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HerbClip: Açaí Anthocyanin Content and its Absorption and Plasma Antioxidant Effects in Humans Differ with Fruit Pulp Ingestion Compared to that Juice
Re: Açaí Anthocyanin Content and its Absorption and Plasma Antioxidant Effects in Humans Differ with Fruit Pulp Ingestion Compared to that Juice
Mertens-Talcott SU, Rios J, Jilma-Stohlawetz P, 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. Sep 10, 2008;56(17): 7796-7802.
A variety of açaí (Euterpe oleracea) fruit products have
become very popular in recent years, but more research is needed to determine
their effects on human health.1 Açaí fruit is harvested by hand
from wild açaí palms in the Amazon River Basin. They contain large amounts of
polyphenols, natural products that are potent antioxidants. Polyphenols may
also modulate cellular signaling. Pre-clinical research on whole açaí fruit has
demonstrated antioxidant and anti-inflammatory effects. In this small clinical
study, the authors examine the absorption and kinetics of anthocyanins from
açaí pulp and its clarified juice and the effects on plasma antioxidant
activity.
Healthy subjects (aged
21-31) were recruited at the University
of Florida in Gainesville, Florida.
Out of 11 subjects who completed the açaí pulp, açaí juice, and applesauce
phases of the study, 7 also completed the non-antioxidant beverage control
phase. No adverse side effects were observed during the study. Pasteurized,
frozen açaí pulp from Brazil
(Bossa Nova Beverage Group, Los
Angeles, California)
was used in the study. Clarified açaí juice was produced from the pulp using
centrifugation and filtration. The non-antioxidant control beverage was made
from deionized water. Applesauce (manufacturer not stated) was used as an
anthocyanin-negative control food; no other information regarding the
applesauce is provided. Sucrose was added to the acai pulp, juice, and control
beverage to adjust the soluble solids content to match the applesauce. Following
a 72-hour wash-out phase in which the subjects followed a diet low in
antioxidants and polyphenols, they fasted for 8 hours before the study day. On
study days, the subjects received 7 mL/kg of the study treatments.
Phytochemical analysis of
the açaí fruit pulp revealed that it contained high concentrations of
anthocyanins. The methanol extract contained 972±27 mg/kg total anthocyanidins
as cyandin-3-glucoside, while the water-soluble extract from the clarified
juice contained only 531±0.2 mg/L. This difference indicates that a large
portion of the anthocyanins in the pulp are bound to its insoluble fiber. The
subjects' plasma anthocyanin concentrations were significantly higher 0.5-4
hours following ingestion of the açaí pulp compared to the açaí clarified juice
(P≤0.05). The authors write that this indicates "that anthocyanins bound
or trapped within the water-insoluble cellular matrix of the pulp were
liberated in the intestinal tract and available for absorption." They also
write that this was demonstrated by the slightly higher time of maximum
concentration (tmax) for açaí pulp (2.2 hours) compared to the açaí
juice (2.0 hours). The maximum concentration (Cmax) was 2321 ng/L
for açaí pulp and 1138 ng/L for açaí juice. The açaí fruit pulp also had higher
values for half-life (pulp: 6.56 hours, juice: 3.00 hours) and area under the
curve (AUC) (pulp: 8568 ng/L, juice: 3314 ng/L) compared to açaí juice.
Statistical analysis (nonlinear mixed effect modeling) showed a low oral
bioavailability for açaí anthocyanidins, with the relative bioavailability
actually decreasing as the dose increased.
All treatments caused a
statistically significant increase in plasma antioxidant capacity 0.50-4.0
hours following consumption compared to the non-antioxidant control beverage
(P<0.01 for all). Açaí pulp and applesauce caused higher plasma antioxidant
levels than açaí juice (P<0.05). There was not a significant overall
difference between the treatments' effects on the antioxidant capacity of the
subjects' urine. Urine antioxidant capacity was significantly higher for the
açaí juice and pulp and the applesauce than for the nonantioxidant control
beverage 9-12 hours following treatment (P<0.05). The authors write that
higher doses may be necessary to obtain more significant results on urine
antioxidant capacity. None of the treatments produced significant effects on
the subjects' plasma uric acid levels, which indicates that fructose was
probably not a major contributor to differences in antioxidant effects. The
generation of reactive oxygen species (ROS) in the subjects' peripheral blood
mononuclear cells was also not significantly affected by any of the
treatments.
In this study, anthocyanins
from açaí fruit juice and pulp were shown to be bioavailable in healthy humans
following oral consumption, and consumption of açaí products was shown to
increase plasma antioxidant capacity. The authors write that further studies
are needed on the metabolism of açaí polyphenols and to confirm açaí's
antioxidant effects and potential health benefits. The study does contain
weaknesses including the fact that characterization data of the açaí pulp are
not included in the article beyond identification of its commercial source.
Without more precise information, the study cannot be accurately duplicated. It
is unclear how the researchers determined that subjects did indeed follow a
diet low in antioxidants and polyphenols during the wash-out phase, though the
8-hour fast prior to treatment should have eliminated most confounding factors.
The authors have unfortunately limited
their focus to açaí's
polyphenols which is another weakness of the study. This fruit is unique among
fruits because of its unusually high mono- (MUFA) and poly-unsaturated (PUFA)
fatty acid concentration, higher than olives or avocadoes. This attribute in
itself may be contributing to its various observed properties in vitroand in vivo. Unfortunately,
clarification and filtering of açaí
pulp is a common practice and, as noted by the authors, reduces the
concentrations of the lipid MUFAs and PUFAs and other constituents found in the
fruit juice, further reducing the juice's potential health.
These weaknesses do not negate the reported
antioxidant capacity of açaí
pulp described by the authors. The real value that comes from the study is the
clear-cut suggestion that clarifying and filtering out açaí pulp from an açaí
juice beverage may significantly reduce its health benefits. The data argue
that giving the whole fruit, in this case açaí fruit, is demonstrably better than its clear filtered juice.
—Marissa Oppel, MS
References
1.Glenn L. Popularity vs. clinical studies - açaí
berries have the popular vote. HerbClip
News. April 13, 2007.