Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial.¹ The preparation used, standardized for 0.6% allicin content, provided 900 mg of garlic powder per day. The people in this trial were 50 to 80 years old, and the benefits were most notable in women. This trial points to the long-term benefits of garlic to both prevent and possibly slow the progression of atherosclerosis in people at risk.

Garlic has also lowered cholesterol levels in double-blind research,² though more recently, some double-blind trials have not found garlic to be effective.^3,4,5 Some of the negative trials have flaws in their design.⁶ Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear.⁷

Garlic has also been shown to prevent excessive platelet adhesion (stickiness) in humans.⁸ Allicin, often considered the main active component of garlic, is not alone in this action. The constituent known as ajoene has also shown beneficial effects on platelets.⁹ Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans,¹⁰ an event believed to be a significant factor in the development of atherosclerosis.

Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind¹¹ and other controlled¹² trials to decrease the overactive coagulation of blood that may contribute to atherosclerosis.

Numerous medicinal plants and plant compounds have demonstrated an ability to protect LDL cholesterol from being damaged by free radicals. Garlic,¹³ ginkgo,¹⁴ and guggul¹⁵ are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans.

A diet high in omega-6 fatty acids, found in certain vegetable oils such as corn, safflower, grapeseed, and sunflower oil, and in other foods such as nuts and seeds, appears to protect against atherosclerosis. Higher dietary intake or high body levels of omega-6 fatty acids has been associated with reduced coronary heart disease risk in numerous preliminary studies,¹⁶ and an analysis of several controlled trials found that replacing saturated fats in the diet with omega-6 fats reduces the risk of coronary heart disease by an average of 24%.¹⁷