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Developing a polyphenol rich seabuckthorn drink to improve cognitive function

Authors:

Abstract

Oxidative damage to the brain results in the decline of many aspects of cognitive function 1. Dietary antioxidants, including polyphenols, have been shown to reduce cognitive decline and improve cognitive function in animals, older individuals, Alzheimer’s patients, and younger populations 2, 3. Seabuckthorn (SB) is a deciduous shrub native to much of the world including the UK. Its berries are high in total phenolics, ranging from 144 to 244 mg/100g 4, and are a rich source of vitamins C, E, and many other nutrients. There have been very few comprehensive studies on the effects of SB polyphenols, including their impact on working memory, which is considered to be a good indicator of cognitive function. Six fruit juice recipes containing SB, with varying health claims including joint health and anti-aging, were consumed as part of a focus group tasting session (n = 40). The rest of this study, carried out with recipes based on the most palatable of these, aimed to determine if short term supplementation with SB could improve working memory test results, whether SB polyphenols were bioavailable, and if routine consumption of dietary antioxidants affected working memory. Two placebo controlled trials were conducted. In the first, participants (n = 12) consumed 150ml of a SB juice for 7 days. In the second trial participants (n = 10) consumed 100ml of a SB juice for 12 days. Acute effects on working memory were assessed by Digit Span (DS), Corsi Block, and Word Span tests. Fruit juices and 24 hour urine collections were analysed by FRAP (antioxidant), and total phenolic assays. Vitamin intake was assessed by food frequency questionnaire. SB has an unpleasant odour and taste, but in appropriate fruit juice cocktails it is possible to counter this whilst still maintaining high phenolic and antioxidant content. Mean urinary phenolics increased after the intervention (P = 0.004) compared to placebo. The second trial had no effect on cognitive function, but in the first, the SB group experienced a significant increase in DS scores after the intervention (p = 0.017), while the placebo group did not. Dietary vitamin C, E and β-carotene showed a strong positive correlation with DS score. We concluded that the polyphenols in the SB recipes are bioavailable, and could benefit on cognitive function, although further study is needed. Also, routine consumption of dietary antioxidant vitamins may benefit cognitive function. 1. Reiter, R.J. 1995. Oxidative processes and antioxidative defence mechanisms in the ageing brain. FASEB Journal, 9 (7), pp.526-533. 2. File, S.E., Jarrett, N., Fluck, E., Duffy, R., Casey, K. and Wiseman, H. 2001. Eating soya improves human memory. Psychopharmacology, 157, pp.430-436. 3. Kennedy, D.O., Scholey, A.B. and Wesnes, K.A. 2000. The dose-dependent cognitive effects of acute administration of Ginkgo biloba to healthy young volunteers. Psychopharmacology, 151, pp.416-423. 4. Gao, X., Ohlander, M., Jeppsson, N., Björk, L. and Trajkovski, V. 2000. Changes in antioxidant effects and their relationship to phytonutrients in fruits of sea buckthorn (Hippophae rhamnoides L.) during maturation. Journal of Agricultural & Food Chemistry, 48 (5), pp.1485-1490.
Developing a Polyphenol Rich
Seabuckthorn Drink to Improve
Cognitive Function
J Wallace, C Tsang, J McGeachie and M Warnock
School of Health Sciences, Queen Margaret University, Edinburgh
Introduction
Many aspects of cognitive performance and memory decline
throughout adulthood, due in part, to oxidative damage in the
brain 1. Dietary antioxidants, including polyphenols, have been
shown to reduce cognitive decline and improve acute cognitive
function in animals, older individuals, Alzheimer’s patients, and
younger populations 2, 3.
Sea buckthorn (SB) is a deciduous shrub native to much of the
world including the UK. Its berries are high in total phenolics,
vitamins C and E, and many other nutrients 4, 5. There have been
very few comprehensive studies on the effects of SB
polyphenols.
Working Memory:
The set of mental processes that make a limited amount of
information temporarily accessible for the completion of cognitive
tasks. It is closely linked with how we learn, understand, and
reason, and a good indicator of cognitive function 6.
Aims:
1. To develop an acceptable SB fruit juice supplement and assess
its polyphenol bioavailability.
2. Determine its impact on working memory test results in a
healthy non-elderly population.
3. Investigate whether routine consumption of an antioxidant
rich diet could improve working memory.
Methods
Six fruit juice recipes containing SB were consumed in a focus
group tasting session (n = 40) and assessed for palatability.
Based on the results of this, two placebo controlled trials were
conducted.
Working memory tests: number recall was assessed by Digit
Span test, spatial memory with the Corsi Block test 6, and word
processing and recall with the Word Span test 7.
Study 2
Placebo controlled supplementation with 150ml
fruit juice for 7 days
Intervention juice was 20% sea buckthorn, 80%
red grape juice, placebo was water.
Dietary vitamin intake assessed at baseline by
food frequency questionnaire.
Study 1
Participant blind placebo controlled cross-over trial in
polyphenol restricted individuals (n = 10) consuming 100 ml/day
for 12 days of an intervention or control juice, split by a 3 day
washout.
Intervention juice was 37% grapefruit, 40% pineapple, 20% SB
and 3% sucrose. For the placebo, water replaced SB.
The juices and 24 hour urine collections (for bioavailability)
were assessed by FRAP (antioxidant 8, and total phenolics 9
assays.
Bioavailability of SB polyphenols
The test juice was higher in polyphenol content (figure 1) and
antioxidant capacity than the placebo
Mean urinary phenolics increased significantly after the
intervention treatment (P = 0.004) but not the placebo (figure 2).
0
500
1000
1500
Control recipe
SB recipe
GAE (mg/l)
Figure 1: Total polyphenol content of juice recipes
0
50
100
150
200
250
300
350
400
Baseline
Control
Phenolic content (mg/l GAE)
Figure 2: Mean total phenolics in 24h urine samples
SB and cognitive
function
In study 2 the juice intervention
group experienced a
significant increase in Digit
Span scores after the
intervention (p = 0.017), while
the placebo group did not
(figure 6). There were no
significant effects in study 1.
0
2
4
6
8
10
12
14
Baseline
After 7 days
Mean Digit Span Score
Control
Figure 6: Mean Digit Span scores, study 2
Dietary antioxidants
and working memory
Dietary vitamin C, E and β-
carotene showed a strong
positive correlation with Digit
Span score (figures 2, 3 & 4).
R = 0.828
0
2
4
6
8
10
12
14
0100 200 300 400 500 600 700 800 900
Digit Span score
Average vitamin C intake (mg/day)
Figure 3: Digit Span score and vitamin C intake
R = 0.684
0
2
4
6
8
10
12
14
0 5 10 15 20 25
Digit Span score
Average vitamin E intake (mg / day)
Figure 4: Digit Span score and vitamin E intake
R = 0.565
0
2
4
6
8
10
12
14
05000 10000 15000 20000 25000
Digit Span score
Average β-carotene intake (μg / day)
Figure 5: Digit Span score and β-carotene intake
Conclusions
The polyphenols in SB are bioavailable, and may have some
benefit to cognitive function, although further study is needed in
this area.
Routine consumption of dietary antioxidant vitamins was shown
to correlate with cognitive function.
While the effects of supplementation with SB remain
inconclusive, this study provides evidence to show that a
diet rich in high-antioxidant fruit and vegetables may benefit
cognitive function.
6. Zeb, A., 2004. Chemical and nutritional constituents of sea buckthorn juice. Pakistan Journal of Nutrition, 3 (2), pp.99-106.
7. Baddeley, A. 2003. Working memory: looking back and looking forward. Nature Reviews, 4, pp.829-839.
8. Friedman, N.P. and Miyake, A. 2004. The reading span test and its predictive power for reading comprehension ability. Journal of
Memory and Language, 51, pp.136-158.
9. Benzie, I.F.F., and Strain, J.J. 1996. The ferric reducing ability of plasma (FRAP) as a measure of “Antioxidant power”. The FRAP
assay. Analytical Biochemistry, 239, pp.70-76.
10.Singleton, V.L. and Rossi, J.A. 1965. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic reagents. American
Journal of Enology and Vitology, 16, pp.144-158.
References
1. Reiter, R.J. 1995. Oxidative processes and antioxidative defence mechanisms in the ageing brain. FASEB
Journal, 9 (7), pp.526-533.
2. File, S.E., Jarrett, N., Fluck, E., Duffy, R., Casey, K. and Wiseman, H. 2001. Eating soya improves human memory.
Psychopharmacology, 157, pp.430-436.
3. Kennedy, D.O., Scholey, A.B. and Wesnes, K.A. 2000. The dose-dependent cognitive effects of acute
administration of Ginkgo biloba to healthy young volunteers. Psychopharmacology, 151, pp.416-423.
4. Gao, X., Ohlander, M., Jeppsson, N., Björk, L. and Trajkovski, V. 2000. Changes in antioxidant effects and their
relationship to phytonutrients in fruits of sea buckthorn (Hippophae rhamnoides L.) during maturation. Journal of
Agricultural & Food Chemistry, 48 (5), pp.1485-1490.
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