Publishing their study in the American Journal of Clinical Nutrition, the scientists say the findings are relevant given the increasing prevalence of neuro-generative diseases.
Orange juice is rich in flavanones, a sub-class of flavonoids (natural plant phytochemicals) which are easily absorbed by the body.
Adults showed an 8% improvement in cognitive function after drinking orange juice over eight weeks, compared to a control group. However, the mechanisms behind this remain unclear, and researchers recommend further investigation for flavanone-based dietary interventions.
Remembering items on a shopping list
The study took 37 healthy adults with a mean age of 67. Participants consumed 500ml of high-flavanone (305mg) orange juice every day for eight weeks. Another group consumed low-flavanone (37mg) orange-flavoured cordial (of equivalent taste and calorie content).
Global cognitive function (a combined score taken from tests on memory, reaction time and verbal fluency) was ‘significantly better’ after consuming high-flavanone orange juice, say researchers. Participants’ mood and blood pressure remained similar.
“Although evidence for acute, beneficial cognitive effects of flavonoid-rich foods and drinks exists in older populations with mild cognitive impairment, to our knowledge, there have been no such interventions in healthy older adults,” wrote Daniel Lamport, one of the authors of the study.
“The current data showed that cognitive benefits achieved from regular daily flavonoid consumption were not exclusive to adults with mild cognitive impairment or neurodegenerative disease.
“Positive effects for executive function [complex cognitive processes such as solving problems or planning] are of particular relevance because performance on tasks that require these functions are known to deteriorate as a consequence of normal aging, as a result of structural changes that preferentially affect the hippocampus and prefrontal cortex.”
The verbal memory test required participants to learn a list of words, and then recall them both immediately and then after a 30 minute delay. An 8% improvement in this case equated to remembering one more word from a list of 15 shopping items.
The authors say that, although this may be a small improvement over an 8 week period, it could result in substantial improvements over time.
While the scientists are not recommending consuming 500ml of orange juice each day, they hope the findings show that such flavanones could have an important role in a healthy, balanced diet. Previous research from the university has suggested other flavonoid rich foods such as blueberries are good for cognition.
Mechanisms
The study did not investigate the mechanisms for the effects, but suggests possible reasons. Flavonoids may improve blood flow in the brain and protect neurons against oxidative damage, while flavanones may be most likely to target the frontal cortex and hippocampus (areas of the brain essential for executive function and memory).
“Clearly much work is required to examine the potential mechanisms that may underlie the association between flavonoid consumption and cognitive function,” said Lamport. “However, to our knowledge, the current study is the first human intervention trial to show cognitive benefits after flavanone consumption.
“Future research should investigate the potential for flavanone-based dietary interventions to maintain and enhance cognitive function in healthy young adults and attenuate cognitive decline in older adults with neurodegenerative disease.
"Because of the increasing prevalence of ageing-associated neurodegenerative disease in Western populations, it is essential to identify dietary interventions that can be easily understood and adopted by the public.”
Source: American Journal of Clinical Nutrition, doi: 10.3945/ajcn.114.088518.
Title: “Chronic consumption of flavanone-rich orange juice is associated with cognitive benefits: an 8-wk, randomized, double-blind, placebo-controlled trial in healthy older adults”
Authors: R. J. Kean; D.J. Lamport; G.F. Dodd; J.E. Freeman; C.M. Williams; J.A. Ellis; L.T. Butler; and J.P.E. Spencer.