Garlic and Immune Function
This blog has not been approved by your local health department and is not intended to provide diagnosis, treatment, or medical advice.
In this article:
- What are the scientifically confirmed effects of garlic?
- Do “odor controlled” or “odorless” garlic products contain allicin?
- Can garlic help lower blood pressure and cholesterol levels?
- What about aged garlic?
- What brand do you recommend?
- How much garlic do I need?
- Is garlic safe?
- What about antimicrobial and immune-enhancing effects?
- Does garlic interact with any drugs?
Garlic has been used throughout history virtually all over the world as a medicine. Its use predates written history. Sanskrit records document the use of garlic remedies to approximately 5,000 years ago, while the Chinese have been using it for at least 3,000 years.The Codex Ebers, an Egyptian medical papyrus dating to about 1,550 B.C., mentions garlic as an effective remedy for a variety of ailments, including high blood pressure, headache, bites, worms, and tumors. Hippocrates, Aristotle and Pliny cited numerous therapeutic uses for garlic. Stories, verse, and folklore (such as its alleged ability to ward off vampires) also give historical documentation to the healing power of garlic. Sir John Harrington in The Englishman’s Doctor, written in 1609, summarized garlic’s virtues and faults:
Garlic then have power to save from death
Bear with it though it maketh unsavory breath,
And scorn not garlic like some that think
It only maketh men wink and drink and stink.
Another favorite saying about garlic is “Eat garlic and gain your health, but lose your friends.” Fortunately, there are now commercial preparations that provide all of the health benefits of garlic without the social consequences.
Garlic has a wide range of well-documented effects including helping to fight infection and boosting immune function; preventing cancer, and the cardiovascular benefits of lowering cholesterol and blood pressure. All of these beneficial effects of garlic are attributed to its sulfur-containing compounds: allicin, diallyl disulfide, diallyl trisulfide, and others. Allicin is mainly responsible for the pungent odor of garlic. It is formed by the action of the enzyme alliinase on the compound alliin. The enzyme is activated by heat, oxygen, or water. This accounts for the fact that cooked garlic, as well as “aged garlic preparations,” and garlic oil products produce neither as strong an odor as raw garlic nor nearly as powerful medicinal effects.
Some do and some do not. Since allicin is the component in garlic that is responsible for its easily identifiable odor, some manufacturers have developed highly sophisticated methods in an effort to provide the full benefits of garlic – they provide “odorless” garlic products concentrated for alliin because alliin is relatively “odorless” until it is converted to allicin in the body. Products concentrated for alliin and other sulfur components provide all of the benefits of fresh garlic if they are manufactured properly, but are more “socially acceptable.” Because alliin and alliinase are very stable when garlic is properly processed, there is a method to ensure that the allicin is not produced until the garlic powder mixes with the fluids of the intestinal tract. This method is referred to as “enteric-coating.” This method coats the specially prepared garlic in such a manner so that the tablet does not break down until after it has passed through the stomach. If a non-enteric coated garlic preparation is used, the stomach acid will destroy the majority of the formed allicin. So, these preparations are not likely to produce as good of results as a high quality, enteric-coated product. The same can be said for aged garlic and garlic oil products as these forms of garlic contain absolutely no allicin or allicin degradation products.
Dr. Lawson discovered that there were basically two major problems. First of all, many of the garlic products contained little allinase activity. There was plenty of alliin, but since the activity of allinase was low, the level of allicin formed was also low. Next, Dr. Lawson found that many of the tablets contained excipients (e.g., binders and fillers) that actually inhibit allinase activity. The allinase activity in 63% of the brands was less than 10% of expected activity. The inability to release an effective dose of allicin would explain why so many of the studies with garlic supplements fail to show benefit in lowering cholesterol or blood pressure.
For example, studies done with one particular garlic supplement prior to 1993 were mostly positive. In fact, the results from these positive studies were the main reason garlic supplements have been allowed in Germany and in the U.S. to refer to cholesterol-lowering activity. However, studies published since 1995 have failed to show a consistent effect in lowering cholesterol.
While the authors of the negative studies on garlic have felt that the underlying reason for the results was a better-designed study, a more likely explanation is that they are due to a poorer quality tablet. Specifically, research conducted by Dr. Lawson has shown that tablets manufactured before 1993 were twice as resistant to disintegration in acid as tablets manufactured after 1993 and that the older tablets released three times the amount of allicin than the more recently manufactured tablets.
Examination of the package labels shows several changes in tablet excipients between the pre- and post-1993 tablets. Again, these excipients are believed to block allinase activity.
Yes, but there are some important caveats as mentioned above. The studies showing a positive effect of garlic and garlic preparations are those that deliver a sufficient dosage of allicin. The negative studies do not. In the positive double-blind studies in patients with initial cholesterol levels greater than 200 mg/dl, supplementation with garlic preparations providing a daily dose of at least 10 mg allicin or a total allicin potential of 4,000 mcg total serum cholesterol levels dropped by about 10% to 12%, LDL cholesterol decreased by about 15%, HDL cholesterol levels usually increased by about 10%, and triglyceride levels dropped by 15%.4-9 Blood pressure readings also dropped with typical reductions of 11 mm Hg for the systolic and 5.0 in the diastolic within a one to three month period.
Since aged garlic does not contain allicin, it does not produce any significant benefits on either blood pressure or cholesterol levels. It may provide some other benefits on the cardiovascular system, but the significance of these effects has not been fully evaluated.
Based upon Dr. Lawson’s new research, as well as the research conducted by Natural Factors, I am now endorsing Garlic Factors. I feel that it gives a person the best chance of getting all the benefits of fresh garlic minus the odor.
Based on the results of the positive clinical trials, the dosage of a commercial garlic product should provide a daily dose of at least 10 mg alliin or a total allicin potential of 4,000 mcg. This dosage equates to roughly one to four cloves of fresh garlic. Each tablet of Garlic Factors provides 6,150 mcg of allicin, very high potency. But, the real advantage of Garlic Factors is the fact that it is manufactured by Natural Factors — the experts in effective natural products. As a result, you are assured that Garlic Factors has been designed to produce results consistently.
Garlic preparations taken orally, even “odorless” products, can produce a garlic odor on the breath and through the skin. Gastrointestinal irritation and nausea are the most frequent side effects. Beware of the propaganda on the dangers of allicin. I do not argue that acute and prolonged feeding of large amounts of raw garlic to rats results in anemia, weight loss and failure to grow, and even death. However, the dosages of fresh garlic used in these studies to produce these toxic effects were incredibly high, e.g., 500 mg of fresh garlic per 100 g of body weight.
Garlic does exert antibacterial, antiviral, and anti-fungal activity. However, it may also work against some intestinal parasites. Garlic’s antibiotic activity is only roughly 1% the strength of penicillin, so it is certainly not a substitute for antibiotics. It is especially supportive against the overgrowth of the yeast candida albicans. Garlic appears to exert many positive effects on the immune system and human population studies have shown that eating garlic regularly reduces the risk of many cancers. This is partly due to garlic’s ability to reduce the formation of carcinogenic compounds as well as its positive effects on the immune system.
Theoretically, garlic preparations may potentiate the effects of the blood-thinning drug Coumadin® (warfarin) as well as enhance the antiplatelet effects of drugs like aspirin and Ticlid® (ticlopidine). If you are taking these drugs, please consult a physician before taking a garlic product.
Garlic may increase the effectiveness of drugs that lower blood sugar levels in the treatment of non-insulin dependent diabetes (Type 2 diabetes) such as glyburide (Diabeta, Micronase). Consult a physician to discuss proper monitoring of blood sugar levels before taking a garlic product.
- Koch H and Lawson L (eds.): Garlic: The Science and Therapeutic Application of Allium Sativum L and Related Species, 2nd Edition.Williams & Wilkins, Baltimore, MD, 1996.
- Lawson LD and Wang ZJ.Tablet quality: A major problem in clinical trials with garlic supplements. Forsch Kmplmentaermed 7:45, 2000.
- Lawson LD,Wang ZJ and Papdimitrou D. Allicin release under simulated gastrointestinal conditions from garlic powder tablets employed in clinical trials on serum cholesterol. Planta Medica 2001;67:13-18.
- Stevinson C, Pittler MH and Erst E. Garlic for treating hypercholesterolemia: A meta-analysis of randomized clinical trials. Ann Intern Med 133:420-9, 2000.
- Kleijnen J, et al.: Garlic, onions and cardiovascular risk factors: A review of the evidence from human experiments with emphasis on commercially available preparations. Br J Clin Pharmacol 28:535-44, 1989.
- Warshafsky S, Kamer RS and Sivak SL: Effect of garlic on total serum cholesterol. Ann Intern Med 119:599-605, 1993.
- Jain AK, et al.: Can garlic reduce levels of serum lipids? A controlled clinical study. Am J Med 94:632-5, 1993.
- Rotzch W, et al.: Postprandial lipaemia under treatment with Allium sativum. Controlled double-blind study in healthy volunteers with reduced HDL2-cholesterol levels. Arzneim Forsch 42:1223-7, 1992.
- Mader FH:Treatment of hyperlipidemia with garlic-powder tablets. Arzneim Forsch 40:1111-6, 1990.
- Silagy CA and Neil HA: A meta-analysis of the effect of garlic on blood pressure. J Hypertens 12:463-8, 1994.
- Reuter HD: Allium sativum and Allium ursinum: Part 2. Pharmacology and medicinal application. Phytomed 2:73-91, 1995.
- Steiner M, et al.: A double-blind crossover study in moderately hypercholesterolemic men that compared the effect of aged garlic extract and placebo administration on blood lipids. Am J Clin Nutr 64:866-70, 1996.
- Nakagawa S, et al.: Effect of raw and extracted-aged garlic juice on growth of young rats and their organs after perioral administration. J Toxicol Sci 5:91-112, 1980.
- Joseph PK, Rao KR and Sundaresh CS.Toxic effects of garlic extract and garlic oil in rats. Indian J Exp Biol 27:977-9, 1989.