Acai - Nature's Energy Fruit
Table of Contents:
"It may seem odd to start this list of superfoods with one you’ve likely never even heard of. But studies have shown that this little berry is one of the most nutritious and powerful foods in the world! Acai (ah-sigh-ee) is the high-energy berry of a special Amazon palm tree. Harvested in the rainforests of Brazil, acai tastes like a vibrant blend of berries and chocolate. Hidden within its royal purple pigment is the magic that makes it nature's perfect energy fruit. Acai is packed full of antioxidants, amino acids and essential fatty acids. Although acai may not be available in your local supermarket, you can find it in several health food and gourmet stores (often in juice form)….
Acai pulp contains:
A remarkable concentration of antioxidants that help combat premature aging, with 10 times more antioxidants than red grapes and 10 to 30 times the anthocyanins of red wine.
A synergy of monounsaturated (healthy) fats, dietary fiber and phytosterols to help promote cardiovascular and digestive health. An almost perfect essential amino acid complex in conjunction with valuable trace minerals, vital to proper muscle contraction and regeneration.
The fatty acid content in acai resembles that of olive oil, and is rich in monounsaturated oleic acid. Oleic acid is important for a number of reasons.
It helps omega-3 fish oils penetrate the cell membrane; together they help make cell membranes more supple. By keeping the cell membrane supple, all hormones, neurotransmitter and insulin receptors function more efficiently. This is particularly important because high insulin levels create an inflammatory state, and we know, inflammation causes aging." - N.V. Perricone, M.D.
The dense pigmentation of acai has led to several experimental studies of its anthocyanins, a group of polyphenols that give the deep color to fruits and vegetables and are high in antioxidant value. A recent study using a standardized freeze-dried acai fruit pulp and skin powder found the total anthocyanin levels to be 319 mg per 100 grams (Schauss et al., 2006a). Cyanidin 3-glucoside and cyanidin 3-rutinoside were the major anthocyanins determined in this study as well several other studies including one by Lichtenthaler in 2005.
Twelve other flavonoid-like compounds were additionally found in the Schauss et al. 2006a study, including homoorientin, orientin, taxifolin deoxyhexose, isovitexin and scoparin, as well as several unknown flavonoids. Proanthocyanidins, another group of polyphenolic compounds high in antioxidant value, totaled 1,289 mg per 100 grams of the freeze-dried pulp/skin powder, with a profile similar to that of blueberries (Schauss et al., 2006a). Resveratrol was additionally found to be present in acai in this study, although at low levels of 1.1 microgram per gram.
A number of studies have measured the antioxidant strength of acai. Unfortunately, the sources of acai and preparations (e.g., whole fruit, juice, extract or soluble powder) for reporting the results vary. A recent report using a standardized oxygen radical absorbance capacity or ORAC analysis on a freeze-dried acai powder found that this powder showed an extremely high antioxidant effect against peroxyl radical. In fact, it had the highest total antioxidant level (1027 micromol TE/g) of any food tested by ORAC to date. This includes a high lipophilic antioxidant content when compared to other berries. The ORAC value for this freeze-dried powder was significantly higher than when other methods of drying the fruit were tested (Schauss, 2006c).
The freeze-dried acai powder also showed very high activity against superoxide, with a SOD assay level of 1614 units/g. Superoxide is thought to be the initial producer of other more potent reactive oxygen species, and thus protection against it is very important as a first line of defense for the body. Antioxidant activity against both peroxynitrite and hydroxyl radicals was also observed, although effects were milder than that seen against peroxyl radical and superoxide. Additionally, antioxidant molecules from the freeze-dried powder were shown to actually enter freshly obtained human neutrophils and inhibit oxidation induced by hydrogen peroxide, even at very low concentrations of the acai powder including 0.1 part per trillion (Schauss et al., 2006b). A previous report using a total oxygen scavenging capacity assay also found that acai has extremely high antioxidant effects against peroxyl radical, as well as a high capacity against peroxynitrite, and a moderate capacity against hydroxyl radical when compared with other fruit and vegetable juices. (Lichtenthäler et al, 2005)
Interestingly, the Lichtenthäler et al. study determined that only 10% of acai's high antioxidant effects could be explained by its anthocyanin content. Schauss et al. similarly found that that ratio of the hydrophilic ORAC levels to the total phenolics in the freeze-dried fruit was 50, which is quite a bit higher than the average fruit and vegetable ratio of 10. This suggests that either there are other unknown antioxidants present contributing to this high antioxidant activity and/or the antioxidants that acai contains are especially strong.
Schauss et al. (2006b) also utilized the "Total Antioxidant" or TAO assay to differentiate the "fast-acting" (measured at 30 seconds) and "slow-acting" (measured at 30 minutes) antioxidant levels present in freeze-dried powder. Acai was found to have a higher "slow-acting" antioxidant components, suggesting a more sustained antioxidant effect compared to "fast-acting" components.
Although it is unknown exactly how these in vitro antioxidant levels will translate into health potentials for humans in vivo, it is likely that acai fruit imparts health benefits associated with consumption of foods high in antioxidants, such as reduced risk or prevention of chronic and oxidative stress related disorders.
Antioxidant values of the seeds of the acai fruit have also been reported (Rodrigues, 2006). Similarly to the berries, the antioxidant capacity of the seeds were strongest against peroxyl radicals, at a concentration in the same order of magnitude as the berries. The seeds had a stronger antioxidant effect than the berries for peroxynitrite and hydroxyl radicals, although still less than its effects against peroxyl radical. The results of this study were not linear based on the concentration of the seeds that were used. The authors suggest the future use of the seeds (a by-product of juice making) for antioxidant benefits such as prolonging shelf-life of foods.
Acai, in the form of a specific freeze-dried acai fruit pulp, has been shown to have mild ability to inhibit cyclooxygenase enzymes COX-1 and COX-2, with more effect on COX-1 (Schauss et al., 2006b). These enzymes are important in both acute and chronic inflammation, and are targeted by many of the anti-inflammatory medications (NSAIDs). Additionally, lower concentrations (but not higher concentrations) of the freeze-dried pulp were found to be slightly stimulating to macrophages in vitro. Macrophages are white blood cells that are an important part of the immune system of the body. Also in macrophages, freeze-dried acai pulp was found to inhibit the production of nitric oxide that had been induced by the potent inflammatory inducer lipopolysaccharide (LPS), which is part of the cell membrane of certain bacteria (Schauss et al. 2006b). This effect increased as the concentration of the acai increased. This suggests again the potential for an anti-inflammatory effect of acai, although requires more research.
In 2006, a study performed at the University of Florida showed that acai fractions containing polyphenolics could reduce proliferation of HL-60 leukemia cells in vitro. This was most likely due to increased rapid cell death (apoptosis) as fractions were also found to activate caspase-3 (an enzyme important in apoptosis) which was inversely correlated to cell death. (Pozo-Insfran et al., 2006). This is a very preliminary study, but indicates a need for more research on the possible anti-cancer effects of acai.
Due to its deep pigmentation, orally-administered acai has been tested as a contrast agent for magnetic resonance imaging of the gastrointestinal system (Cordova-Fraga et al., 2004). Its anthocyanins have been characterized for stability as a natural food coloring agent (Del Pozo-Insfran et al., 2004).