Diet & Fitness

 

Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial.¹⁵ The preparation used, standardized for 0.6% allicin content, provided 900 mg of garlic powder per day. The people in this trial were 50 to 80 years old, and the benefits were most notable in women. This trial points to the long-term benefits of garlic to both prevent and possibly slow the progression of atherosclerosis in people at risk.

Garlic has also lowered cholesterol levels in double-blind research,¹⁶ though more recently, some double-blind trials have not found garlic to be effective.^17,18,19 Some of the negative trials have flaws in their design.²⁰ Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear.²¹

Garlic has also been shown to prevent excessive platelet adhesion (stickiness) in humans.²² Allicin, often considered the main active component of garlic, is not alone in this action. The constituent known as ajoene has also shown beneficial effects on platelets.²³ Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans,²⁴ an event believed to be a significant factor in the development of atherosclerosis.

Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind²⁵ and other controlled²⁶ trials to decrease the overactive coagulation of blood that may contribute to atherosclerosis.

Numerous medicinal plants and plant compounds have demonstrated an ability to protect LDL cholesterol from being damaged by free radicals. Garlic,²⁷ ginkgo,²⁸ and guggul²⁹ are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans.

Garlic supplements, in doses ranging from 600–1,200 mg per day, have consistently been shown in randomized controlled trials to lower high blood pressure to a degree that is comparable to anti-hypertensive medications.^30,31,32 One randomized controlled trial that included 88 participants with high blood pressure found treatment with 1,200 mg of aged garlic extract daily for 12 weeks reduced systolic blood pressure by an average of 5 mmHg. The trial identified a subgroup of 29 responders to garlic therapy whose blood pressure dropped by more than 3%; in this subgroup, systolic blood pressure was reduced by an average of 11.5 mmHg and diastolic blood pressure by 6.3 mmHg.³³ Another trial found garlic extract lowered blood pressure in hypertensive patients with severe coronary artery disease: the trial included 56 participants with severe coronary artery disease who were given 800 mg of garlic extract per day or placebo for three months. Although the effect of garlic on blood pressure was not significant overall, in the 18 participants with baseline hypertension, garlic lowered blood pressure significantly more than placebo.³⁴ Furthermore, garlic extract has been found to reduce arterial stiffness, improve blood glucose control, lower high cholesterol levels, decrease blood clot risk, and improve gut microbial balance, and may reduce the risks of heart attack and stroke.^33,36

Fresh garlic may also help lower high blood pressure: In an open trial, 40 participants with metabolic syndrome were given raw crushed garlic in an amount based on body weight (100 mg per kg body weight twice daily). After four weeks, blood pressures were reduced, and other markers of metabolic health, including waist circumference, triglyceride levels, fasting glucose levels, and cholesterol levels were improved.³⁷ A six-year observational study found those who eat the largest amount of allium vegetables such as garlic and onion were less likely to develop high blood pressure, chronic kidney disease, and cardiovascular events.³⁸

Numerous randomized controlled trials and meta-analyses have found garlic can reduce total and LDL-cholesterol levels and raise HDL-cholesterol levels.³⁸ A meta-analysis of 14 randomized controlled trials noted garlic had positive effects on all types of cholesterol levels.³⁹ Similarly, a meta-analysis that included data from 29 randomized controlled trials with a total of almost 2,300 participants found treatment with garlic for two months or longer reduced total cholesterol by 8% and LDL-cholesterol by 10%, although HDL-cholesterol levels were only slightly improved.⁴⁰ One meta-analysis concluded garlic improved lipid profiles in people with type 2 diabetes after pooling findings from 39 randomized controlled trials.⁴¹ The majority of clinical trials in these meta-analyses used garlic powder at doses of 300–900 mg per day, but some used garlic oil, aged garlic extract, or raw garlic. In addition to inhibiting cholesterol synthesis in the liver, garlic has been found to reduce oxidation of LDL-cholesterol, lower blood pressure, and decrease the risk of blood clots, lowering the risks of atherosclerosis and cardiovascular events.⁴²

 

Reports on many clinical trials of garlic performed until 1998 suggested that triglycerides were lowered by an average of 8–27% and cholesterol by 9–12% over a one- to four-month period.^43,44,45 Most of these trials used 600–900 mg per day of a garlic supplement standardized to alliin content and allicin potential. More recently, however, three double-blind clinical trials have found garlic to have minimal success in lowering triglycerides and cholesterol.^46,47,48 One negative trial has been criticized for using a steam distilled garlic “oil” that has no track record for this purpose,⁴⁹ while the others used the same standardized garlic products as the previous positive clinical trials. Based on these findings, the use of garlic should not be considered a primary approach to lowering high triglycerides and cholesterol.⁵⁰

Odor-controlled, enteric-coated garlic tablets standardized for allicin content can be taken in the amount of 900 mg daily (providing 5,000–6,000 mcg of allicin), divided into two or three daily portions.

 

A standardized extract of garlic has been tested as a treatment for intermittent claudication. In a double-blind trial, the increase in walking distance was significantly greater in people receiving garlic powder extract (400 mg twice per day for 12 weeks) than in those given a placebo.⁵¹

In a double-blind trial, participants took one capsule per day of a placebo or a garlic supplement that contained stabilized allicin (the amount of garlic per capsule was not specified) for 12 weeks between November and February. During that time, the garlic group had 63% fewer colds and 70% fewer days ill than did the placebo group.⁵² In another double-blind study of healthy volunteers, supplementing with 2.6 grams per day of an aged-garlic extract for 90 days decreased by 58% the number of days on which severe cold or influenza symptoms occurred.⁵³

In a double-blind study of healthy volunteers, supplementing with 2.6 grams per day of an aged-garlic extract for 90 days decreased by 58% the number of days on which severe cold or influenza symptoms occurred.⁵⁴

 

Herbs that directly attack microbes include the following: chaparral, eucalyptus, garlic, green tea, lemon balm (antiviral), lomatium, myrrh, olive leaf, onion, oregano, pau d’arco (antifungal), rosemary, sage, sandalwood, St. John’s wort, tea tree oil, thyme, and usnea.

Garlic has been demonstrated to kill parasites, including amoeba⁵⁵ and hookworm,⁵⁶ in test tubes and in animals. Older studies in humans support the use of garlic to treat roundworm, pinworm, and hookworm.⁵⁷ However, due to a lack of clinical trials, the amount of garlic needed to treat intestinal parasites in humans is not known.

 

Garlic may assist in combating opportunistic infections. In one trial, administration of an aged garlic extract reduced the number of infections and relieved diarrhea in a group of patients with AIDS.⁵⁸ Garlic’s active constituents have also been shown to kill HIV in the test tube, though these results have not been confirmed in human trials.⁵⁹

 

In a preliminary trial, topical application of garlic cloves was used successfully to treat warts in a group of children. A clove was cut in half each night and the flat edge of the clove was rubbed onto each of the warts, carefully cleaning the surrounding areas, so as not to spread any garlic juice. The areas were covered overnight with Band-Aids or waterproof tape and were washed in the morning. In all cases, the warts cleared completely after an average of nine weeks.⁶⁰ In another study, 23 people with warts applied an oil-soluble garlic extract twice a day to the warts. Complete recovery was seen in every case after one to two weeks. A water-soluble garlic extract was less effective.⁶¹ Side effects after application of the oil-soluble extract included blistering, redness, burning, and increased pigmentation of the skin around the application area, which usually disappeared completely in one to two weeks. Zinc oxide ointment was applied to the surrounding normal skin in all cases in an attempt to prevent these side effects.

 

The compound known as ajoene, found in garlic, is an antifungal agent. In a group of 34 people using a 0.4% ajoene cream applied once per day, 79% of them saw complete clearing of athlete’s foot after one week; the rest saw complete clearing within two weeks.⁶² All participants remained cured three months later. One trial found a 1% ajoene cream to be more effective than the standard topical drug terbinafine for treating athlete’s foot.⁶³ Ajoene cream is not yet available commercially, but topical application of crushed, raw garlic may be a potential alternative application.

 

In many parts of Europe, herbal supplements are considered standard medical treatment for BPH. Although herbs for BPH are available without prescription, men wishing to take them should be monitored by a physician.

In a preliminary study, supplementation with a special aged garlic extract (Kastamonu Garlic) in the amount of 1 ml per 2.2 pounds of body weight per day for one month resulted in a 32% reduction in the size of the prostate gland and a significant improvement in urinary symptoms.⁶⁴ It is not known whether other forms of garlic would have the same effect.

 

Garlic has been reported to have anti-Helicobacter activity in test-tube studies.^65,66 In a preliminary trial, garlic supplementation (300 mg in tablets three times daily for eight weeks) failed to eradicate H. pylori in participants with active infections.⁶⁷ In another preliminary trial, participants with active H. pylori infections added 10 sliced cloves of garlic to a meal.⁶⁸ The addition of garlic failed to inhibit the growth of the organism. Further trials using garlic extracts are needed to validate the anti-Helicobacter activity of garlic observed in test tubes. Until then, evidence to support the use of garlic for H. pylori-related peptic ulcers remains weak.

 

Ear drops with mullein, St. John’s wort, and garlic in an oil or glycerin base are traditional remedies used to alleviate symptoms, particularly pain, during acute ear infections. No clinical trials have investigated the effects of these herbs in people with ear infections. Moreover, oil preparations may obscure a physician’s view of the ear drum and should only be used with a healthcare professional’s directions.

 

Ear drops with mullein, St. John’s wort, and garlic in an oil or glycerin base are traditional remedies used to alleviate symptoms, particularly pain, during acute ear infections. No clinical trials have investigated the effects of these herbs in people with ear infections. Moreover, oil preparations may obscure a physician’s view of the ear drum and should only be used with a healthcare professional’s directions.

 

Numerous herbs are used traditionally around the world to promote production of breast milk.⁶⁹ Herbs that promote milk production and flow are known as galactagogues. Stinging nettle (Urtica dioica) enriches and increases the flow of breast milk and restores the mother’s energy following childbirth.⁷⁰Vitex (Vitex agnus castus) is one of the best-recognized herbs in Europe for promoting lactation. An older German clinical trial found that 15 drops of a vitex tincture three times per day could increase the amount of milk produced by mothers with or without pregnancy complications compared with mothers given vitamin B1 or nothing. Vitex should not be taken during pregnancy.⁷¹ Goat’s rue (Galega officinalis) also has a history of use in Europe for supporting breast-feeding. Taking 1 teaspoon of goat’s rue tincture three times per day is considered by European practitioners to be helpful in increasing milk volume.⁷² Studies are as yet lacking to support the use of goat’s rue as a galactagogue. In two preliminary trials, infants have been shown to nurse longer when their mothers ate garlic than when their mothers took placebos.^73,74 However, some infants may develop colic if they consume garlic in breast milk.

 

Garlic has demonstrated significant antifungal activity against C. albicans in both animal and test tube studies.^75,76,77 Greater anti-Candida activity has resulted from exposing Candida to garlic, than to nystatin—the most common prescription drug used to fight Candida.⁷⁸ No clinical studies of garlic in the treatment of candidiasis have yet been conducted. However, some doctors suggest an intake equal to approximately one clove (4 grams) of fresh garlic per day; this would equal consumption of a garlic tablet that provides a total allicin potential of 4,000 to 5,000 mcg.

 

Garlic has demonstrated significant antifungal activity against C. albicans in both animal and test tube studies.^79,80,81 Greater anti-Candida activity has resulted from exposing Candida to garlic, than to nystatin—the most common prescription drug used to fight Candida.⁸² No clinical studies of garlic in the treatment of candidiasis have yet been conducted. However, some doctors suggest an intake equal to approximately one clove (4 grams) of fresh garlic per day; this would equal consumption of a garlic tablet that provides a total allicin potential of 4,000 to 5,000 mcg.