C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use;
F: Strong scientific evidence against this use.
High Cholesterol (Rate B). Multiple studies in humans have reported small reductions in total blood cholesterol and low-density lipoproteins ("bad cholesterol") over short periods of time (4 to 12 weeks). It is not clear if there are benefits after this amount of time. Effects on high-density lipoproteins ("good cholesterol") are not clear. This remains an area of controversy. Well-designed and longer studies are needed in this area.
Anti-fungal, applied to the skin (Rate C). Several studies describe the application of garlic to the skin to treat fungal infections, including yeast infections. Garlic can cause severe burns and rash when applied to the skin of sensitive individuals.
Anti-platelet effects, blood thinning (Rate C). Garlic has been associated with several cases of bleeding, therapy should be applied with caution (particularly in patients using other agents that may precipitate bleeding).
Atherosclerosis, hardening" of the arteries (Rate C). Preliminary research in humans suggests that deposits of cholesterol in blood vessels may not grow as quickly in people who take garlic. It is not clear if this is due to the ability of garlic to lower cholesterol levels, or to other effects of garlic.
Cancer (Rate C). Preliminary human studies suggest that regular consumption of garlic (particularly unprocessed garlic) may reduce the risk of developing several types of cancer including gastric and colorectal malignancies. Some studies use multi-ingredient products so it is difficult to determine if garlic alone may play a beneficial role. Further, well designed human clinical trials are needed to conclude whether eating garlic or taking garlic supplements may prevent or treat cancer.
High blood pressure (Rate C). Numerous human studies report that garlic can lower blood pressure by a small amount, but larger, well-designed studies are needed to confirm this possible effect.
Tick repellant (Rate C). In early study, self-reports of tick bites were significantly less in people receiving garlic over a placebo "sugar" pill. Further, a well-designed study is needed to confirm these results.
Upper respiratory tract infection (Rate C). Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. However, this has not been demonstrated in well-designed human studies.
Diabetes (Rate D). Animal studies suggest that garlic may lower blood sugar and increase the release of insulin, but studies in humans do not confirm this effect.
when you can grow garlic in your garden.