Atherosclerosis is hardening of the arteries, a common disease of the major blood vessels characterised by fatty streaks along the vessel walls and by deposits of cholesterol and calcium.
Atherosclerosis of arteries supplying the heart is called coronary artery disease. It can restrict the flow of blood to the heart, which often triggers heart attacks—the leading cause of death in Americans and Europeans. Atherosclerosis of arteries supplying the legs causes a condition called intermittent claudication, which is characterized by pain in the legs after walking short distances.
People with elevated cholesterol levels are much more likely to have atherosclerosis than people with low cholesterol levels. Many important nutritional approaches to protecting against atherosclerosis are aimed at lowering serum cholesterol levels.
People with diabetes are also at very high risk for atherosclerosis, as are people with elevated triglycerides and high homocysteine.
What are the symptoms of atherosclerosis?
Atherosclerosis is typically a silent disease until one of the many late-stage vascular manifestations intervenes. Some people with atherosclerosis may experience angina (chest pain) or intermittent claudication (leg cramps and pain) on exertion. Symptoms such as these develop gradually as the disease progresses.
Dietary changes that may be helpful.
The most important dietary changes in protecting arteries from atherosclerosis include avoiding meat and dairy fat and avoiding foods that contain trans fatty acids (margarine, some vegetable oils, and many processed foods containing vegetable oils). Increasingly, the importance of avoiding trans fatty acids is being accepted by the scientific community. Leading researchers have recently begun to view the evidence linking trans fatty acids to markers for heart disease as “unequivocal.”
People who eat diets high in alpha-linolenic acid (ALA), which is found in canola and flaxseed oils, have higher blood levels of omega-3 fatty acids than those consuming lower amounts, which may confer some protection against atherosclerosis. In 1994, researchers conducted a study in people with a history of heart disease, using what they called the “Mediterranean” diet. The diet differed significantly from what people from Mediterranean countries actually eat, in that it contained little olive oil. Instead, the diet included a special margarine high in ALA. Those people assigned to the Mediterranean diet had a remarkable 70% reduced risk of dying from heart disease compared with the control group during the first 27 months. Similar results were also confirmed after almost four years. The diet was high in beans and peas, fish, fruit, vegetables, bread, and cereals, and low in meat, dairy fat, and eggs. Although the authors believe that the high ALA content of the diet was partly responsible for the surprising outcome, other aspects of the diet may have been partly or even totally responsible for decreased death rates. Therefore, the success of the Mediterranean diet does not prove that ALA protects against heart disease.
A systematic review of 20 years of research evaluated the association between dietary fibre and coronary heart disease. The meta-analysis portion of this review showed that regular whole grain foods are associated with a coronary heart disease risk reduction of about 26%. In general, the fibres most linked to the reduction of cholesterol levels are found in oats, psyllium seeds, fruit (pectin) and beans (guar gum). An analysis of many soluble fibre trials proves that a cholesterol lowering effect exists, but the amount the cholesterol falls is quite modest. For unknown reasons, however, diets higher in insoluble fibre (found in whole grains and vegetables and mostly unrelated to cholesterol levels) have been reported to correlate better with protection against heart disease in both men and women. Some trials have used 20 grams of additional fibre per day for several months to successfully lower cholesterol.
Independent of their action on serum cholesterol, foods that contain high amounts of cholesterol—mostly egg yolks—can induce atherosclerosis. It makes sense to reduce the intake of egg yolks. However, eating eggs does not increase serum cholesterol as much as eating saturated fat, and eggs may not increase serum cholesterol at all if the overall diet is low in fat. A decrease in atherosclerosis resulting from a pure vegetarian diet (no meat, poultry, dairy or eggs), combined with exercise and stress reduction, and has been proven by controlled medical research.
Preliminary evidence has suggested that excessive salt consumption is a risk factor for heart disease and death from heart disease in overweight people. Controlled trials are needed to confirm these observations.
Eating a diet high in refined carbohydrates (e.g., white flour, white rice, simple sugars) appears to increase the risk of coronary heart disease, and thus of heart attacks, especially in overweight women.17 However, controlled trials of reducing refined carbohydrate intake to prevent heart disease have not been attempted to confirm these preliminary findings.
Lifestyle changes that may be helpful.
Virtually all doctors acknowledge the abundant evidence that smoking is directly linked to atherosclerosis and heart disease. Quitting smoking protects many people from atherosclerosis and heart disease, and is a critical step in the process of disease prevention.
Obesity, type A behaviour (time conscious, impatient, and aggressive), stress, and sedentary lifestyle are all associated with an increased risk of atherosclerosis; interventions designed to change these risk factors are linked to protection from this condition.
Aggressive verbal or physical responses when angry have been consistently related to coronary atherosclerosis in numerous preliminary studies. A low level of social support, especially when combined with a high level of outwardly expressed anger has also been associated with accelerated progression of coronary atherosclerosis.
Nutritional supplements that may be helpful.
Tocotrienols may offer protection against atherosclerosis by preventing oxidative damage to LDL cholesterol. 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.
Supplementation with fish oil, rich in omega-3 fatty acids, has been associated with favourable changes in various risk factors for atherosclerosis and heart disease in some, but not all, studies. 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 regression of atherosclerotic plaques and a decrease in cardiovascular events (e.g., heart attack and stroke) compared with those who did not take fish oil. 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 favourable changes in the diameter of atherosclerotic coronary arteries.
In some studies, people who consumed more selenium in their diet had a lower risk of heart disease. 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. 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.
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. Vitamin C also protects LDL.
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. In a double-blind trial, 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.
Vitamin E is an antioxidant that serves to protect LDL from oxidative damage and has been linked to prevention of heart disease in double-blind research. 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. 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.
Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research, though uncertainty remains about whether elevated homocysteine actually causes heart disease. Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes, 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 homocysteine and supplementing with these vitamins lowers homocysteine levels.
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.61 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).
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. Of these four supplements, folic acid appears to be the most important. Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.
Quercetin, a flavonoid, protects LDL cholesterol from damage. While several preliminary studies have found that eating foods high in quercetin lowers the risk of heart disease, the research on this subject is not always consistent, and some research finds no protective link. 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.
Though low levels (2 grams per day) of evening primrose oil appear to be without action, 3–4 grams per day have lowered cholesterol in double-blind research. Lowering cholesterol levels should in turn reduce the risk of atherosclerosis.
Preliminary research shows that chondroitin sulphate may prevent atherosclerosis in animals and humans and may also prevent heart attacks in people who already have atherosclerosis. However, further research is needed to determine the value of chondroitin sulphate supplements for preventing or treating atherosclerosis.
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. Resveratrol research remains very preliminary, however, and as yet there is no evidence that the amounts found in supplements help prevent atherosclerosis in humans.
In 1992, a Finnish study found a strong link between unnecessary exposure to iron and increased risk for heart disease. Since then many studies have not found that link, though perhaps an equal number have been able to confirm the outcome of the original report. One 1999 analysis of 12 studies looking at iron status and heart disease found no overall relationship, though another 1999 analysis of published studies came to a different conclusion. While the effect of unnecessary exposure to iron, including iron supplements, on the risk of heart disease remains unclear, there is no benefit in supplementing iron in the absence of a diagnosed deficiency.
The carotenoid, lycopene, has been found to be low in the blood of people with atherosclerosis, particularly if they are smokers. 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.
Herbs that may be helpful.
Many actions associated with herbal supplements may help prevent or potentially alleviate atherosclerosis. Herbs such as garlic and ginkgo appear to directly affect the hardened arteries by multiple mechanisms. Herbs such as psyllium, guggul, and fenugreek reduce cholesterol and other lipid levels in the blood—known risk factors for hardened arteries. A related group are herbs, including green tea, prevents the oxidation of cholesterol, an important step in protecting against atherosclerosis. Finally, there are herbs such as ginger and turmeric that reduce excessive stickiness of platelets, thereby reducing atherosclerosis.
Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial. The preparation used, standardized for 0.6% allicin content, provided 900 mg of standardised 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, though more recently, some double-blind trials have not found garlic to be effective. Some of the negative trials have flaws in their design. Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear.
Garlic has also been shown to prevent excessive platelet adhesion in humans. 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. Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans, an event believed to be a significant factor in the development of atherosclerosis.
Ginkgo may reduce the risk of atherosclerosis by interfering with a chemical the body sometimes makes in excess, called platelet activating factor (PAF). PAF stimulates platelets to stick together too much; ginkgo stops this from happening. Ginkgo also increases blood circulation to the brain, arms, and legs. Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind and other controlled trials to decrease the overactive coagulation of blood that may contribute to atherosclerosis.
Guggul has been less extensively studied, but double-blind evidence suggests it can significantly improve cholesterol and triglyceride levels in people. Numerous medicinal plants and plant compounds have demonstrated an ability to protect LDL cholesterol from being damaged by free radicals. Garlic, ginkgo, and guggul are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans.
Several other herbs have been shown in research to lower lipid levels. Of these, psyllium has the most consistent backing from multiple double-blind trials showing lower cholesterol and triglyceride levels. The evidence supporting the ability of fenugreek to lower lipid levels is not as convincing, coming from preliminary studies only.
Since oxidation of LDL cholesterol is thought to be important in causing or accelerating atherosclerosis, and green tea protects against oxidation, this herb may have a role in preventing atherosclerosis. However, while some studies show that green tea is an antioxidant in humans, others have not been able to confirm that it protects LDL cholesterol from damage. Much of the research documenting the health benefits of green tea is based on the amount of green tea typically drunk in Asian countries—about three cups per day (providing 240–320 mg of polyphenols).
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. Lower amounts of dry ginger, as well as various levels of fresh ginger, have not been shown to affect platelets.
Turmeric’s active compound curcumin has shown potent anti-platelet activity in animal studies. It has also demonstrated this effect in preliminary human studies. In a similar vein, bilberry has been shown to prevent platelet aggregation as has peony. 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.