By Roni Enten, MSc, CNS
Each day, every cell in the human body must withstand an estimated 10,000 individual assaults from externally introduced reactive oxygen species (ROS) or free radicals.1
The progressive, system-wide destruction wrought by this continuous biochemical onslaught has been thoroughly documented in the scientific literature. In the older cells of aging animals, to take one example, researchers have found that one out of every three proteins is rendered dysfunctional by unchecked free radical damage.2
In the search for optimal defense against free radicals, scientists have focused intensely on berry extracts. A growing body of scientific evidence shows that berry polyphenols' antioxidant capacity powerfully targets numerous degenerative diseases, from cancer and atherosclerosis to impaired glucose control and blood lipid abnormalities.3-11
Touted commercially for years as a "superfood," only recently has the acai berry gained compelling scientific validation as an antioxidant powerhouse. Among the most recent findings:
- After consuming a blend of acai polyphenols, researchers recorded a three-fold increase in antioxidant capacity in the blood of healthy human volunteers.12
- Antioxidants found specifically in freeze-dried acai extract have been shown to enter human cells in a fully functional form and effectively neutralize free radicals at very low doses.13
- Similarly, freeze-dried acai extract has demonstrated unrivalled scavenging capacity against two of the most damaging reactive oxygen species, the superoxide and peroxyl radicals.14
In this article, you will learn how the antioxidant potency of acai and other foods is assessed, using a measurement known as oxygen radical absorbance capacity, or ORAC.15,16 You will find out the most recent research indicating that the full polyphenolic profile of acai affords optimal antioxidant protection. You will also gain insight into the specific health benefits of acai and similarly potent fruits and vegetables--and their unrivalled power to combat free radical damage and the killer diseases of aging.Assessing Antioxidant Potency
The standard index for determining the antioxidant value of various organic compounds is known as oxygen radical absorbance capacity, or ORAC.17-19 Developed by scientists at the USDA Human Nutrition Research Center on Aging at Tufts, the ORAC test is considered one of the most sensitive and reliable methods for measuring the ability of antioxidants to absorb free radicals. While other analytic methodologies may be used, ORAC is often considered preferable because of its biological relevance to antioxidant action in vivo (in living organisms).20 It measures both the degree and speed with which a certain food inhibits the action of an oxidizing agent, then integrates these two measurements into a single value, producing an accurate assessment of different types of antioxidants of different strengths.21,22
The ORAC value of a given food is proportional to its polyphenol content. Fruits and vegetables with a higher ORAC value--or richer color--have been shown to suppress free radicals more effectively than lightly pigmented foods.23 Scientists at the US Department of Agriculture advise that we ingest foods equivalent to 3,000-5,000 ORAC units per day in order to maintain optimal antioxidant protection in bodily tissues and plasma 24,25--a number that may be too low.ORAC: Top-Ranked Antioxidant Foods
The numerical values above indicate ORAC units per 100 grams (about 3.5 ounces).26-29Unrivalled Free Radical Defense
|Red bell pepper
The acai (Euterpe oleraceae Mart.) is a species of palm tree indigenous to the area surrounding the Amazon in South America. Its berries resemble grapes and ripen seasonally in similar fashion, progressing from green to a deep purple color.30 They have long served as a critical nutritional source for the native peoples of Central and South America. Modern scientific analysis revealed that the acai berry's complete polyphenolic profile boasts a formidable array of beneficial compounds, including polyunsaturated and monounsaturated fatty acids (11.1% and 60.2%, respectively), along with 19 health-promoting amino acids.31
Celebrated in traditional cultures for its life-sustaining power, the magnitude of acai's antioxidant capability only recently emerged in scientific studies.32 acai powerfully counteracts several of the most destructive reactive oxygen species (ROS), or free radicals. In freeze-dried form, it has been shown to effectively inhibit the ROS superoxide in assays, and excels against the peroxyl radical in particular, with the highest reported total ORAC score of any fruit or vegetable.33 acai was also found to be active against the peroxynitrite and hydroxyl radicals in ORAC assays.34,35 It has also been identified recently as a potent COX-1 and COX-2 inhibitor, which may give it the ability to provide relief from pain and inflammation.36
A study designed to evaluate total free radical scavenging capacity among various antioxidant foods revealed that when compared to common European fruit and vegetable juices, all the acai samples studied ranked in the top class of peroxyl radical scavengers.37 The authors found the samples to be so high in antioxidant capacity that the numbers could only be estimated. Another study found that human plasma antioxidant activity is significantly increased after the consumption of acai pulp and juice, observing individual increases in plasma antioxidant activity of up to 2.3-3-fold, respectively.38
Its potent antioxidant properties and highly beneficial polyphenolic profile endow acai with a singular ability to combat cellular aging and oxidative damage. The latest research reveals the potential for significant beneficial effects on longevity and incidence of chronic disease. A study on the life span and survival of Drosophila melanogaster flies found that dietary supplementation of 2% acai increased the life span of females fed a high-fat diet by approximately 20%, compared to controls fed a high-fat diet without acai.39 acai was noted to promote the activation of important stress-response pathways, alleviate the oxidative stress of aging, and protect against the negative effects of dietary fats.40,41
What You Need to Know: Scientific Validation for acai
- Every cell in the human body withstands an estimated 10,000 individual strikes by free radicals each day, a leading factor in aging and degenerative disease onset.
- Although promoted commercially for years as a nutritionally dense food, the deep purple acai berry has only recently gained compelling scientific validation.
- In a recent clinical study, a blend of complete acai polyphenols increased antioxidant capacity three-fold in the blood of healthy human volunteers.
- Antioxidants found specifically in freeze-dried acai extract have been shown to enter human cells in a fully functional form and effectively neutralize free radicals at very low doses.
- Freeze-dried acai extract is also extraordinarily effective against the most damaging reactive oxygen species, the superoxide and peroxyl radicals.
- Scientific research suggests that together with similarly pigmented foods rich in anthocyanins (blueberries, black currant, and raspberries), acai may serve as a frontline defense against multiple diseases of aging.
Evidence is also building for acai as a major cancer fighter. Polyphenolic mixtures of acai pulp and oil extracts inhibited the proliferation of human colon cancer cells in the lab by up to 90.7%42 and a study on human leukemia cells found acai polyphenols reduced cell proliferation from 56-86%.43 acai pulp was also found to be protective when administered to mice prior to the chemotherapeutic drug doxorubicin.44
Acai is also emerging as a major cardiovascular protector.45 In one study, acai extract induced long-lasting endothelium-dependent vasodilation (relaxing of the arterial wall) in the abdominal vascular tissue of rats.46 Supplementation with acai berries has also been shown to reduce total and non-HDL cholesterol in animals with experimentally induced high cholesterol.47
Acai's high antioxidant capacity also benefits brain function, with potential implications for the treatment of neurological disorders, including Alzheimer's disease and Parkinson's disease. Research has shown that pre-treatment of brain tissue from the cerebral cortex, cerebellum, and hippocampus with acai decreased ROS-induced damage of lipids and proteins in all brain tissues tested.48Anthocyanins: Broad-Spectrum Disease Protection
The most powerful antioxidant berries to emerge in recent studies contain a class of polyphenols (plant-based compounds) known as anthocyanins. These nutrients produce the deep red, blue, and purple pigments found throughout the plant kingdom.
Fruits and vegetables bearing these colors--blueberries, cranberries, pomegranates, black currants, beets, and acai--are especially rich in anthocyanins. Although present only in minute quantities, they are readily absorbed into the blood upon ingestion, where they initiate a physiological response in the body that quells free radical activity.
The most up-to-date research indicates that anthocyanins confer a broad array of health benefits, including:
- inhibiting cancer cell growth and inducing apoptosis (programmed cell death) in several cancer cell lines49-52
- reducing the risk of cardiovascular disease53-55
- enhancing glucose tolerance and lipid profiles56,57
- improving eye function58,59
- limiting cellular oxidative DNA damage.60,61
An 8-week, randomized, placebo-controlled study published this year confirmed not only that they are highly bioavailable--they can also significantly increase levels of other beneficial polyphenols in the blood.62
In addition to acai, anthocyanins are distributed widely among nature's most brightly colored fruits and vegetables.Other Beneficial Pigmented PlantsBlueberry
Blueberries have been shown to enhance cognitive performance, and are abundant in polyphenols that can cross the blood-brain barrier and localize in regions critical to learning and memory.63 Blueberries protect the myocardium from ischemic damage and prevent post-myocardial infarction heart failure.64 They have also been found to improve insulin resistance and thus glucose control in pre-clinical models.65 Taken together with probiotics, they may help counteract colitis (inflammation of the large intestine).66Bilberry
This relative of the blueberry may provide a frontline defense against cardiovascular disease. Researchers have found that bilberry significantly inhibits angiotensin-converting enzyme, or ACE, which contributes to hypertension by promoting dangerous narrowing of the arteries (vasoconstriction).67 Bilberries enhance short-term memory in animal models, suggesting they may have potential to help ward off Alzheimer's disease.68 Like many anthocyanin-rich foods, bilberries also inhibit proliferation of breast cancer cells and induce apoptosis in animal models.69 They improve insulin sensitivity, helping to prevent diabetes.70 Bilberry extract helps to upregulate enzymes that defend against ocular oxidative stress as well, suggesting it may be beneficial for protecting the eyes against age-related disorders, like macular degeneration.71Black Currant
Black currant boasts potent anti-viral activity72 and has been shown to relax the aorta by enhancing the synthesis of nitric oxide.73 Black currant also reduced the oxidative stress induced by exercise and may enhance immune responsiveness to pathogens.74 One study found that black currant extract improved volunteers' ability to adapt to the symptoms of tired eyes.75 Black currant has also been shown to stop the growth of certain harmful bacteria.76
Blueberries have been shown to enhance cognitive performance and are abundant in polyphenols... critical to learning and memory.Cranberry
Cranberries are probably best known for the support they provide the urinary tract, by inhibiting the adherence of E. coli to the urethra and bladder.77 They're also proven fighters of oxidative stress. An 8-week, double-blind, placebo-controlled trial involving 65 healthy women found that 1,200 mg of cranberry extract per day prompted a significant decrease in serum levels of advanced oxidation protein products--a key measure of oxidative stress.78 Cranberries also display anti-proliferative activity against several types of cancer in vitro and in vivo, including gastric cancer79 and esophageal adenocarcinoma.80 They may also help to fend off ulcers by preventing Helicobacter pylori, the bacterium which causes peptic ulcers, from adhering to the stomach lining.81,82Elderberry
Like black currant, elderberry is a natural anti-viral that shows promise in protecting against both seasonal and H1N1 swine influenza. Elderberry anthocyanins have been found to bind to H1N1 and block the ability of the virus to infect host cells. Researchers have favorably compared its activity to that of oseltamivir (Tamiflu®).83 A randomized, double-blind, placebo-controlled study on a standardized elderberry product found that it reduced the duration of the flu symptoms to just 3-4 days.84 The study also showed it to be effective against 10 different strains of influenza. Elderberry also reduces lipid peroxides, neutralizes lipid peroxyl radicals, inhibits LDL oxidation,85 and offers significant protection to endothelial cells against oxidative stress.86Pomegranate
Pomegranate provides broad-spectrum benefits across many physiological systems. Extracts of pomegranate have shown promise in reducing the potential for metastasis in breast cancer.87 They initiate programmed cell death and inhibit the proliferation of prostate, lung, colon, and other cancers.88-91 The fruit has also been shown to reduce inflammation in colitis92 and suppress inflammation and joint damage in rheumatoid arthritis,93 not to mention its status as a known cardiovascular tonic.94Other Beneficial Pigmented Plants
A rich variety of additional brightly pigmented foods afford similar health benefits.
Raspberries protect against DNA damage95 in HT-29 colon cancer cells, and inhibit HT-115 colon cancer invasion, in vitro.96 In combination with other berry extracts, raspberry extracts have shown efficacy against oral, breast, and prostate cancers in the lab.97 The antioxidant capacity of aronia or chokeberries have yielded some of the highest ORAC values recorded;98 drinking the juice of these berries reduces exercise-induced oxidative damage to red blood cells99 and in one study, a cholesterol-lowering effect was observed in animals with experimentally induced high cholesterol.100 Aronia has also been found to decrease lipid peroxidation and oxidative stress.101
Grapes and grape seeds have been shown to inhibit colon cancer cell invasion102 and decrease LDL oxidation and platelet aggregation, among other cardioprotective activities.103 Grapes have also been found to extend the life span of fruit flies, and may help combat Parkinson's and other neurodegenerative diseases.104
Strawberry extracts have been shown to inhibit the growth of oral, colon, and prostate cancer cells,105 improve lipid profiles and peroxidation106 and lower the risk of coronary artery disease.107
Blackberries have shown themselves to be extremely beneficial in the management of inflammation, suppressing pro-inflammatory cytokines in animal models. Blackberry extracts also show potential in inhibiting the growth of human colon cancer cells in the laboratory, suggesting a potential role in cancer prevention.108
Cherries have been found to reduce blood lipid abnormalities109 and glucose intolerance and abdominal obesity in mice.110,111 Tart cherries have been found effective in suppressing inflammation-induced pain.112
The benefits of anthocyanins are not limited to fruits: studies have shown that the black soybean shows promise in fighting colon cancer113 and insulin resistance,114 and promotes wound healing in skin cells and reduces inflammation in endothelial cells.115
Purple corn possesses anti-mutagenic effects, reducing expression of genes involved in proliferation of tumor cells.116,117Summary
Each day, every cell in the human body withstands 10,000 individual strikes by free radicals, a leading factor in aging and degenerative disease onset. In the search for optimal defense against free radicals, scientists have focused intensely on berry extracts for their potent antioxidant capacity. Although promoted commercially for years as a nutritionally dense food, the deep purple acai berry has only recently gained compelling scientific validation. In a recent clinical study, a blend of complete acai polyphenols increased antioxidant capacity three-fold in the blood of healthy human volunteers. Antioxidants found specifically in freeze-dried acai extract have been shown to enter human cells in a fully functional form and effectively neutralize free radicals at very low doses. Freeze-dried acai extract is also extraordinarily effective against the most damaging reactive oxygen species, the superoxide and peroxyl radicals. Scientific research suggests that together with similarly pigmented foods rich in anthocyanins (blueberries, black currant, and raspberries), acai may serve as a frontline defense against multiple diseases of aging.References
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