1. Allicin is a Highly Reactive Compound

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).