhibit the multiplication of normal cells.
Food Chemistry, 2009
A German study found that steeping raw meat in a garlicky marinade greatly reduced the content of cancer-encouraging heterocyclic amines in the cooked meat.
Journal of Agricultural and Food Chemistry, 2007
Test-tube research found that a garlic lectin (sugar-binding protein) strongly reduced cancer-cell multiplication and induced apoptosis.
Food Research International, 2001
However, studies in people paint a much less rosy picture – as, for example, in the following review (although the number of studies good enough to be selected for the review was relatively small, as were the numbers of people studied):
A review of 19 selected trials in 1955–2007 found no credible evidence for a relation between garlic intake and a reduced risk of breast, lung, stomach or womb cancer. Also, only very limited evidence supported a relation between garlic intake and a reduced risk of colon, gullet, kidney, larynx, mouth, ovary or prostate cancer.
American Journal of Clinical Nutrition, 2009
Action: Hedge your bets by including garlic in your daily diet or taking a garlic supplement. You need water– and oil-soluble sulfur compounds (see page 85).
In the test tube, at least, Herpes simplex virus type 1, which causes cold sores, is sensitive to allicin and its derivatives, in particular ajoene.
Action: Do a patch test (see page 87).
Smear a little petroleum jelly (‘Vaseline’) on to the skin around the sore, then apply a sliver cut from a garlic clove and leave it for as long as it will stay there; repeat twice a day.
Alternatively, apply the oil from a garlic oil-macerate to the sore several times a day. These methods also exclude air from the sore, which is helpful.
Another option is to bathe the infected area with garlic water (see page 41).
A final option is to apply allicin cream. Any stinging and smell soon go.
In addition, include garlic in your diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy. Any success is probably because of its anti-microbial, anti-inflammatory and immunity-enhancing compounds. For example, test-tube studies show that Parainfluenza virus type 3 and Human rhinovirus type 2 are sensitive to garlic.
This study suggests that garlic helps to prevent and treat colds:
146 volunteers took either an allicin-containing garlic supplement or a placebo (dummy medication) for 12 weeks in winter. Those taking garlic had only 24 colds while those who took the placebo had 65; also, those [colds] they had were shorter and their chances of re-infection were reduced.
Advances in Therapy, 2001
Action: Take garlic in honey, because garlic is powerfully antiseptic, while honey is soothing and healing. To do this, crush 10 garlic cloves, then leave to stand for 10–90 minutes before stirring the garlic into a 450g/1lb jar of clear honey. Take 1 teaspoon every 2 hours.
Alternatively, take a teaspoon of garlic syrup (see page 40) every 2 hours.
Alternatively, crush several garlic cloves, then wait for 30 minutes before inhaling the fumes from up to 20cm/8in away. Repeat several times a day. Any initial stinging in the nose should quickly abate, but if not, or if it is excessive, inhale from further away or take garlic in another form.
Alternatively, take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Alternatively, take a pure-allicin supplement.
Take a warm garlic bath (see page 41).
For a sore throat, gargle with garlic water (see page 41).
Research suggests that garlic can help tense smooth-muscle cells to relax (see ‘Asthma’). So it might also help period pain or intestinal colic.
Action: Include garlic in your daily diet or take a garlic supplement. You need both water- and oil-soluble sulfur compounds (see page 85).
Those of garlic’s anti-inflammatory and anti-microbial agents that make it to the bladder may help to counter a urine infection. Also, it is possible, though unproven, that garlic’s smooth-muscle-relaxing properties might help to relax cystitis-like symptoms caused by unusually tense smooth muscle in the bladder wall.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Scalp flaking is often associated with infection with the fungus Malassezia furfur. Garlic’s anti-fungal activity means it might be effective.
Action: Do a patch test (see page 87).
Apply garlic water (see page 41) to your scalp, cover with a towel for 1 hour, then rinse off the bits of garlic before shampooing. Repeat once or twice a week.
Alternatively, mix 2 crushed cloves of garlic with a tablespoon of coconut oil. Use the mixture to massage your scalp for 5 minutes, then cover with a hot towel for 20 minutes before shampooing.
Alternatively, massage your scalp with garlic oil, then continue as above.
Alternatively, use a garlic shampoo and conditioner (available on the internet).
Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Many studies show that raw garlic reduces blood sugar in animals with type-2 diabetes (the common sort). Researchers attribute this to allicin and its derivatives. For example, garlic oil and diallyl trisulfide improved blood sugar in diabetic rats by increasing insulin release and reducing insulin resistance:
In an Indian study, rats were given a diet of 65 percent fruit sugar (which induces type-2-diabetes); or 65 percent fruit sugar and raw garlic; or a ‘control’ diet of 65 percent cornstarch [cornflour]. After 8 weeks, the fruit-sugar group had higher blood sugar, insulin and insulin resistance than the controls, but the gains were lower in those that had consumed garlic.
Nutrition, Metabolism and Cardiovascular Diseases, 2011
It is not yet known whether garlic helps to prevent or treat diabetes in humans, but research suggests it might help to prevent diabetes-associated heart disease, which is responsible for most deaths in people with diabetes.
Action: Until we know more, include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic’s allicin and certain of its derivatives (such as diallyl disulphide) can kill bacteria such as Escherichia coli and salmonellae, which can cause gastroenteritis. Garlic can also help to cure diarrhoea caused by infection with the protozoon Cryptosporidium.
In addition, garlic can help to relieve diarrhoea associated with antibiotics, or irritable bowel syndrome, by restoring a normal balance of gut bacteria.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy. Early research suggests that it promotes exercise endurance. Also, garlic promotes production of hydrogen sulphide and nitric oxide, both of which relax arteries, so increasing blood flow to muscles. This enhances energy, post-exercise recovery and muscle growth.
A study in which rats did endurance exercise 5 times a week found that giving aged garlic extract 30 minutes beforehand facilitated aerobic sugar metabolism, reduced oxidation and, by widening arteries, promoted the muscles’ oxygen supply.
Biological & Pharmaceutical Bulletin, 2006
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy in certain countries.
An Iranian study found that garlic extract strongly inhibited the formation of angiotensin-converting enzyme (ACE). ACE-inhibition is known to reduce fluid retention by diminishing secretion of the hormones aldosterone and anti-diuretic hormone.
Pathophysiology, 2007
A study in Chile found that garlic-powder capsules increased urine production in dogs. The effects were dose-dependent, peaked within 40 minutes and fell to their initial levels within 2½ hours.
Journal of Ethnopharmacology, 1991
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic has been claimed to increase bile flow. If so, it would discourage gallstones, which occur when bile stagnates in the gallbladder. What’s more, garlic is rich in antioxidants, which, studies suggest, discourage gallstones. Garlic may also have a cholesterol-lowering effect in both blood and bile.
Researchers in India found that when mice on a gallstonepromoting diet were given raw or cooked garlic, the bile’s cholesterol concentration was reduced and gallstones discouraged. Raw garlic was the most effective.
British Journal of Nutrition, 2009
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy. Any success probably stems from its anti-inflammatory and anti-histamine constituents.
Action: Eat more garlic or take a garlic supplement in the weeks before and during your usual hay-fever season. You need water- and oil-soluble sulfur compounds (see page 85).
Heart attacks are encouraged by atherosclerosis (see ‘Artery disease’, page 92), chronic infection (see ‘Infection’, page 111), diabetes (see page 102), high blood pressure (see page 108), a tendency to inflammation (see page 112) or blood-clotting (see below) and high cholesterol (see page 109). Garlic may help to prevent these. It has certainly been noted that people who eat a lot of garlic tend to have lower rates of coronary heart disease – though this does not, of course, constitute proof.
Test-tube studies show that garlic can decrease blood-clotting by:
• making tiny particles in blood (platelets) less sticky and less likely to clump together to form a blood clot;
• boosting nitric-oxide production (this ability is retained by heat-treated and aged garlic products);
• decreasing blood sugar (this is helpful because sugary blood is more likely to clot); or
• decreasing fibrinogen (high levels of this blood-clotting protein encourage clots; they also rise during inflammation).
A review of randomized controlled trials done between 1966 and 2000 found that garlic modestly decreased platelet clumping in the test tube.
Archives of Internal Medicine, 2001
An Argentinian study found that 6–10 minutes of boiling in water, or oven-heating, destroyed the anti-platelet-clumping ability of whole garlic and reduced that of crushed garlic. However, more than 10 minutes of either treatment destroyed this anti-clotting ability, as did microwaving. The researchers conclude that crushing garlic before cooking it for a short time helps to conserve some anti-clotting ability.
Journal of Agricultural and Food Chemistry, 2007
Garlic may also make permanent damage from a heart attack less likely:
A study at the University of Connecticut gave freshly crushed garlic, roasted garlic, or no garlic, to rats for 30 days. The blood supply to the heart was then reduced for 30 minutes. Both types but particularly the freshly crushed garlic helped prevent heart damage. This also increased certain anti-inflammatory factors, thanks to hydrogen-sulphide production.
Journal of Agricultural and Food Chemistry, 2009
In addition, garlic may discourage abnormal heart rhythm after a heart attack (or, indeed, at any other time). But while garlic does help to prevent clots in the test tube, several small studies suggest that it does not work for people; for example:
A study of 14 volunteers found little or no effect on plateletclumping 4 hours after taking capsules of garlic oil-macerate.
Wojcikowski, 2007
Action: Until we know more, include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Research suggests that this traditional remedy reduces high blood pressure (defined as more than 140/90mmHg). Falls in blood pressure produced by taking garlic compare with those from common blood-pressure medications (such as beta-blockers and ACE inhibitors). For example:
In a study at the University of Adelaide, Australia, 50 volunteers with high blood pressure despite medication were put into two groups. One took aged garlic extract plus their medication for 12 weeks; the other just their medication. Those on garlic had an average fall of 10 mmHg in their systolic blood pressure (the upper of a reading‘s two figures).
Maturitas, 2010
A review of 10 good studies up to 2008 found that garlic reduced high systolic blood pressure by 16 mmHg and reduced diastolic blood pressure (the lower of a reading’s two figures) by 9 mmHg, compared with a placebo (dummy medication).
Annals of Pharmacotherapy, 2008
The numbers of people that have been studied are relatively small. However, if garlic does indeed help, this is probably because it:
• discourages atherosclerosis (see ‘Artery disease’);
• contains gamma-glutamyl cysteines – natural angiotensin-converting enzyme inhibitors (ACE inhibitors) that reduce blood pressure by expanding arteries;
• releases hydrogen sulphide (from polysulfides in chopped or crushed raw garlic), which expands arteries;
• promotes nitric oxide production, which expands arteries (this ability is retained by heat-treated and aged garlic products);
• has prostaglandin-like effects, which reduce blood pressure by relaxing smooth muscle in artery walls; and
• contains substances that activate sodium-pump enzymes, which maintain low sodium levels in cells.
In addition, one small study suggests that vitamin C enhances garlic’s blood-pressure-lowering effect. Also, studies suggest that this effect lasts for up to 24–48 hours.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Eat plenty of vitamin-C-containing foods.
High levels of low-density lipoprotein (LDL) cholesterol and total cholesterol, and a low level of high-density-lipoprotein (HDL) cholesterol, plus a lifestyle that encourages oxidation of LDL cholesterol, encourages heart attacks and strokes. Scientists have found that low HDL cholesterol is four times better at predicting heart attacks than high LDL cholesterol, and eight times better than high total cholesterol.
Many studies in the 1980s and early 1990s suggested that garlic might help to inhibit cholesterol production, increase cholesterol excretion and protect LDL cholesterol from oxidation.
Since then, though, high-quality studies have suggested that garlic does not help significantly. So current medical opinion is that garlic is ‘possibly ineffective’.
In a US trial, 192 adults with raised total and LDL cholesterol took raw garlic, powdered garlic, aged garlic extract, or a placebo (dummy medication) 6 days a week for six months. The daily garlic dose equated to a medium-sized clove. None of the three types of garlic had significant effects on cholesterol.
Archives of Internal Medicine, 2007
However, it’s just possible that certain formulations of supplement could have positive effects. For example:
In a Russian study, 42 men with mildly high cholesterol took timed-release garlic-powder tablets for 12 weeks. There was a moderate decrease in total and LDL cholesterol, and an increase in HDL cholesterol.
Journal of Atherosclerosis and Thrombosis, 2008
Action: Until we know more, include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is a traditional remedy.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85), though stop if either worsens your indigestion.
Garlic has been used for millennia to treat infections. In World War II, garlic became known as ‘Russian penicillin’ because the new antibiotics were in short supply and Red Army physicians used garlic instead. Today, garlic remains a popular anti-infective agent worldwide. Indeed, many Russian hospitals still use the vapour of freshly chopped garlic to combat infection.
Test-tube studies show the following:
• Garlic has anti-bacterial effects against bacilli, brucellae, enterobacter, mycobacteria, pseudomonas, staphylococci, streptococci and vibro bacteria as well as Campylobacter jejuni, Cryptococcus neoformans. Enterococcus faecalis, Escherichia coli, Helicobacter pylori, Klebsiella pneumoniae, Neisseria gonorrhoeae, Proteus vulgaris and Salmonella enteritidis. Allicin-containing supplements may help to cure infections caused by the ‘superbug’ methicillin-resistant Staphylococcus aureus (MRSA). Bacteria can become resistant to antibiotics but not to garlic.
• Garlic has anti-viral effects against coxsackie viruses and human cytomegaloviruses, as well as Herpes simplex types 1 and 2, Human immunodeficiency virus type 1, Human rhinovirus type 2, Influenza virus type B, Parainfluenza virus type 3, Vaccinia virus and Vesicular stomatitis virus. Garlic may also enhance the efficacy of ’flu vaccine.
• Garlic has anti-fungal effects against aspergillus, microsporum and trichophyton as well as Cryptococcus neoformans, Pneumocystis jirovecii and various yeasts, including the yeast-like fungus Candida albicans. Garlic can be more potent than certain anti-fungal medications, including amphotericin B, gentian violet, griseofulvin, ketoconazole and nystatin.
• Garlic has anti-protozoal effects against cryptosporidia, Entamoeba histolytica, Toxoplasma gondii and various types of plasmodium (which causes malaria).
Few studies have been done in people to compare garlic with antibiotics, anti-viral, anti-fungal or anti-protozoal drugs. However, it would seem that garlic is well worth trying along with such drugs or (for an infection that isn’t serious) on its own.
Action: To help prevent or treat infection, include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Many garlic constituents have antioxidant or other anti-inflammatory actions. These include its flavonoids, saponins and many of its sulfur compounds. This helps to explain its reputation for helping to treat diseases that involve inflammation, such as allergy, Alzheimer’s, arthritis, asthma, atherosclerosis, cancer, diabetes, eczema, hay fever, heart attacks, infection, inflammatory bowel disease, metabolic syndrome, multiple sclerosis, osteoporosis, psoriasis and strokes.
A Canadian test-tube study shows that sulfenic acid (produced from alliin by the enzyme alliinase) is the fastest antioxidant ever seen. The researchers believe this helps explain garlic’s medicinal benefits.
Angewandte Chemie, 2009
A research review at the University of Texas notes that many inflammatory diseases have been linked with activation of an inflammation-inducing substance called nuclear transcription factor kB. The pathway that activates this factor can be interrupted by substances derived from various spices and herbs, as well as by diallyl sulfide, S-allylmercaptocysteine and ajoene from garlic. This, they say, ‘provides reasoning for seasoning’.
Annals of the New York Academy of Sciences, 2004
However, a study in people with pro-inflammatory risk factors found that garlic had no effect on commonly measured biomarkers of inflammation:
In a study of 90 overweight smokers, taking a daily garlic-powder supplement did not reduce these biomarkers of inflammation.
American Journal of Clinical Nutrition, 2006
Action: Until we know more, include garlic in your daily diet by taking a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
This syndrome (also called pre-diabetes or syndrome X) greatly encourages diabetes, heart disease and strokes, affects one in five adults and is defined by having three of more of these factors:
• Insulin resistance.
• ‘Apple-shaped’ body, with fat around the waist.
• High blood pressure.
• High blood fats.
• Low HDL-cholesterol (the protective sort).
Researchers suspect that inflammation and oxidation play a part. It is certain that affected people are prone to high levels of C-reactive protein, indicating inflammation. Recent research suggests that garlic discourages metabolic syndrome:
In an Indian study, rats ate a diet of 65 percent fruit sugar (a diabetes-inducing diet), or a diet of 65 percent fruit sugar and raw garlic, or a control diet of 65 percent cornstarch (cornflour). After 8 weeks, both the fruit-sugar groups had raised blood sugar, insulin, trialglycerols, uric-acid and insulin resistance. But these gains were lower in the group that also consumed garlic. The conclusion was that garlic improves insulin sensitivity and metabolic syndrome in rats on a diabetes-inducing diet.
Nutrition, Metabolism and Cardiovascular Diseases, 2011
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Also called aphthous ulcers or canker sores, these can be extraordinarily painful.
Action: Do a patch test (see page 87).
Dab an ulcer with the cut end of a garlic clove several times a day. But don’t repeat this if the pain worsens the first time.
Include raw garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic may help to treat a fungal nail infection.
Action: Do a patch test on the adjacent skin (see page 87).
Apply garlic oil (for example, from a garlic perle) to the infected nail and adjacent skin 2 or 3 times a day for 6 months for fingernails, or a year for toenails. Alternatively, use the oil from garlic oil-macerate (see page 37).
Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Some people with nerve pain such as trigeminal neuralgia report that repeated applications of garlic to the painful area are helpful. Garlic might work by producing hydrogen sulfide and nitric oxide, which expand arteries, thus improving the blood supply to nerves. Garlic might also help by supplying anti-inflammatory compounds. In addition, its allixin is said to encourage nerve growth and wellbeing.
However, if pain results from pressure on a nerve, as with sciatica, garlic is unlikely to help.
Action: Do a patch test (see page 87).
Apply the garlicky oil from a garlic oil-macerate (see page 37) to the painful area several times a day. Maximize the content of allicin derivatives in homemade garlic oil-macerate by leaving the newly crushed garlic to stand for 90 minutes before adding the oil.
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic is reputed to aid weight loss. Early research suggests that it might help by:
• encouraging heat production by brown fat (metabolically active fat between the shoulder-blades), stimulating the breakdown of trialglycerol blood fats;
• inactivating gastric lipase, an enzyme needed for fat digestion;
• reducing appetite;
• making pre-adipocytes (fat-cell precursors) less likely to develop into adipocytes; and
• reducing the fat absorbed from a meal.
For example:
In an Indian study, rats were fed a diet of 65 percent fruit sugar (which induces type-2-diabetes), or a diet of 65 percent fruit sugar and raw garlic, or a ‘control’ diet of 65 percent cornstarch [cornflour]. Those given fruit sugar and garlic gained less weight over 8 weeks.
Nutrition, Metabolism and Cardiovascular Diseases, 2011
French researchers report that vinyl dithiin made pre-adipocytes less likely to accumulate fat or produce inflammatory molecules (such as interleukin-6).
Journal of Nutrition, 2009
Japanese researchers report that rats on a high-fat diet given a garlic-powder supplement for 28 days lost weight. The garlic increased their adrenaline and noradrenaline – hormones that stimulate trialglycerol metabolism and are thought to boost heat production in brown fat. Garlic also increased uncoupling protein – which similarly increases heat production in brown fat. The researchers also report that alliin, diallyl disulfide or diallyl trisulfide increased adrenaline and noradrenaline.
Journal of Nutrition, 1999
This study found that garlic’s ajoenes inactivate gastric lipase, the enzyme needed for digestion of fats.
Biochimica et Biophysica Acta, 1989
Action: Until we know more, include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Research suggests that inflammation and oxidation play an important part in this bone-thinning condition, in which case garlic’s anti-inflammatory antioxidants might help.
Action: Until we know more, include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
A peptic ulcer can develop if something interferes with the stomach’s protective mucus, lining or acid. Contrary to popular belief, most people with ulcers do not make too much acid. In fact, many make too little. Inflammation caused by infection with Helicobacter pylori bacteria is a major cause, and these bacteria are becoming increasingly resistant to antibiotics. While garlic has anti-bacterial properties in the test tube, giving garlic to people with a peptic ulcer who are infected with these bacteria does not help. So the current thinking is that garlic may be ineffective.
Action: Until we know more, include garlic in your daily diet or take a garlic supplement, but stop if your symptoms worsen. You need water- and oil-soluble sulfur compounds (see page 85).
Piles occur when spongy pads in the walls of the back passage enlarge. They then readily become inflamed, triggering itching, bleeding and discomfort. Possible causes include constipation and fragile veins. Garlic might help because of its anti-inflammatory compounds, fibre (which helps prevent constipation) and vitamin C and flavonoids (which strengthen veins).
Inserting garlic into the back passage is a traditional remedy that is best avoided as it can irritate or burn.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is known as a ‘warming’ herb because it expands arteries, so boosting circulation. It may also help to prevent or treat artery disease. It also makes blood less sticky, which aids blood flow.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Early studies confirm the common belief that garlic boosts immunity, showing, for example, that it influences several sorts of white cell by:
• stimulating the ability of natural killer cells to destroy virus-infected and cancer cells;
• increasing the activity of macrophages (which engulf foreign bacteria);
• activating helper-T cells (which encourage the growth and activation of cytotoxic or ‘cell-killer’ T cells);
• maximizing the bactericidal activity of macrophages; and
• influencing the sorts of antibodies produced by B cells.
Action: Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic’s vitamin C and other antioxidants help to counter early ageing of skin, joints and arteries and reduce inflammation associated with heart disease, arthritis and Alzheimer’s. Garlic may also discourage certain cancers and strokes. Finally, pectin in the garlic-clove skin helps to eliminate from the body heavy metals such as aluminium and lead, which encourage cells to age prematurely.
In mice prone to early aging, aged garlic extract increased lifespan.
Phytotherapy Research, 1996
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Preliminary evidence suggests that garlic might improve urine flow and make urination less frequent in men with benign prostate enlargement.
Action: Until we know more, include garlic in your daily diet or by taking a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
This condition causes patches of thick flaking skin overlying inflammation on the knees, elbows, scalp or elsewhere.
Garlic’s anti-inflammatory constituents may soothe the inflammation.
Action: Do a patch test (see page 87).
Apply garlicky oil from a garlic oil-macerate (see page 37), or garlic oil (for example, from a garlic ‘perle’), to affected areas twice a day. Maximize the content of allicin derivatives in homemade garlic oil-macerate by standing the newly crushed garlic for 90 minutes before adding the oil.
Alternatively, bathe infected areas with garlic water (see page 41).
Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
This results from a fungal skin infection. There is good evidence that garlic and, in particular, ajoene, can help:
In a Venezuelan study, 60 soldiers with ringworm or ‘jock itch’ were treated with ajoene gel, or cream containing terbinafine (an anti-fungal drug), for 2 months. Healing occurred in 73 and 71 percent of the two groups respectively. The researchers concluded that ajoene is useful.
Arzneimittel-Forschung,1999
Action: Do a patch test (see page 87).
Since ajoene gel isn’t available commercially, apply garlic oil-macerate twice a day until 14 days after the skin has healed. Maximize the content of allicin derivatives in homemade garlic oil-macerate by leaving the newly crushed garlic to stand for 90 minutes before adding the oil.
Alternatively, bathe the infected area with garlic water (see page 41).
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Scientific evidence now backs up the belief that garlic increases libido and discourages impotence. For example, nitric oxide is now known to be vital for penile erection, and garlic increases nitric-oxide levels. Garlic also expands arteries, improving blood flow to the hormone-producing glands and the genitals. What’s more, garlic boosts testosterone, and garlic’s diallyl disulfide boosts luteinizing hormone (a pituitary hormone that regulates testosterone production).
Japanese researchers found that rats fed with garlic had higher testosterone and lower corticosterone after 28 days. Also, giving diallyl disulfide increased luteinizing hormone.
Journal of Nutrition, 2001
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Folk wisdom has it that applying garlic reduces the pain and itching of this varicella-zoster viral infection. After chickenpox (usually contracted many years before), these viruses lie dormant in the sensory nerve cells of a particular nerve until some kind of trigger reawakens them to cause shingles in the area supplied by that nerve.
Garlic inactivates the related viruses Herpes simplex 1 and 2. While I can find no mention of garlic acting against varicella-zoster viruses, it must be worth a try.
Action: Do a patch test (see page 87).
Apply garlic oil from a garlic perle, or the garlicky oil from a garlic oil-macerate (see page 37), twice a day. Maximize the content of allicin derivatives in homemade garlic oil-macerate by leaving the newly crushed garlic to stand for 90 minutes before adding the oil.
Alternatively, bathe the infected area with garlic water (see page 41).
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic is a useful treatment for bacterial, viral and fungal skin infections. In World War I, the British Government paid a shilling a pound for garlic to prevent wound infections.
Action: Do a patch test (see page 87).
Apply garlic oil from a garlic perle, or the oily part of a garlic oilmacerate (see page 37), twice a day. Maximize the content of allicin derivatives in homemade garlic oil-macerate by leaving the newly crushed garlic to stand for 90 minutes before adding the oil.
Alternatively, bathe the infected area with garlic water (see page 41).
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Most strokes (‘brain attacks’) are thrombotic (resulting from a clot in a brain artery); the rest are haemorrhagic (resulting from bleeding from a brain artery).
Strokes are encouraged by atherosclerosis (see ‘Artery disease’, page 92), chronic infection (see page 111), diabetes (see page 102), high blood pressure (see page 108), an increased tendency to inflammation (see page 112) or blood-clotting (see ‘Heart attacks’, page 106), and high cholesterol (see page 109). Garlic may help to prevent these.
Action: Include garlic in your daily diet or take a garlic supplement. You need water- and oil-soluble sulfur compounds (see page 85).
Garlic is a useful remedy for infection of the mouth or skin with the yeast-like fungus Candida albicans. Test-tube studies show garlic’s allicin is highly effective and ajoene inhibits the fungal growth.
Action: Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
If you have a mouth infection, chew then spit out a raw garlic clove several times a day, though stop if this causes irritation.
If you have a skin infection, first do a patch test (see page 87). If satisfactory, apply garlic oil (for example, from a garlic perle or garlic oil-macerate) several times a day.
Alternatively, bathe the infected area with garlic water (see page 31).
In the case of a vaginal infection, take garlic as above but do not be tempted to follow the sometimes-given advice to insert a raw garlic clove in the vagina because it could become stuck, in which case it could encourage other infection.
This results from bacterial decay exposing nerve endings in a tooth’s dentine. Garlic is a traditional remedy and its success may be because it kills infecting bacteria, or reduces inflammation.
Action: Apply crushed garlic that you have left to stand for 90 minutes, or garlic oil (for example, from a garlic perle or garlic oilmacerate – see page 37). Limit the first application to 10 minutes and stop if it irritates your gums. Repeat four times a day.
Alternatively, rinse your mouth with garlic water (see page 41) four times a day.
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).
Garlic’s anti-viral effects are a good enough reason to try it for warts and verrucas. Several studies now provide backing:
In a study of 28 people, warts vanished within 1–2 weeks in those who applied an oil-soluble garlic extract twice a day.
International Journal of Dermatology, 2005
In this study warts on the hands of five children were treated with garlic. Each night, a clove’s cut surface was rubbed over each wart, any stray juice cleaned from the surrounding area, and the wart covered overnight with a sticking plaster (adhesive bandage). All the warts disappeared within 7–12 weeks. The treatment was well tolerated apart from in one child, who had itching.
Pediatric Dermatology, 2002
Action: Do a patch test (see page 87).
Smear a little petroleum jelly (‘Vaseline’) on to the skin around the wart. Apply to the wart either crushed raw garlic that has been left to stand for 90 minutes, garlic oil from a garlic perle or the garlicky oil from a garlic oil-macerate (see page 37). Maximize the content of allicin derivatives in homemade garlic oil-macerate by standing the newly crushed garlic for 90 minutes before adding the oil. Cover with a large sticking plaster or piece of duct tape, and repeat each day until the wart goes (probably 7–10 days, though it may take several weeks to disappear).
Include garlic in your daily diet or take a garlic supplement. You need oil-soluble sulfur compounds (see page 85).