Deciphering the Power of Antioxidants

References

The aging process brings with it degenerative states such as cardiovascular disease, cancer, macular degeneration and Alzheimer's disease. While the onset of these conditions is influenced by genetics, both lifestyle and environmental factors also play major roles in the body's ability to remain healthy long-term and fight aging. Since Denham Harman, M.D., Ph.D., first proposed the "free radical" theory of aging in the 1950s, nutritionists have sought to understand the body's oxidation process and how to prevent damage caused by rogue oxygen molecules.

There is growing evidence that the production of reactive oxygen species (ROS), including free radicals, is behind the aging process and initiation of age-related disease. Phagocytes (white blood cells) produce ROS in response to infection or damage by external factors like environmental toxins. These free radicals attack the foreign proteins or mutated cells; however, after the immediate threat is extinguished, ROS can remain in the system, impacting healthy cells.

These free radicals have an unpaired electron, a situation the free radical remedies by stealing an electron from a stable molecule. This sets off a chain reaction that can damage the body's proteins and cell membranes, weaken the cells' natural defenses and disrupt cells' DNA. Accumulated damage can lead to widespread biomolecular changes, leaving the body susceptible to degenerative disease conditions.

Luckily, nature provided a system to help control free radicals. Antioxidants quench free radicals by donating electrons to molecules before they damage other cells. Studies have indicated certain antioxidants may have additional activities, such as reducing the energy of a free radical or stopping it from forming by interrupting an oxidizing chain reaction. Antioxidants may also trap free radicals and lipid peroxides, delaying the onset of lipid peroxidation, stalling production of further free radicals and inhibiting the damaging effects of certain enzymes that can degrade connective tissues.

Antioxidants can be endogenous (produced by the body) or exogenous (obtained through the diet). Endogenous antioxidants include enzymes, coenzymes and sulfur-containing compounds such as glutathione. Exogenous antioxidants include vitamins C and E, bioflavonoids and carotenes. In fact, the term "antioxidant" is applied to dozens of different kinds of nutrients, botanicals and supplements, from grapeseed extract and selenium to alpha-lipoic acid and superoxide dismutase.

Researchers have spent years exploring the impact of oxidation in the body and the effects of antioxidants, but the connection in humans is still unproven. "Oxidation of biomolecules may play a role in susceptibility to a number of diseases," wrote researchers from the University of California, Berkeley, in the American Journal of Epidemiology.¹ "However, there are few large-scale survey data describing oxidative damage that occurs in humans and the demographic, physical or nutritional factors that may be associated with it."

National health organizations have developed information sheets for interested consumers about antioxidants and disease conditions. The American Heart Association (AHA), for example, notes, "increasing evidence suggests that LDL cholesterol lipoprotein oxidation and its biological effects can be prevented by using antioxidants--both in the diet and in supplements." While AHA noted there is strong evidence for the role of vitamin E in lowering the risk of coronary heart disease and LDL oxidation, it stopped short of recommending antioxidant vitamin supplements "until more complete data are available."

The National Cancer Institute (NCI) took a similar position in its fact sheet on antioxidants and cancer prevention. It allowed that considerable evidence from chemical, cell culture and animals studies indicates antioxidants may slow or prevent cancer development, but added human clinical trials have been inconsistent. The Chinese Cancer Prevention Study, published in 1993, showed a combination of beta-carotene, vitamin E and selenium reduced the incidence of cancer, whereas the CARET studies of 1994 and 1996 showed an increase of lung cancer associated with beta-carotene. NCI is funding research investigating the impact of antioxidants on cancer, including the Selenium and Vitamin E Cancer Prevention Trial and the Physicians' Health Study II.

Researchers are hoping these clinical studies, as well as other in vitro experiments, will add to the positive findings about many types of antioxidants. At this point, some of the most prominent compounds include vitamins C and E, minerals zinc and selenium, and a host of botanical and specialty extracts.

Vitamins & Minerals

Vitamin C is perhaps the most famous antioxidant. Also known as ascorbic acid, vitamin C is found in abundance in fruits and vegetables, as well as in cereals, beef, poultry and fish. It prevents oxidation of water-soluble molecules and is a particularly effective antioxidant in the liquid-based areas of the body, including blood plasma, lung fluid, eye fluids and in between cells. Epidemiological studies have shown that diets high in vitamin C substantially cut the risk of most cancers and can protect against heart disease by neutralizing free radicals that oxidize LDL cholesterol.

A research review published out of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, a part of the National Institutes of Health), reviewed the impact of vitamin C in the body.² "Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro," the researchers wrote. "[However] the relationship of oxidant markers to human disease conditions is not clear ... [and] intervention studies with vitamin C have shown no change in markers of oxidation or clinical benefit." They encouraged future studies with patient groups known to have increased oxidative damage to investigate the antioxidant effects of vitamin C.

While vitamin C works in the water-soluble molecules, vitamin E is a fat-soluble vitamin most significantly present in the lipids of cell membranes and in circulating LDL cholesterol. Vitamin E exists naturally in eight different isomers--four tocopherols (alpha-, beta-, gamma- and delta-) and four tocotrienols (alpha-, beta-, gamma- and delta). Alpha-tocopherol is acknowledged to be the preferred form in the body, and most studies have used straight alpha-tocopherol rather than mixed tocopherols/tocotrienols.

Unlike other vitamins, synthetic alpha-tocopherol (known as dl-alpha-tocopherol) is not identical to the natural (d-alpha-tocopherol) form, and is not quite as active as the natural form. Also, some studies using synthetic vitamin E have not shown significant benefits in reducing LDL oxidation or risk of cardiovascular disease. Researchers have speculated it may be due to either the reduced activity of the synthetic form, or the lack of the full spectrum of isomers in the vitamin E used.

Support for the ingestion of a full range of natural vitamin E isomers can be found in the January 2003 Harvard Health Letter, which reported on a dozen centenarian studies, including one based at Harvard. The authors reviewed a study in Italy that found healthy centenarians had exceptionally higher blood levels of vitamin E compared with healthy younger adults. They proposed that "vitamin-rich blood may both strengthen the immune system of these centenarians and defend them against damage done by free radicals."

Combinations of vitamins C and E have also shown, in some cases, to be more powerful than either alone. Richard Passwater, Ph.D., coined the term "antioxidant synergism" in the 1960s. He explained in All About Antioxidants (Avery Publishing, 1998) this is when the whole is greater than the sum of the parts. "Different antioxidants protect against different types of free radicals in different parts of cells and in different places in the body," he wrote.

Recent studies have illustrated the ability of the fat-soluble E and water-soluble C to work together. For example, a study in Taiwan on 38 hemodialysis patients indicated 400 mg/d vitamin C plus 400 mg/d vitamin E significantly increased plasma vitamin C and E, erythrocyte glutathione (an endogenous antioxidant protein formed from the amino acids cysteine, glutamic acid and glycine) and plasma antioxidant status; it also inhibited plasma lipid peroxides compared with placebo.³ Researchers further found the effects continued up to two weeks after ceasing supplementation. Another study, conducted at King's College in London, looked at women at risk of preeclampsia, and found a combination of 1,000 mg/d of vitamin C and 400 IU/d of vitamin E improved the biochemical indices of the disease.⁴

While vitamins C and E have direct antioxidant actions in the body, minerals primarily serve as components of the body's own antioxidant enzymes and other compounds. Selenium, for example, inhibits hydrogen peroxide as a component of the endogenous antioxidant enzyme glutathione peroxidase, formed from selenium and glutathione. Selenium further potentiates the antioxidant activity of vitamin E, working to protect the cardiovascular system.

On its own, selenium has been studied for how it contributes to antioxidant activity in the body. In particular, it appears to protect against cancer, and there are currently several pending trials about selenium and prostate cancer. One recent study found selenium prevented DNA damage in prostate tissue in dogs and increased epithelial cell apoptosis in the prostate.⁵ Selenium is also protective against neurological damage, as a study out of India found it could slow down neuronal injury in a rat model of Parkinson's disease by upregulating antioxidant activity.⁶

Another important mineral for antioxidant protection is zinc, which prevents lipid oxidation. In addition, it is a constituent of the antioxidant enzyme superoxide dismutase (SOD). Zinc is also needed for proper maintenance of vitamin E levels in the blood and aids in the absorption of vitamin A. A preliminary study from the Agricultural Research Service, conducted at the University of California, Berkeley, found zinc may safeguard red blood cell membranes against oxidative effects of other minerals. Zinc may also serve as an antioxidant for the skin, protecting against UV radiation that can cause free radical-induced oxidative damage. Researchers from Duke University in Durham, N.C., suggest zinc ions may replace redox active molecules at critical sites in cell membranes and proteins, or they may induce synthesis of sulfhydryl-rich proteins that protect against free radicals.⁷

Research conducted by Benicia, Calif.-based InterHealth on its patented L-OptiZinc® (a zinc-methionine complex) has shown positive effects on oxidative damage. For example, a 1998 study at Creighton University in Omaha, Neb., showed L-OptiZinc IH121 provided significantly greater protection against free radicals and free radical-induced lipid peroxidation and DNA damage in vivo than other zinc supplements tested.

Botanicals

Many plants have oxidative protection provided by their fat-soluble pigments known as carotenoids. However, there are many other compounds in plants that can protect against oxidative damage. Flavonoids, for example, are chemical compounds produced by plants to protect themselves from foreign invasion and cell damage. There are more than 4,000 chemically unique flavonoids found in fruits, vegetables, spices, seeds, nuts, flowers and bark. Best known of the flavonoids are the polyphenols, found in such foods as tea and wine.

Green tea, for example, is a rich source of the flavonoid derivatives (polyphenols) epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG). Green tea is produced from steaming fresh leaves at high temperatures, thereby inactivating the oxidizing enzymes and leaving the polyphenol content intact. Polyphenols appear to prevent formation of peroxide free radicals--including inhibiting oxidation of LDL cholesterol--and to regenerate vitamin E in the body.

In vitro studies have shown positive results from green tea extract improving muscle health through its antioxidant protection⁸ and correcting imbalances in the body's antioxidant system, thereby protecting organ function.⁹ Also, it appears green tea extract has direct scavenging activity against nitric oxide and superoxide-generating systems in vitro.¹⁰ Results from human clinical studies have been inconsistent regarding tea's antioxidant activity. A study in Sendei, Japan, showed an increase in antioxidant capacity of plasma in 18 healthy volunteers given green tea extract.¹¹ However, another study out of Japan's National Institute of Health & Nutrition did not reveal an increase in plasma antioxidant activity in five women after ingestion of tea catechins for seven days.¹²

Flavonoids can also be found in grapeseed extract, specifically the proanthocyanidins--condensed tannins also known as oligomeric proanthocyanidins (OPCs). Proanthocyanidins have been associated with the term "French Paradox," or the observation that a high dietary intake of fats in France is not associated with an increase in atherosclerosis and other cardiovascular diseases due to the antioxidant effects of wine consumption. In vitro studies report grapeseed OPCs are approximately twice as powerful as vitamin E and as much as four times stronger than vitamin C. They may enhance absorption of and work synergistically with vitamin C, and have been reported to actually spare vitamin E from oxidation in vitro.

One recent human clinical study examined the ability of grapeseed extract to increase plasma antioxidant capacity and reduce oxidative stress. Italian researchers gave eight healthy volunteers a meal rich in oxidized and oxidizable lipids with or without 300 mg/d of grapeseed extract.¹³ They found plasma antioxidant capacity increased in postprandial phase in those subjects given grapeseed extract, and concluded the extract minimized oxidative stress and enhanced resistance to LDL oxidation.

Patented grapeseed formulas have also been published. A review article about ActiVin GSPE (supplied by Fresno, Calif.-based San Joaquin Valley Concentrates) stated, "We have demonstrated that IH636 proanthocyanidin extract (GSPE) provides excellent protection against free radicals in both in vitro and in vivo models."¹⁴ Another study from the same researchers determined GSPE protected against induced oxidative stress, DNA damage and apoptotic cell death.¹⁵

Another study reported in the Journal of Medicinal Food investigated a commercial grapeseed extract (MegaNatural® Gold from Madera, Calif.-based Polyphenolics) along with grapes, grape juice, red wine and other grapeseed extracts, and found high plasma antioxidant activity in subjects taking 600 mg/d of the commercial grapeseed extract.¹⁶ Subjects with high cholesterol also showed a change in plasma total, LDL and HDL cholesterol concentrations. Another study, presented at the American Chemical Society National Meeting in March 2000, showed grapeseed extract (as MegaNatural Gold) had great antioxidant capacity, as well as synergism with vitamins C and E.¹⁷

The seeds of grapes are not the only portion of the fruit purported to have antioxidant activity. Resveratrol, a phenolic constituent found in the skin of grapes, is part of another group of compounds called phytoalexins, which are produced in plants during times of environmental stress. Studies conducted by BioSerae Laboratories in Bram, France, have shown the company's Resveravine® prevents oxidation of LDL in vitro, and was 2.7 times more effective than catechins and 4.2 times more so than vitamin E.

Beyond the French Paradox, red wine plays a role in the "Mediterranean Diet," which has been linked to lower rates of heart disease and chronic disease. The diet also includes olive oil, seen as a heart-healthy fat due to its antioxidant content. While polyphenols are present in extracted olive oil, olive water contains even higher concentrations of these polyphenols. High-quality, extra virgin olive oil may contain between 100 and 300 mcg of polyphenols per liter of oil, while the concentration in olive water is 300- to 500-times greater.

Hydroxytyrosol is the active portion of oleuropein, the antioxidant found in olive leaf. Compared to oleuropein, hydroxytyrosol has significantly higher antioxidant capacity, according to laboratory tests. Brunswick Labs in Wareham, Mass., tested the Oxygen Radical Absorbance Capacity (ORAC) of both compounds and showed 27,000 ORAC for HIDROX™ (the trademarked form available from Hayward, Calif.-based CreAgri) versus 12,200 ORAC for olive leaf. And a rat study using a hydroxytyrosol-rich olive mill waste water (OMWW) extract (10 mg/kg) demonstrated that hydroxytyrosol was dose-dependently absorbed and was associated with an increase of plasma antioxidant capacity.¹⁸

Another rich source of antioxidants is pine bark extract, which contains high levels of OPCs. Pycnogenol™ (available from Hillside, N.J.-based Natural Health Science) standardized French maritime pine bark extract delivers procyanidins and phenolic acids. It has been extensively studied for its antioxidant capacity and role in preventing many degenerative conditions. "Pycnogenol protects against oxidative stress in several cell systems by doubling the intracellular synthesis of antioxidative enzymes and by acting as a potent scavenger of free radicals," according to a review out of Westfalische Wilhelms-Universitat in Munster, Germany.¹⁹ "Other antioxidant effects involve a role in the regeneration and protection of vitamins C and E."

The conditions for which Pycnogenol has been studied include cardiovascular disease and cognitive function. A recent clinical study out of the University of California, Davis, found 150 mg/d of Pycnogenol significantly increased the antioxidant capacity of plasma and exerted favorable effects on blood lipids.²⁰ Its antioxidant ability to protect cells from cytotoxicity was suggested by researchers from the University of California, Berkeley, which may explain its role in benefiting neurological disorders such as Alzheimer's disease.²¹ Also, it appears to reduce Abeta-induced apoptosis, a pathological feature of Alzheimer's.²²

The botanical world also offers antioxidant protection in many herbs and spices. Extracts from spices such as cumin, sage and oregano all act as potent antioxidants, protecting fats from degenerating. Researchers have also found clove, oregano and thyme oils are highly protective against cellular oxidation. Wild oregano has been shown in studies to directly destroy viruses, parasites, bacteria and fungi before they can cause oxidative damage. And rosemary contains two antioxidant constituents: carnosic acid is fat-soluble and works to reduce LDL peroxidation, while rosemarinic acid is water-soluble and reduces platelet aggregation.

Specialty Compounds

Also coming out of nature are antioxidants found in many products of the bee hive, including honey, bee pollen and propolis. A study from the University of Illinois, Urbana, characterized the phenolics and other antioxidants present in honeys from different floral sources and found a correlation between protein content and ORAC activity.²³ Bee pollen (as High Desert® Bee Pollen from Phoenix-based C.C. Pollen Co.) also has been shown to have high ORAC values. Testing conducted by Brunswick Labs found an ORAC value of 247 umole TE/g for High Desert Bee Pollen; the closest ORAC value in its testing was for black raspberry at 164 umole TE/g. Bee pollen also has high levels of polyphenols; researchers from the University of Technology in Vienna, Italy, found natural bee-collected flower pollen contains "remarkable" amounts of polyphenol compounds and suggested further investigations be performed to "evaluate the role and contribution [of pollen and pollen extracts] in regard to their antioxidative and radical scavenging activity."²⁴

Propolis--tree resins combined with bee secretions that form the "immune system" of the hive--is being studied for its antioxidant properties as well. Italian researchers have broken down the compounds of propolis, including amino acids, phenolic acids, phenolic acid esters, flavonoids, cinnamic acid, terprenes and caffeic acid.²⁵ They found propolis containing caffeic acid phenethyl ester (CAPE) showed higher antioxidant activity than that without. Belgian researchers reached similar conclusions, finding caffeic acid esters had "interesting" antioxidant activity.²⁶ This activity may include regeneration of vitamin C and specific activity in the kidney and gastrointestinal tract.²⁷

Superoxide dismutase (SOD), as mentioned in the discussion about zinc, is an enzyme that revitalizes cells and reduces the rate of cell destruction. It neutralizes the most common free radicals, known as superoxide radicals. SOD has strong regenerative effects on tissues that have become hardened or fibrotic because of age, disease or injury. Because it has the capacity to revitalize cells and help maintain a normal rate of cell turnover, SOD's most promising application may be in anti-aging, since cells lose the ability to produce SOD as the body ages. SOD occurs naturally in many green plants, including broccoli and barley grass, and is available in supplement form. It is recommended SOD be taken in enteric-coated form to allow the pill to pass into the small intestine before being absorbed.

Coenzyme Q10 (CoQ10) is also known as ubiquinone and is a powerful group of lipid-soluble compounds. It is known to inhibit lipid peroxidation in both cell membranes and serum LDL, and may offer protection from oxidative damage. It is found in the highest concentrations in the heart, where it helps the cellular mitochondria metabolize fats for energy, and it helps maintain the flexibility of cell membranes. CoQ10 levels decline in mitochondria as the body ages, which led Italian researchers to speculate that heavier (older) mitochondria with less CoQ10 have a higher hydroperoxide content and a smaller loss of fatty acids, particularly in the brain.²⁸

The ability of CoQ10 to work as an antioxidant in preventing neurodegenerative diseases is a research focus. Researchers out of the Albert Einstein College of Medicine in Bronx, N.Y., found CoQ10 prevented the death rate of oligodendrocytes, which form myelin protein sheets in the nervous system.²⁹ It also restored the number of mature myelin basic protein-positive cells. These actions, together with its actions in the mitochondria, led other researchers to investigate the usefulness of CoQ10 in animal models of neuro-diseases such as Alzheimer's and Parkinson's; they found it protected against lesions produced by mitochondrial toxins.³⁰

Additional promising research with CoQ10 and Parkinson's disease came out of the University of California, San Diego.³¹ The phase II clinical trial indicated supplementation with 1,200 mg/d of CoQ10 stalled cognitive decline by 44 percent compared to placebo. Lower doses (300 mg/d and 600 mg/d) also reduced the rate of mental decline, but not to the same extent as the high-dose group. [Editor's note: The CoQ10 product used in this study was a special formulation developed by Enzymatic Therapy. The company produced a wafer form of its Vitaline CoQ10 with 1,200 mg of natural CoQ10 and 1,200 mg of vitamin E, using a patent-pending manufacturing process to enhance absorption without use of excipients that can be neurologically harmful at high doses.]

Researchers in Poland compared the possible protective effects of CoQ10 with those of the sulfur-containing antioxidant compound alpha-lipoic acid (ALA) for reducing neuronal cell death.³² The researchers invoked diabetes in rats and then induced cerebral ischaemia in some of them. Then, all animals were either treated with CoQ10 or ALA for seven days. Both treatments were found to diminish neuronal cell loss in diabetes complicated with ischemia.

As this suggests, ALA is a powerful antioxidant. Some of this vitamin-like substance is converted in the body to dihydrolipoic acid, which quenches free radicals in both lipid and aqueous domains. ALA stimulates the body's production of glutathione and aids in the absorption of CoQ10, and also regenerates vitamins C and E. Researchers have also found this may stimulate glucose uptake into adipocytes by increasing intracellular oxidant levels or oxidizing thiol groups,³³ and may enhance the antioxidant defenses and function of endothelial cells, which are often dysfunctional in degenerative diseases.³⁴

As mentioned earlier, the idea of antioxidant synergism promotes taking in a range of antioxidants to offer the broadest defense against oxidative damage. As such, researchers are exploring the power of antioxidant combinations. For example, researchers from Loyola University Medical Center in Maywood, Ill., divided volunteers into groups to test three different antioxidant formulas.³⁵ Formula 1 included zinc, selenium, vitamin A, beta-carotene, vitamin E and L-cysteine; formula 2 had citrus bioflavonoids, vitamin C, CoQ10 and vitamin B6; formula 3 had all ingredients. The researchers found that when the antioxidants were taken in combination, all formulas reduced oxidative stress, with very little relevant pro-oxidant activity from the intake of the nutrients. Another clinical study, this one out of Italy, sought to determine whether antioxidant formulas could modulate apoptosis.³⁶ A formula with alpha-tocopherol, ALA, CoQ10, carnitines and selenomethionine given to 20 healthy individuals significantly increased plasma antioxidant status, mirrored by a decrease in blood peroxide levels and reduced generation of ROS at a mitochondrial level.

Perhaps Mother Nature does know best--supplying a range of nutrients that can act synergistically in the body to control the toxic side effects of living. Retailers looking to help customers fortify their natural defenses against aging and degenerative disease may do well to help them find broad antioxidant support through a range of compounds.

Carotenoids as Antioxidants

Carotenoids, a class of phytochemicals, are fat-soluble pigments found in yellow, red, green and orange vegetables and fruits. They include such well-known members as beta-carotene, alpha-carotene, lycopene, lutein, astaxathin and zeaxanthin. While there are approximately 700 carotenoids found in nature, about 50 of those can be absorbed and metabolized by the human body. Many, such as beta-carotene, serve as precursors to the fat-soluble vitamin A.

The carotenes have established efficacy in quenching singlet oxygen and intercepting reactive oxygen species, making them an important part of the antioxidant larder. However, they also have many other established physiological activities. They may enhance immune function, reduce mutagenesis and inhibit cell transformations. Epidemiological studies have established an inverse correlation between dietary intake of carotenoids and incidence of some types of cancer.

HSR will take an in-depth look at carotenoids and human health in its June issue.

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