An in vitro test has shown that allicin reacts with blood and oxidizes it: All allicin disappeared within a few minutes after being mixed with blood (1). At the same time, the color of the blood changed from red to black (Figure 1). This finding showed that allicin oxidized the red pigment hemoglobin in the red blood cells to methemoglobin, which irreversibly cannot carry oxygen to the organs/tissues (Figure 2). Cases of anemia have been seen from excessive consumption of some raw garlic preparations containing allicin and its degraded compounds (2,3). Therefore, such preparations should be used in moderation and with caution. Since most nutrients/substances taken orally and absorbed by the intestine must first go through the liver, allicin reactivity in the liver has also been studied (4). Small amounts of allicin could be detected in the effluent (fluids surrounding the cells) only when allicin was injected into the liver tissue at a high concentration, which caused severe liver cell damage. At lower dosages, which did not cause cell injury, allicin could not be detected in the effluent. In another study, allicin disappeared very rapidly when incubated with liver tissue (5).
Furthermore, it has been shown that after ingestion of 25 g of raw garlic containing a significant amount of allicin, neither allicin nor sixteen of its common transformation products were detected in either the serum or urine from 1 to 24 hours after ingestion (6).
These data suggest that allicin taken orally may not be delivered to the organs and tissues, and that it does not appear to be a biologically beneficial compound in garlic.
Fig. 1 The color of red blood cells changes to black when mixed with allicin (right test tube). Physiological saline as a control was added to the left test tube.
Fig. 2 The red line shows the spectrophotometry profile of hemoglobin prepared from the control blood. The brown line shows the formation of methemoglobin when blood was mixed with allicin. (The appearance of the third peak is characteristic of methemoglobin).
Allicin: Not Found in Top Garlic Products.
For years, allicin has been deemed as the compound responsible for the benefits of garlic. It has shown an ability to kill bacteria and fungus in test tubes and topically crushed raw garlic has been used in wars to fight infections. However, no clinical trials have been performed with allicin and it has not become a commercial product, mainly because of its chemical instability but also because of its pungent odor and irritating nature. Research has shown that garlic supplements actually contain no allicin (allicin is a odorous and transient garlic compound). Contrary to the popular myth that a garlic product must contain allicin to be beneficial, allicin has not been conclusively proven to be responsible for garlic’s known health benefits. Most of the garlic or garlic products that have been used to to demonstrate garlic’s health effects do not contain significant amounts of allicin.
Equally untrue is the myth that if garlic or a garlic product does not have a garlic odor then it does not provide benefits. A major part of the data on the benefits of garlic is derived from studies of cooked garlic, pickled garlic, aged garlic, and Aged Garlic Extract. All of these forms of garlic have little typical garlic odor.
Intestinal Conditions Hinder the Generation of Allicin.
Allicin production in the body (from naturally occurring alliin and alliinase in garlic) is inhibited by various body fluids. Most supplements can only produce allicin in water but not in the body. Stomach fluids have been shown to destroy the enzyme, alliinase, in raw garlic powders which is necessary to generate allicin.
What About Enteric Coatings?
Enteric-coated supplements can potentially produce allicin in the intestinal tract, but….
— much of the allicin production is inhibited by intestinal fluids (only 60% of the amount produced in water can be produced in intestinal fluids).
— the remaining allicin may destroy not only bad, but also good bacteria. Allicin is a harsh oxidizing agent and high amounts have been shown to aggravate the intestinal lining as well as the stomach.
— if the allicin is absorbed by the liver in small amounts, it is completely metabolized or detoxified; however, if absorbed in large amounts, it may damage liver tissue.
— if allicin makes it past the liver to the blood, it may oxidize red blood cells.
Allicin Is Not Bioavailable.
No allicin found in the body following oral intake. Allicin is not biologically active inside of the body Allicin has not been conclusively proven to be responsible for garlic’s known health benefits. Allicin was not found in the blood or urine after consumption of approximately 90,000 mcg (roughly 10 cloves). It is lost en route and therefore is unlikely to be the active compound in garlic.
A study in which participants consumed a large amount of allicin (approximately 90,000mcg) via crushed raw garlic (25 grams; roughly 10 cloves) revealed that neither allicin nor 16 of its daughter compounds could be detected in blood or urine from one to twenty-four hours after consumption. Due to its high reactivity, allicin was shown to be completely metabolized in the liver. If allicin could even make it to the blood where it could be delivered throughout the body, studies have shown that it changes into other compounds within five minutes and may oxidize the blood cells, in the process, causing them to lose their ability to carry oxygen.
“Allicin is not biologically active inside of the body”
Yukihiro Kodera, at the Designer Foods III Symposium: Research Update on Phytochemicals in Garlic, Soy and Licorice held in May, 1994 in Washington, D.C. found the following:
“Under simulated digestive conditions, little allicin was released from a garlic powder which contained both alliin and alliinase. When allicin was mixed with blood, it disappeared very rapidly, and the formation of trace amounts of allylmercaptan and diallyl disulfide were observed. Allicin also converted the hemoglobin in red blood cells to methemoglobin. Furthermore, allicin has been shown to disappear upon contact with the liver; no allicin could be detected in the effluent when allicin was perfused into an isolated liver.”
“Though allicin was considered to be a key compound in garlic in the past, recent scientific findings, including the pharmacokinetics and metabolism of organosulfur compounds in garlic, have revealed that allicin is not biologically active inside of the body…”
Allicin has not been conclusively proven to be responsible for garlic’s known health benefits.
Following are some conclusions drawn about allicin from garlic scientists at the “First World Congress on the Health Significance of Garlic and Garlic Constituents” held in August 1990 in Washington, D.C.:
Contrary to the popular myth that a garlic product must contain allicin to be beneficial, allicin has not been conclusively proven to be responsible for garlic’s known health benefits. Most of the garlic or garlic products that have been based to demonstrate garlic health effects do not contain significant amounts of allicin. (Allicin is an odorous and transient garlic compound.)
Equally untrue is the myth that if garlic or a garlic product does not have a garlic odor it does not provide benefits. A major part of the data on the benefits of garlic is derived from studies of cooked garlic, pickled garlic, aged garlic, and Aged Garlic Extract™. All of them have little typical garlic odor.
Other Compounds Must Be Responsible for the Benefits of Garlic
Various forms of garlic, which contain no allicin (e.g., cooked, steamed, pickled, and aged garlic extract), have demonstrated an array of benefits in studies. Therefore, it is logical that compounds other than allicin are responsible for such benefits. To date, well over 100 compounds have been identified in garlic preparations. Presently, S-allyl cysteine appears to be a very promising compound with good absorption. Again, according the research of Kodera et al:
“The pharmacokinetic studies of S-allyl cysteine demonstrated rapid absorption and almost 100% bioavailability after oral administration. In addition, since both the safety and effectiveness of S-allyl cysteine have been reported, this compound appears to play an important role in garlic’s medicinal effects.”
Though individual compounds, such as S-allyl cysteine, have shown activity in studies and are absorbed by the body, it is likely that a synergism of various compounds provide the benefits of garlic. This is in agreement with Dr. Koch, a renowned Austrian scientist who stated that the activity of various sulfur compounds could not alone be responsible for the benefits of garlic and fixation on a single group of components can lead to mistakes and wrong conclusions.