Purple Foods Rich in Anthocyanins Can Improve Cognitive Function

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    Anthocyanins are blue, violet, or red pigments found in plants. Food plants rich in anthocyanins include blueberries, cherries, purple grapes and purple sweet potatoes. Anthocyanins belong to the flavonoids family. Evidence suggests that flavonoid-rich foods are capable of inducing improvements in memory and cognition in animals and humans.

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    Blueberries are rich in anthocyanins (member of flavonoids), and blueberries possess antioxidant and anti-inflammatory properties known for cognition benefits. However, there is a lack of clarity concerning whether anthocyanins/flavonoids are the causal agents in inducing such beneficial response.

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    In order to test this question, a rat study was conducted. Supplementation with pure anthocyanins or flavonoids for 6 weeks at levels similar to those found in blueberries resulted in an enhancement of spatial memory in 18-month-old rats. Pure flavonoids and anthocyanins were observed to induce significant improvements in spatial memory similar to the results following blueberry supplementation. These behavioral changes were paralleled by increases in the hippocampal brain-derived neurotrophic factor, suggesting a common mechanism for the enhancement of memory. The rat study data supported the claim that anthocyanins are likely causal agents in mediating the cognitive effects of blueberries (1).

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    A group of healthy adults who were 60-years-old and older drank either 30 mL blueberry concentrate (containing~ 387 mg anthocyanins) or placebo for 12 weeks.  Pre- and post-supplementation, study participants undertook cognitive function tests while functional magnetic resonance images were continuously acquired. Significant increases in brain activity were observed in response to blueberry supplementation compared to the placebo group within Brodmann areas 4/6/10/21/40/44/45, precuneus, anterior cingulate, insula and thalamus. In addition, there were significant improvements of the rate at which blood is delivered to grey matter tissue in the parietal and occipital lobes. Supplementation with an anthocyanin-rich blueberry concentrate improved the rate of blood delivered to the brain, activated brain areas associated with cognitive function, and improved working memory in healthy older adults (2).

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    Since both fish oil and blueberry are known for neurocognitive benefit, a group of scientists conducted a long-term supplementation of daily fish oil or blueberry or both for 24 weeks in adults 60-years-old and older with cognitive problems. Both fish oil (1.6 g EPA and 0.8 g DHA/day) and blueberry (frozen blueberries were made into powders ~ 362.5 mg anthocyanins per day) groups reported fewer negative cognitive problems. The blueberry group showed improved memory discrimination (improved resistance to interference of extraneous material in memory). Cognitive benefit in the blueberry group was associated with presence of urinary anthocyanins reflecting recent blueberry intake. The effect for improved function in everyday activities was apparent in both of the individual fish oil or blueberry treatment groups, but fish oil plus blueberry combination treatment did not have cognitive enhancement as expected (3).

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    A group of adults who were 70-years-old and older with mild-to-moderate dementia (n = 49) ingested 200 ml/day of either an anthocyanin-rich cherry juice or a control juice with little anthocyanin content (with ~ 138 mg more anthocyanins/day) for 12 weeks. The group of people who received the cherry juice treatment significantly improved in cognitive performance with better verbal fluency, and better short-term memory and long-term memory (recalling more animals and words over time) compared to those of control group. The cherry juice group also had benefits in blood pressure after 12 weeks with a significant reduction in systolic blood pressure from 138.2 ±16.4 to 130.5 ± 12.2 mmHg (mean ±standard deviation) and a trend for diastolic blood pressure reduction (4).

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    Increased stress can impair cognitive function. Effects of daily consumption of Concord grape (purple grape) juice on cognition was studied in individuals with somewhat stressful and demanding lifestyles. Healthy mothers at ages 40-50 years old who had at least one preteen child and were employed for more than 30 hours per week drank 12 ounces (355 ml) of either Concord grape juice (containing ~ 167 mg anthocyanins) or a matched placebo juice daily for 12 weeks.  Compared to those of the control group, the women who had the Concord grape juice significantly improved immediate spatial memory, and better cognitive test results in complex everyday tasks such as driving performance. Specifically, Concord grape juice drinking was associated with a reduced phase shift in car following, which was comparable to a quicker reaction time to unfolding traffic events. This meant increased steering accuracy in combination with a faster response time to changes in lead vehicle behavior during car following. The observed effects would account for a quicker stop with farther 11 meters away than those of the control group at the speeds driven at 40–60 mph or 64–97 km/h, which is an important safety benefit. Thus, the cognitive effects of long-term grape juice consumption can translate into meaningful outcomes on everyday tasks (5).

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    The effects of 230 ml purple grape juice (containing ~32 mg anthocyanins) or a control juice were assessed in 20 healthy young adults. This study demonstrated that purple grape juice could immediately enhance cognition and mood. Compared to the sugar-matched, control drink, purple grape juice enhanced overall speed on attention tasks and significantly increased the rating for calmness (6).

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    Purple sweet potato color, a naturally occurring anthocyanin, has a powerful antioxidant activity. A mice study explored whether purple sweet potato color (high with anthocyanins) has the neuroprotective effect on the aging mouse brain induced by D-galactose. The mice administrated with purple sweet potato color showed significantly improved behavior performance in the open field and passive avoidance test. D-galactose could remarkably lead to the impairment of learning and memory in mice. There appeared a significant effect of purple sweet potato color on the improvement of brain functions during aging. It significantly inhibited the behavioral retrogression induced by D-galactose. It could also reverse the impairment of learning and memory in D-galactose-treated mice. Study data suggested that purple sweet potato color attenuated cognitive impairment partly via enhancing the antioxidant and anti-inflammatory capacity (7).

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    Inclusion of an anthocyanin-rich food or beverage may be a practical and feasible way to improve total anthocyanin consumption for all ages. With more intakes of purple-color foods such as blueberries, cherries, purple grapes and purple sweet potatoes, there is potential to improve cognitive outcomes.

 

References:

1. Rendeiro C1, Vauzour D, Rattray M, Waffo-Téguo P, Mérillon JM, Butler LT, Williams CM, Spencer JP. Dietary levels of pure flavonoids improve spatial memory performance and increase hippocampal brain-derived neurotrophic factor. PLoS One. 2013 May 28;8(5):e63535.

2. Bowtell JL, Aboo-Bakkar Z, Conway ME, Adlam AR, Fulford J. Enhanced task-related brain activation and resting perfusion in healthy older adults after chronic blueberry supplementation. Appl Physiol Nutr Metab. 2017 Jul;42(7):773-779.

3. McNamara RK, Kalt W, Shidler MD, McDonald J, Summer SS, Stein AL, Stover AN, Krikorian R.Cognitive response to fish oil, blueberry, and combined supplementation in older adults with subjective cognitive impairment. Neurobiol Aging. 2018 Apr;64:147-156.

4. Kent K, Charlton K, Roodenrys S, Batterham M, Potter J, Traynor V, Gilbert H, Morgan O, Richards R. Consumption of anthocyanin-rich cherry juice for 12 weeks improves memory and cognition in older adults with mild-to-moderate dementia. Eur J Nutr. 2017 Feb;56(1):333-341.

5. Lamport DJ, Lawton CL, Merat N, Jamson H, Myrissa K, Hofman D, Chadwick HK, Quadt F, Wightman JD, Dye L. Concord grape juice, cognitive function, and driving performance: a 12-wk, placebo-controlled, randomized crossover trial in mothers of preteen children. Am J Clin Nutr. 2016 Mar;103(3):775-83.

6. Haskell-Ramsay CF, Stuart RC, Okello EJ, Watson AW. Cognitive and mood improvements following acute supplementation with purple grape juice in healthy young adults. Eur J Nutr. 2017 Dec;56(8):2621-2631. doi: 10.1007/s00394-017-1454-7.

7. Shan Q1, Lu J, Zheng Y, Li J, Zhou Z, Hu B, Zhang Z, Fan S, Mao Z, Wang YJ, Ma D. Purple sweet potato color ameliorates cognition deficits and attenuates oxidative damage and inflammation in aging mouse brain induced by d-galactose. J Biomed Biotechnol. 2009;2009:564737.