Imported Fruits: Drink Their Juices?
Imported Fruits: Drink Their Juices?
By David Kiefer, MD. Dr. Kiefer is Clinical Instructor, Family Medicine, University of Washington, Seattle; Clinical Assistant Professor of Medicine, University of Arizona, Tucson; and Adjunct Faculty, Bastyr University, Seattle; he reports no financial relationship to this field of study.
In the popular press, there has been a recent focus on "superfoods," or foods that contain high levels of nutrients that some people feel have the best evidence for the prevention or treatment of various medical conditions.1,2 Examples are avocado, blueberries, dark chocolate, oats, olive oil, salmon, and yogurt. Along the same vein, juices from imported, often tropical, fruits are mentioned as being "healthy" and are now common on the shelves of health foods stores, pharmacies, and most of our refrigerators; for example, recent sales show double-digit growth in juices from açaí (pronounced "ah-sai-EE"), mangosteen, and pomegranate.3 In most cases, these fruits have a long history of traditional use as foods and medicines, and laboratory and clinical trials are starting to elicit their mechanisms of action, clinical uses, and other effects. This review will detail some of this research, helping health care practitioners guide their patients' choice of refreshing drinks.
History, Traditional Use, and Botany
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Each of these plants has a rich history of traditional use as foods and medicines (see Table, above). For example, açaí is a palm widely distributed in northern South America, especially important economically in the Brazilian state of Pará, and considered abundant in eastern Amazonian estuary floodplains.4,5 The trees produce a dark, purple-colored fruit, yielding a viscous juice for use in energy drinks, jellies, ice cream, and to mix with other juices4; açaí is also mentioned as a treatment for diarrhea.6 The immature fruits are green, though if they remain green in the mature state the fruits are called white açaí. The pulp is approximately 50% lipid and 10% protein, and is said to taste like a mix of beets and carrots.5 One example of an açaí juice blend studied in a recent clinical trial is Mona Vie Active®.7
Another "exotic" fruit is mangosteen. Mangosteen, locally known in Thai as mangkhut, is a tree thought to be native to Indonesia or Southeast Asia, and has been cultivated for centuries in tropical areas such as Indonesia, Malaysia, Thailand, and the Philippines.8,9 It is considered by some to have the best tasting fruit in the world. The fruit, roughly the size of a tangerine, contains a white inner pulp that is divided into 4-8 segments, and a non-edible, tough, bitter pericarp (or peel, rind, or fruit hull) that contains a yellow resin with physiologically active phytochemicals, xanthones.8 The pericarp has been used for treating cough, cystitis, diarrhea and other intestinal ailments, eczema, fever, pruritis, and various skin conditions, whereas the leaves have traditionally been used in teas and for diarrhea, dysentery, fever, and thrush, and the bark can be used for genitourinary complaints and stomatitis.8
The pomegranate is a small tree or large shrub originating from the Middle East, but now found throughout the Mediterranean, and in China, India, Mexico, and the American Southwest.10 The pomegranate fruit, botanically considered a berry, contains, by weight, 3% seeds (20% of which is oil), 30% juice, and the rest pericarp, including the inner network of membranes.10 The pomegranate plant is a prominent part of many religions and societies, dating back centuries, and its fruit, bark, roots, and flowers have had a wide variety of medical uses, including for diarrhea, parasites, apthous ulcers, contraception, HIV, allergies, cardiovascular protection, and as a "blood tonic."10
Pharmacology and Mechanism of Action
The phytochemical constituents of these plants have mostly been determined, and numerous in vitro and animal studies have begun to elucidate their mechanism of action. An analysis of açaí pulp showed the presence of anthocyanins such as cyanidin and pelargonidin, and polyphenols such as ferulic acid, catechin, epicatechin, gallic acid, and homoorientin.4,11,12 Açaí oil is also being studied; it contains 60% oleic acid, 22% palmitic acid, 12% linoleic acid, and other fatty acids in trace amounts, as well as numerous phenolic compounds, such as procyanidins and phenolic acids, but not anthocyanins.11,13
Most mechanistic studies have focused on the anticancer and antioxidant effects of açaí. For example, one analysis using the total oxidant scavenging capacity (TOSC) placed açaí in the top class of oxidant-scavenging juices, except for white açaí which was in the lowest class along with tomato and sauerkraut juices; the researchers attributed this high TOSC capacity to as-yet-unidentified compounds other than the known anthocyanins.5 Another research group using a different antioxidant assay (Trolox equivalents per milliliter) found the antioxidant level of açaí was comparable to cranberries, and approximately double the levels for blueberries, raspberries, strawberries, blackberries, and muscadine grape juice.4 Methanol extracts of the seeds appear to be the most effective antioxidants, partially due to the oligomeric procyanidins,14 and methanol extracts of the fruit also show antioxidant effects.6
With respect to cancer, an in vitro study on a human leukemic cell line showed that the polyphenolics in açaí induced apoptosis in a dose-dependent and time-dependent fashion.15 In addition, in vitro inhibition of human colon carcinoma cell growth was observed for both the pulp and phytochemically enriched açaí oil, though more so for the oil, probably due to different concentrations of the relevant phytochemicals.11
Finally, extracts (hydro-alcoholic more so than water) of açaí fruit stone (or "pit") and skin causes a dose-dependent vasodilation of rat mesenteric vascular bed, possibly through an antioxidant effect that increases the bioavailability of nitric oxide (NO).12
Some of these same themes continue with mangosteen. Mangosteen pericarp contains a variety of compounds, including the xanthones alpha-, beta-, and gamma-mangostin, methoxy-beta-mangostin, tannin, garcinone, gartanin, polyphenolic acids such as phenols, and chrysanthemin.8 Mangosteen pericarp extracts have shown anti-inflammatory and antioxidant effects, inhibitory effects against skin and gastrointestinal bacteria, and antitumor effects.9 The xanthones have been shown to have antibacterial, antifungal, and antitumor activity, and cancer cell toxicity effects against human leukemia and colon cancer cell lines in vitro, mainly due to apoptosis.8,16
Methanol extracts of mangosteen pericarp have a dose-dependent inhibition of breast cancer cells in vitro comparable to the controls quercetin and paclitaxel, and there are indications of an apoptotic effect; morphological changes in those cells at several concentrations; and, a suppression of intracellular reactive oxygen species, consistent with an antioxidant effect.9 Alpha- and gamma-mangostin have anti-inflammatory activity in some in vitro models.17 When alpha- and gamma-mangostin were studied in an in vitro human adipocyte model, they were found to decrease the induction of inflammatory genes related to insulin resistance.17 In vitro and in vivo models show anti-inflammatory effects of gamma-mangostins greater than alpha-mangostins, via NO and prostaglandin-E2 (PGE2), but not via inhibition of the COX-2 enzyme system.16 In another in vitro study, however, a mangosteen extract was found to have neither antitumor nor antihelmintic effects.18 Researchers have found that mangosteen pericarp has an antioxidant effect in in vitro neuron models.19 Finally, an in vitro study showed potent anti-inflammatory effect for the pericarp extract, as well as the alpha-mangostin and gamma-mangostin fractions, related to inhibition of NO and PGE2 release, as well as TNF-alpha and IL-4 levels.20 Inhibitory effects against acne-causing skin bacteria (Propionibacterium acnes, Staphylococcus epidermidis) were also identified.21
Pomegranate juice contains the antioxidant flavonoids anthocyanins and proanthocyanidins, which provide its dark red color, as well as pentose glycosides such as malvidine and pentunidin, catechins and epicatechins, as in green tea and dark chocolate, and quercetin; the pericarp also contains anthocyanins, in addition to tannins.10 There are numerous in vitro trials documenting the antitumor effects of extracts from different parts of the pomegranate; apparent mechanisms and actions include increased apoptosis, decreased inflammation, decreased metastasis, and decreased drug resistance. The anti-inflammatory and antioxidant effects of pomegranate juice and its individual components have been well-established, affecting several different enzyme systems, including lipoxygenase and cyclooxygenase.10,22 Pomegranate juice has been shown to have in vitro antiplatelet activity,23 and anti-anxiety effects in mice.24
With respect to antioxidant effects there are many assays, and although the oxygen radical absorbance capacity (ORAC) is most commonly mentioned in the literature, there are others, such as TEAC, FRAP, and DPPH, that can estimate a given compound's antioxidant effect. One group compared juices by creating a composite index score (100 = best) using seven antioxidant tests, and found pomegranate juice to score 95.8, red wine 68-72, Concord grape juice 57-70, açaí juice 44-54, iced green tea, 17-29, apple juice 14-15, and iced white tea 5-24.25 Other groups found that purple (Concord) grape juice had the highest level of phenolics and antioxidant effect (using ORAC and FRAP tests), followed by apple juice, pomegranate juice, and cranberry juice drink.26
Clinical Trials
Açaí and mangosteen have limited human research associated with them, whereas pomegranate juice has been more extensively studied. A study of 7 mL/kg of clarified açaí juice as a one-time dose in 12 human subjects showed plasma, but not urine, antioxidant effects after the ingestion of both açaí pulp and juice (but pulp more than juice) when compared to a control beverage.27 The researchers also demonstrated that açaí anthocyanins are bioavailable. For mangosteen, an extract of alpha- and gamma-mangostin (150 mg daily for 7 days) was found to upregulate natural killer cell activity in a pilot human study.8
Some examples of the type of clinical research performed on pomegranate juice follows:
Pomegranate juice (250 mL daily for 4 weeks) was administered to 13 elderly subjects and, compared to a control group consuming apple juice, improved antioxidant function in the pomegranate group was found.28
Another study of 30 people with type 2 diabetes compared 10 men and 10 postmenopausal women ingesting 50 mL of pomegranate juice (from a variety called Wonderful) daily for 4 weeks with 10 men ingesting 5 mL of a pomegranate polyphenol extract daily for 6 weeks.29 When compared to baseline levels, all groups demonstrated serum antioxidant effects and an increased affinity of paraoxonase-1 with HDL-cholesterol, two effects which could be of significance in decreasing atherosclerosis in diabetics. In another study, 10 people with type 2 diabetes drank 50 mL of pomegranate juice daily for 3 months, and baseline and follow-up laboratory analyses were done, comparing the results to 10 healthy subjects who also drank the same amount of pomegranate juice.30 The baseline labs were predictable, with the diabetes group showing elevated triglycerides, lower HDL-cholesterol, increased hemoglobin-A1c, and elevated lipid peroxides, a measure of serum oxidative status. After the pomegranate treatment, there was no change in hemoglobin-A1c (an interesting result given that pomegranate juice contains 10% total sugars), a decrease in lipid peroxidation, a decrease in in vitro oxidative status, as well as a decrease in oxidized LDL-cholesterol uptake by macrophages, which the authors interpret as showing an anti-atherogenic effect.
Other clinical trials have examined the effect of pomegranate on hypertension and atherosclerosis, documenting such results as lower systolic blood pressure and decreased thickness of the carotid artery.22 Pomegranate juice in higher doses (240 mL daily) may decrease myocardial ischemia, as demonstrated in a 3-month, randomized, placebo-controlled trial.31
Other Berries
There are many other berries containing antioxidant phytochemicals similar in structure and physiological effect as the three fruits reviewed in this article. Native to North America, of course, are blueberries, cranberries, blackberries, and strawberries, among others, which have various polyphenols such as anthocyanins.32 Also readily available in many grocery stores, health foods stores, and on-line, are juices from the fruits of noni (Morinda citrofolia), goji (Lycium chinense), and a fermented tea beverage purportedly high in B vitamins, kombucha.
Dose and Administration
The plants are often recommended as juices, occasionally a single juice extract, but more often as a mixture with other juices. It is not immediately obvious what an adequate daily dose of these juices should be. If there were large epidemiological studies available, it would be possible to extrapolate from populations that ingest a given amount of juice on a regular basis and possibly identify an improvement in disease outcomes, and make a recommendation to a given patient or patient population; these data do not exist at this point. Some indication of possible dosing comes from the clinical trials as mentioned above. For example, in clinical trials pomegranate juices have been dosed at approximately 50-240 mL (4 Tbsp to 1 cup) daily.
Adverse Effects
Polyphenol-enriched extracts of pomegranate juice have been found to be safe in humans and animals, but the lack of definitive data makes it difficult to comment on the safety of pomegranate juice in high doses or in specific clinical situations.22 The same can be said for açaí and mangosteen. For example, researchers and experts have debated in the medical literature the pros and cons of antioxidant ingestion during cancer treatment; until this issue is resolved, caution, or better yet, avoidance of strong antioxidant foods and supplements is recommended in this clinical setting.
Conclusion
Açaí, mangosteen, and pomegranate are each plants with a rich history of traditional use as both foods and medicines. The most commonly used parts are the fruit pulp for açaí, the fruit rind (pericarp) for mangosteen, and the fruit juice of pomegranate. All of these plants contain phytochemicals that have shown primarily antioxidant, but also anti-inflammatory, and antitumor effects: anthocyanins (açaí, pomegranate), catechins (açaí, pomegranate), xanthones (mangosteen), and polyphenols (açaí, mangosteen, pomegranate). There is only one clinical trial each for açaí and mangosteen, demonstrating antioxidant and immune system effects, respectively. There are many, mostly small, clinical trials for pomegranate juice, showing serum antioxidant effects, and improvements in cardiovascular parameters.
Recommendation
There is an allure of exotic fruits and the possibility of improving certain medical conditions with their ingestion. For açaí, mangosteen, and pomegranate, phytochemical analyses, in vitro studies, and some clinical trials (the latter primarily for pomegranate) support antioxidant and other effects that may correlate with improvements in some disease outcomes. The ideal doses, possible side effects, and identification of people most likely to benefit from specified juice ingestion, if any, have yet to be determined. It probably isn't worth spending the significant dollars these juices usually command when there are other fruits and juices that have been better studied. Perhaps future data will provide more to recommend açaí, mangosteen, and pomegranate than antioxidant potential, but until that time there is little clinical reason to use them, with the possible exception of pomegranate juice.
References
1. Seliger S. "Superfoods" everyone needs. Available at: www.webmd.com/diet/features/superfoods-everyone-needs. Accessed July 7, 2009.
2. What is "Super Food"? Available at: www.superfoodsrx.com/superfoods. Accessed July 7, 2009.
3. Cavaliere C, et al. Herbal supplement sales experience slight increase in 2008. HerbalGram 2009;82:58-61.
4. Del Pozo-Insfran D, et al. Phytochemical composition and pigment stability of Açai (Euterpe oleracea Mart.). J Agric Food Chem 2004;52:1539-1545.
5. Lichtenthäler R, et al. Total oxidant scavenging capacities of Euterpe oleracea Mart. (Açaí) fruits. Int J Food Sci Nutr 2005;56:53-64.
6. Chin YW, et al. Lignans and other constituents of the fruits of Euterpe oleracea (Açaí) with antioxidant and cytoprotective activities. J Agric Food Chem 2008;56: 7759-7764.
7. Jensen GS, et al. In vitro and in vivo antioxidant and anti-inflammatory capacities of an antioxidant-rich fruit and berry juice blend. Results of a pilot and randomized, double-blinded, placebo-controlled, crossover study. J Agric Food Chem 2008;56:8326-8333.
8. Akao Y, et al. Anti-cancer effects of xanthones from pericarps of mangosteen. Int J Mol Sci 2008;9:355-370
9. Moongkarndi P, et al. Antiproliferation, antioxidation and induction of apoptosis by Garcinia mangostana (mangosteen) on SKBR3 human breast cancer cell line. J Ethno-pharmacol 2004;90:161-166.
10. Lansky EP, Newman RA. Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. J Ethnopharmacol 2007; 109;177-206.
11. Pacheco-Palencia LA, et al. Absorption and biological activity of phytochemical-rich extracts from açai (Euterpe oleracea Mart.) pulp and oil in vitro. J Agric Food Chem 2008;56:3593-3600.
12. Rocha AP, et al. Endothelium-dependent vasodilator effect of Euterpe oleracea Mart. (Açaí) extracts in mesenteric vascular bed of the rat. Vascul Pharmacol 2007;46: 97-104.
13. Pacheco-Palencia LA, et al. Chemical composition, antioxidant properties, and thermal stability of a phytochemical enriched oil from Açaí (Euterpe oleracea Mart.). J Agric Food Chem 2008;56:4631-4636.
14. Rodrigues RB, et al. Total oxidant scavenging capacity of Euterpe oleracea Mart. (açaí) seeds and identification of their polyphenolic compounds. J Agric Food Chem 2006; 54:4162-4167.
15. Del Pozo-Insfran D, et al. Açai (Euterpe oleracea Mart.) polyphenolics in their glycoside and aglycone forms induce apoptosis of HL-60 leukemia cells. J Agric Food Chem 2006;54:1222-1229.
16. Chen LG, et al. Anti-inflammatory activity of mangostins from Garcinia mangostana. Food Chem Toxicol 2008;46: 688-693.
17. Bumrungpert A, et al. Xanthones from mangosteen prevent lipopolysaccharide-mediated inflammation and insulin resistance in primary cultures of human adipocytes. J Nutr 2009;139:1185-1191.
18. Atjanasuppat K, et al. In vitro screening for anthelmintic and antitumour activity of ethnomedicinal plants from Thailand. J Ethnopharmacol 2009;123:475-482.
19. Weecharangsan W, et al. Antioxidative and neuroprotective activities of extracts from the fruit hull of mangosteen (Garcinia mangostana Linn.). Med Princ Pract 2006;15: 281-287.
20. Tewtrakul S, et al. Effects of compounds from Garcinia mangostana on inflammatory mediators in RAW264.7 macrophage cells. J Ethnopharmacol 2009;121:379-382.
21. Chomnawang MT, et al. Antimicrobial effects of Thai medicinal plants against acne-inducing bacteria. J Ethnopharmacol 2005;101:330-333.
22. Basu A, Penugonda K. Pomegranate juice: A heart-healthy fruit juice. Nutr Rev 2009;67:49-56.
23. Mattiello T, et al. Effects of pomegranate juice and extract polyphenols on platelet function. J Med Food 2009;12: 334-339.
24. Kumar S, et al. Central nervous system activity of acute administration of ethanol extract of Punica granatum L. seeds in mice. Indian J Exp Biol 2008;46:811-816.
25. Seeram NP, et al. Comparison of antioxidant potency of commonly consume polyphenol-rich beverages in the United States. J Agric Food Chem 2008;56:1415-1422.
26. Mullen W, et al. Evaluation of phenolic compounds in commercial fruit juices and fruit drinks. J Agric Food Chem 2007;55:3148-3157.
27. Mertens-Talcott SU, et al. Pharmacokinetics of anthocyanins and antioxidant effects after the consumption of anthocyanin-rich açaí juice and pulp (Euterpe oleracea Mart.) in human healthy volunteers. J Agric Food Chem 2008;56:7796-7802.
28. Guo C, et al. Pomegranate juice is potentially better than apple juice in improving antioxidant function in elderly subjects. Nutr Res 2008;28:72-77.
29. Rock W, et al. Consumption of wonderful variety pomegranate juice and extract by diabetic patients increases paraoxonase 1 association with high-density lipoprotein and stimulates its catalytic activities. J Agric Food Chem 2008;56:8704-8713.
30. Rosenblat M, et al. Anti-oxidative effects of pomegranate juice (PJ) consumption by diabetic patients on serum and on macrophages. Atherosclerosis 2006;187:363-371.
31. Sumner MD, et al. Effects of pomegranate juice consumption on myocardial perfusion in patients with coronary heart disease. Am J Cardiol 2005;96:810-814.
32. Seeram NP. Berry fruits: Compositional elements, biochemical activities, and the impact of their intake on human health, performance, and disease. J Agric Food Chem 2008;56:627-629.
In the popular press, there has been a recent focus on "superfoods," or foods that contain high levels of nutrients that some people feel have the best evidence for the prevention or treatment of various medical conditions.Subscribe Now for Access
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