Most people are interested in stalling the aging process, or at least in growing old healthfully. To that end, we’ve been hearing about free radicals, reactive atoms that have been implicated in some sixty age-related conditions, including Alzheimer’s disease, cataracts, and heart disease.
Normally, free radicals play an important role in good health. They kill bacteria, fight inflammation, and keep the smooth muscles well-toned to regulate the blood vessels and organs. But when too many free radicals form, they create a dangerous chain reaction that damages healthy cells, opening the door to illness.
The body keeps free radicals in check by producing antioxidants, substances that neutralize the roving atoms and keep them at bay. But it doesn’t produce enough antioxidants to fight off the huge amount of free radicals created in reaction to pollution and other environmental factors.
Scientists generally agree that taking antioxidant supplements may help the body defend itself. Vitamin E, vitamin C, and beta-carotene have been shown to neutralize free radicals by binding their lone electrons. Many herbs also contain antioxidants. The most potent herbal antioxidants are known as flavonoids, substances found in all plants, and some scientists suggest that flavonoids may be even more potent antioxidants than vitamin E.
Four herbal antioxidants have been so extensively researched that we have established a general “tissue-specific” effect for them (see the chart in the images gallery). Beneficial effects of the flavonoids found in three herbs—ginkgo, bilberry, and milk thistle—are well-documented, and brief summaries of those antioxidants are offered here. Hawthorn is not as well-known to the general public, but research into its heart-benefiting antioxidants is promising, and may soon bring this herb into the spotlight.
From this small, shrublike tree with sharp thorns comes antioxidants that help keep the heart healthy.
The hawthorn plant thrives in woodlands, and more than 100 species of Crataegus are found throughout Europe, Western Asia, and North Africa. In Europe, the two species used most often for medicinal purposes are C. laevigata (also referred to as C. oxyacantha) and C. monogyna.
In previous centuries, hawthorn was used to treat illnesses ranging from stomach ailments to dropsy. But it has been used more continuously to treat heart ailments. Practitioners of Asian and European medical traditions have used it for centuries to treat hypertension, arteriosclerosis, and angina pectoris. Although largely absent from American and European medical literature of the late nineteenth century, by 1931, in A Modern Herbal, Maud Grieve mentions using the dried fruits, or “haws”, as a tonic for chronic heart ailments.
The development of modern hawthorn extracts began when European researchers discovered “oligomeric procyanidins”—a complex of flavonoids—inside hawthorn. Research shows that this complex helps the heart pump efficiently by increasing blood supply to the heart muscle, by increasing the heart’s output of blood, and by decreasing blood vessels’ resistance to normal blood flow. The result is a stronger, healthier heart and improved blood circulation.
Hawthorn extracts have successfully been used to treat the early stages of congestive heart failure (CHF). In the early 1990s, German researchers conducted an eight-week study involving thirty early-stage CHF patients aged fifty to seventy. Participants were given either a daily dose of 160 mg of hawthorn extract prepared from leaves and flowers (standardized to contain 18.75 percent oligomeric procyanidins) or a placebo. At the beginning of the study, at four weeks, and again at eight weeks, participants exercised on a stationary bicycle for as long as they could. Researchers then measured blood pressure, heart rate, exercise tolerance, and endurance.
After eight weeks, researchers found that participants taking the hawthorn extract could exercise for a significantly longer period of time before reaching exhaustion than those taking a placebo. Participants taking the hawthorn also reported increased endurance and feelings of well-being.
Six studies conducted during the 1990s with early-stage CHF patients produced similar results: Exercise tolerance improved, and shortness of breath and post-exercise fatigue decreased. These studies also showed that most participants’ heart function improved, and that hawthorn extract compares favorably to the cardiac drug captopril in the treatment of early-stage CHF patients. Captopril enhances blood flow in the peripheral arteries.
Hawthorn also combats angina pectoris, a painful condition resulting from both insufficient blood flow and decreased oxygen supply to the heart muscle. Physical exertion or stress can trigger angina attacks. In a 1983 study in Germany, sixty angina patients were given a daily dose of either 180 mg of hawthorn extract or a placebo for three weeks. The patients taking hawthorn exercised on stationary bicycles for longer periods of time without an angina attack than those taking a placebo. Their ECG measurements improved, as did blood flow and oxygen delivery to the heart muscle.
Bilberry, a close relative of the American blueberry, possesses antioxidants that benefit eyesight.
Bilberry resembles a shrub, growing to about one foot tall, and medicinal extracts come from its ripe fruits, which are usually picked between July and September. Bilberry grows in the woods and forest meadows of northern Europe and the sandy areas of Canada and the United States.
Modern medical research on bilberry began during World War II, when British Royal Air Force pilots noted that their night vision improved when they ate bilberry jam before nighttime bombing raids. Research conducted during the past twenty years clearly points to bilberry’s flavonoids as being responsible for its medicinal properties, particularly a group of complex flavonoids known as anthocyanosides. Studies conducted during the 1960s using rabbits showed that anthocyanosides help regenerate rhodopsin, a purple pigment needed for night vision and adaptation to light. The studies also showed that anthocyanosides protect tiny blood vessels from free radical damage and stimulate the formation of healthy connective tissue.
In Italy, extracts of the bilberry fruit are used to treat diabetic retinopathy, a leading cause of blindness among diabetics, characterized by damage to the retina’s capillaries, and other degenerative retinal conditions.
Ginkgo is one of the top-selling herbs in the United States. Many studies show that ginkgo extract exerts antioxidant activity in the brain, retina, and cardiovascular system.
Native to China and Japan, the ginkgo tree is known for its leathery, fan-shaped leaves, from which the medicinal extracts are made. Scientific studies of ginkgo extract began in earnest during the late 1950s, when researchers in Germany began exploring the herb’s active constituents. Since then, more than 400 studies, reports, and books about ginkgo’s medicinal benefits have been published.
Ginkgo contains the flavonoids quercetin, kaempferol, and isorhamnetin. They provide its antioxidant power and its ability to keep blood platelets from sticking together. Together, these actions prevent circulatory arteriosclerosis and other diseases that affect the brain and central nervous system. Ginkgo also possesses two unique flavonoids—ginkgolides and bilobalides. Research shows that ginkgolides moderate overproduction of platelet-activating factor, which activates immune cells responsible for blood clotting. Bilobalides protect nerve cells, and an animal study conducted in 1994 in Germany shows that they may help regenerate damaged nerve cells.
Because ginkgo’s ability to increase circulation to the brain and central nervous system is well-documented, it has been used against depression and memory loss in the elderly. It is a promising herbal remedy for age-related declines in brain function, and in the prevention and early treatment of Alzheimer’s disease and strokes.
Milk thistle is commonly found growing wild in a variety of settings, including roadsides. Its seeds hold antioxidants that have been shown to protect the liver.
Thirty years ago, researchers in Germany began an intensive investigation into the liver-protecting properties of milk thistle seeds, long reputed to be a surefire remedy for liver ailments. In 1968, they identified a flavonoid complex in milk thistle seed that is responsible for the plant’s medical benefits and christened it “silymarin”.
Silymarin helps liver cells produce a powerful antioxidant known as glutathione; it has been shown to raise glutathione levels in liver cells by as much as 50 percent.
Silymarin also increases the activity of another antioxidant, superoxide dismutase, in red blood cells. The German government has endorsed a standardized milk thistle extract to use in the treatment of alcohol-induced liver disease and other chronic liver diseases. So far, more than 200 clinical studies conducted primarily in Germany have been completed with this extract. They show that silymarin protects the liver by binding to the outside of liver cells to block certain toxins from entering. It also neutralizes toxins that have already penetrated the liver cell.
Onions, cayenne pepper, garlic, and black and green tea are but a few of the herbal sources of quercetin, a flavonoid shown to prevent cardiovascular disease and arteriosclerosis, a condition in which fatty deposits accumulate in the lining of the arteries, making it difficult for blood to flow smoothly.
Quercetin inhibits the production of free radicals in the cardiovascular system and prevents free radicals from oxidizing low-density lipoproteins (LDL), or “bad” cholesterol, which leads to artery damage, arteriosclerosis, and heart disease. This flavonoid also cleans excess iron from the circulatory system and slows the buildup of platelets in the bloodstream. Excess iron and “sticky” platelets are among the risk factors for arteriosclerosis and coronary artery disease.
Quercetin’s ability to prevent cardiovascular disease has been demonstrated in two large population studies. The first, called the “Zutphen Elderly Study”, investigated risk factors for chronic disease in 805 elderly Dutch men aged sixty-five to eighty-four. In 1985, researchers took stock of the participants’ intake of quercetin and other flavonoids, including kaempferol and myricetin. For five years, the researchers tracked the participants, whose major sources of flavonoids were tea, onions, and apples.
The researchers found that flavonoid intake decreased mortality from coronary heart disease and, to a lesser extent, decreased the incidence of a first heart attack. Even if the participants had problems with weight, smoking, cholesterol level, blood pressure, physical exercise, coffee consumption, and intake of vitamin C, vitamin E, beta-carotene, and dietary fiber, the incidence of a first heart attack was reduced. Researchers also found that flavonoid intake was linked to a decreased risk of stroke, and that men with the largest flavonoid intake (more than 30 mg daily) had about one-third the risk of cardiovascular disease as men with the lowest intake of flavonoids.
Quercetin was the predominant flavonoid consumed by men in the study and was most significantly correlated with a reduced risk of cardiovascular disease.
The second study, the “Seven Countries Study”, took place between 1958 and 1964. Researchers followed 763 men aged forty to fifty-nine living in Finland, Italy, Greece, the former Yugoslavia, Japan, Netherlands, and the United States. Flavonoid intake was determined by dietary analysis of food composites representing the average diet in each country. In this study as in the other, researchers associated flavonoid intake with decreased death rates from coronary heart disease; quercetin was associated with a protective effect in men consuming higher amounts.
For more information about quercetin, see “Inside Plants” in the March/April 1997 issue of Herbs for Health.
The reference list for this article is quite extensive. If you would like a copy, write to Herbs for Health, Antioxidant Reference List.
Donald Brown is a naturopathic physician who lives in Seattle, Washington. A faculty member of Bastyr University, he is the founder and director of Natural Product Research Consultants, editor of the Quarterly Review of Natural Medicine, and author of Herbal Prescriptions for Better Health (Prima Publishing, 1996).
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