Several garlic-derived chemicals can help slow blood clotting by keeping blood platelets from clumping together. In addition, garlic helps break up or prevent blood clots. Since many heart attacks and strokes are believed to be caused by spontaneous clots in blood vessels, these anticoagulant actions may be very helpful in stroke and heart attack prevention. Test tube research has established that garlic extracts are active against a range of disease-causing bacteria, including staphylococcus aureus and streptococcus pneumoniae. It is only about one percent as active as penicillin, however.
Garlic extract can also fight helicobacter pylori, a bacterium that causes stomach ulcers.
Animal research has demonstrated that garlic has the potential to improve resistance to tumors. Other tests conducted on rats and dogs have also shown that garlic can return irregular heart rhythms back to normal. One of the most intriguing possibilities for garlic is that regular consumption may help prevent cancer. Other studies have indicated that people who eat garlic more often seem less susceptible to colon cancer. The National Academy of Sciences has yet to specify a recommended daily allowance for garlic.