Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial.²⁰ 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,²¹ though more recently, some double-blind trials have not found garlic to be effective.^{22 , 23 , 24} Some of the negative trials have flaws in their design.²⁵ Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear.²⁶

Garlic has also been shown to prevent excessive platelet adhesion (stickiness) in humans.²⁷ 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.²⁸ Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans,²⁹ 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-blind³⁰ and other controlled³¹ 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,³² ginkgo,³³ and guggul³⁴ are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans.

Supplementation with fish oil, rich in omega-3 fatty acids, has been associated with favorable changes in various risk factors for atherosclerosis and heart disease in some,^{37 , 38 , 39 , 40 , 41 , 42} but not all, studies.^{43 , 44 , 45} A double-blind trial showed that people with atherosclerosis who took fish oil (6 grams per day for 3 months and then 3 grams a day for 21 months) had significant slowing of progression of atherosclerotic plaques and a decrease in cardiovascular events (for example, heart attack and stroke) compared with those who did not take fish oil.⁴⁶ These results contradict the findings of an earlier controlled trial in which fish oil supplementation for two years (6 grams per day) did not promote major favorable changes in the diameter of atherosclerotic coronary arteries.⁴⁷

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research,^{48 , 49} though uncertainty remains about whether elevated homocysteine actually causes heart disease.^{50 , 51} Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes,⁵² evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, vitamin B12, and folic acid are associated with low levels of homocysteine⁵³ and supplementing with these vitamins lowers homocysteine levels.^{54 , 55}

While several trials have consistently shown that B6, B12, and folic acid lower homocysteine, the amounts used vary from study to study. Many doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid. Even researchers finding only inconsistent links between homocysteine and heart disease have acknowledged that a B vitamin might offer protection against heart disease independent of the homocysteine-lowering effect.⁵⁶ In one trial, people with normal homocysteine levels had demonstrable reversal of atherosclerosis when supplementing B vitamins (2.5 mg folic acid, 25 mg vitamin B6, and 250 mcg of vitamin B12 per day).⁵⁷ Similar results were seen in another study.⁵⁸

For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective.⁵⁹ Of these four supplements, folic acid appears to be the most important.⁶⁰ Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.⁶¹

Horny goat weed has historically been used in people with symptoms caused by hardening of the arteries, in particular those recovering from strokes. One study of older people who had symptoms due to hardening neck arteries found that a formula in which the main ingredient was horny goat weed was superior to one not containing horny goat weed at relieving symptoms and improving the electrocardiogram findings.⁶²

In some studies, people who consumed more selenium in their diet had a lower risk of heart disease.^{64 , 65} In one double-blind report, people who had already had one heart attack were given 100 mcg of selenium per day or placebo for six months.⁶⁶ At the end of the trial, there were four deaths from heart disease in the placebo group but none in the selenium group; however, the number of people was too small for this difference to be statistically significant. Some doctors recommend that people with atherosclerosis supplement with 100–200 mcg of selenium per day.

Tocotrienols may offer protection against atherosclerosis by preventing oxidative damage to LDL cholesterol.⁶⁷ In a double-blind trial in people with severe atherosclerosis of the carotid artery—the main artery supplying blood to the head—tocotrienol administration (200 mg per day) reduced the level of lipid peroxides in the blood. Moreover, people receiving tocotrienols for 12 months had significantly more protection against atherosclerosis progression, and in some cases reductions in the size of their atherosclerotic plaques, compared with those taking a placebo.⁶⁸

Experimentally increasing homocysteine levels in humans has led to temporary dysfunction of the cells lining blood vessels. Researchers are concerned this dysfunction may be linked to atherosclerosis and heart disease. Vitamin C has been reported in one controlled study to reverse the dysfunction caused by increases in homocysteine.⁶⁹ Vitamin C also protects LDL.⁷⁰

Despite the protective mechanisms attributed to vitamin C, some research has been unable to link vitamin C intake to protection against heart disease. These negative trials have mostly been conducted using people who consume 90 mg of vitamin C per day or more—a level beyond which further protection of LDL may not occur. Studies of people who eat foods containing lower amounts of vitamin C have been able to show a link between dietary vitamin C and protection from heart disease. Therefore, leading vitamin C researchers have begun to suggest that vitamin C may be important in preventing heart disease, but only up to 100–200 mg of intake per day.⁷¹ In a double-blind trial,⁷² supplementation with 250 mg of timed-release vitamin C twice daily for three years resulted in a 15% reduction in the progression of atherosclerosis, compared with placebo. Many doctors suggest that people take vitamin C—often 1 gram per day—despite the fact that research does not yet support levels higher than 500 mg per day.

In a double-blind trial, supplementing with vitamin K1 for three years appeared to slow the rate of progression of coronary artery calcification in elderly people who had preexisting coronary artery calcification. Participants in that study were randomly assigned to receive a multivitamin that contained 500 mcg per day of vitamin K1 or the same multivitamin without vitamin K1.⁷³ 

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research,^{74 , 75} though uncertainty remains about whether elevated homocysteine actually causes heart disease.^{76 , 77} Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes,⁷⁸ evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, vitamin B12, and folic acid are associated with low levels of homocysteine⁷⁹ and supplementing with these vitamins lowers homocysteine levels.^{80 , 81}

For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective.⁸² Of these four supplements, folic acid appears to be the most important.⁸³ Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.⁸⁴

Turmeric’s active compound curcumin has shown potent anti-platelet activity in animal studies.⁸⁵ It has also demonstrated this effect in preliminary human studies.⁸⁶ In a similar vein, bilberry has been shown to prevent platelet aggregation⁸⁷ as has peony.⁸⁸ However, none of these three herbs has been documented to help atherosclerosis in human trials.

Butcher’s broom and rosemary are not well studied as being circulatory stimulants but are traditionally reputed to have such an action that might impact atherosclerosis. While butcher’s broom is useful for various diseases of veins, it also exerts effects that are protective for arteries.⁸⁹

Preliminary research shows that chondroitin sulfate may prevent atherosclerosis in animals and humans and may also prevent heart attacks in people who already have atherosclerosis.^{90 , 91} However, further research is needed to determine the value of chondroitin sulfate supplements for preventing or treating atherosclerosis.

Though low levels (2 grams per day) of evening primrose oil appear to be without action,⁹² 3–4 grams per day have lowered cholesterol in double-blind research.⁹³ Lowering cholesterol levels should in turn reduce the risk of atherosclerosis.

Preliminary research shows that chondroitin sulfate may prevent atherosclerosis in animals and humans and may also prevent heart attacks in people who already have atherosclerosis.^{94 , 95} However, further research is needed to determine the value of chondroitin sulfate supplements for preventing or treating atherosclerosis.

The research on ginger’s ability to reduce platelet stickiness indicates that 10 grams (approximately 1 heaping teaspoon) per day is the minimum necessary amount to be effective.⁹⁶ Lower amounts of dry ginger,⁹⁷ as well as various levels of fresh ginger,⁹⁸ have not been shown to affect platelets.

Ginkgo may reduce the risk of atherosclerosis by interfering with a chemical the body sometimes makes in excess, called platelet activating factor (PAF).⁹⁹ PAF stimulates platelets to stick together too much; ginkgo stops this from happening. Ginkgo also increases blood circulation to the brain, arms, and legs.¹⁰⁰

Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind¹⁰¹ and other controlled¹⁰² 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,¹⁰³ ginkgo,¹⁰⁴ and guggul¹⁰⁵ are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans.

The carotenoid, lycopene, has been found to be low in the blood of people with atherosclerosis, particularly if they are smokers.¹⁰⁶ Although no association between atherosclerosis and blood level of any other carotenoid (e.g., beta-carotene) was found, the results of this study suggested a protective role for lycopene. Lycopene is present in high amounts in tomatoes.

Turmeric’s active compound curcumin has shown potent anti-platelet activity in animal studies.¹⁰⁷ It has also demonstrated this effect in preliminary human studies.¹⁰⁸ In a similar vein, bilberry has been shown to prevent platelet aggregation¹⁰⁹ as has peony.¹¹⁰ However, none of these three herbs has been documented to help atherosclerosis in human trials.

Quercetin, a flavonoid, protects LDL cholesterol from damage.¹¹¹ While several preliminary studies have found that eating foods high in quercetin lowers the risk of heart disease,^{112, 113, 114} the research on this subject is not always consistent,¹¹⁵ and some research finds no protective link.¹¹⁶ Quercetin is found in apples, onions, black tea, and as a supplement. In some studies, dietary amounts linked to protection from heart disease are as low as 35 mg per day.

Preliminary studies have found that people who drink red wine, which contains resveratrol, are at lower risk of death from heart disease. Because of its antioxidant activity and its effect on platelets, some researchers believe that resveratrol is the protective agent in red wine.^{117 , 118 , 119} Resveratrol research remains very preliminary, however, and as yet there is no evidence that the amounts found in supplements help prevent atherosclerosis in humans.

Butcher’s broom and rosemary are not well studied as being circulatory stimulants but are traditionally reputed to have such an action that might impact atherosclerosis. While butcher’s broom is useful for various diseases of veins, it also exerts effects that are protective for arteries.¹²⁴

Though it has not been studied, shelled hemp seed or its oil may theoretically be useful for people with atherosclerosis due to its content of essential fatty acids.¹²⁵

Turmeric’s active compound curcumin has shown potent anti-platelet activity in animal studies.¹²⁶ It has also demonstrated this effect in preliminary human studies.¹²⁷ In a similar vein, bilberry has been shown to prevent platelet aggregation¹²⁸ as has peony.¹²⁹ However, none of these three herbs has been documented to help atherosclerosis in human trials.

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research,^{130 , 131} though uncertainty remains about whether elevated homocysteine actually causes heart disease.^{132 , 133} Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes,¹³⁴ evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, vitamin B12, and folic acid are associated with low levels of homocysteine¹³⁵ and supplementing with these vitamins lowers homocysteine levels.^{136 , 137}

While several trials have consistently shown that B6, B12, and folic acid lower homocysteine, the amounts used vary from study to study. Many doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid. Even researchers finding only inconsistent links between homocysteine and heart disease have acknowledged that a B vitamin might offer protection against heart disease independent of the homocysteine-lowering effect.¹³⁸ In one trial, people with normal homocysteine levels had demonstrable reversal of atherosclerosis when supplementing B vitamins (2.5 mg folic acid, 25 mg vitamin B6, and 250 mcg of vitamin B12 per day).¹³⁹ Similar results were seen in another study.¹⁴⁰

For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective.¹⁴¹ Of these four supplements, folic acid appears to be the most important.¹⁴² Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.¹⁴³

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research,^{144 , 145} though uncertainty remains about whether elevated homocysteine actually causes heart disease.^{146 , 147} Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes,¹⁴⁸ evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, vitamin B12, and folic acid are associated with low levels of homocysteine¹⁴⁹ and supplementing with these vitamins lowers homocysteine levels.^{150 , 151}

While several trials have consistently shown that B6, B12, and folic acid lower homocysteine, the amounts used vary from study to study. Many doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid. Even researchers finding only inconsistent links between homocysteine and heart disease have acknowledged that a B vitamin might offer protection against heart disease independent of the homocysteine-lowering effect.¹⁵² In one trial, people with normal homocysteine levels had demonstrable reversal of atherosclerosis when supplementing B vitamins (2.5 mg folic acid, 25 mg vitamin B6, and 250 mcg of vitamin B12 per day).¹⁵³ Similar results were seen in another study.¹⁵⁴

For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective.¹⁵⁵ Of these four supplements, folic acid appears to be the most important.¹⁵⁶ Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.¹⁵⁷

Vitamin E is an antioxidant that serves to protect LDL from oxidative damage¹⁵⁸ and has been linked to prevention of heart disease in double-blind research.¹⁵⁹ Many doctors recommend 400–800 IU of vitamin E per day to lower the risk of atherosclerosis and heart attacks. However, some leading researchers suggest taking only 100–200 IU per day, as studies that have explored the long-term effects of different supplemental levels suggest no further benefit beyond that amount, and research reporting positive effects with 400–800 IU per day have not investigated the effects of lower intakes.¹⁶⁰ In a double-blind trial, people with high cholesterol who took 136 IU of natural vitamin E per day for three years had 10% less progression of atherosclerosis compared with those taking placebo.¹⁶¹