12 January - 20 June 2016

Consuming avocado may improve eye health and memory

A study published in Nutrients by scientists from Tufts University has investigated the effect of avocado consumption on cognition. Lutein, a dietary carotenoid found in avocados, can cross the blood-brain barrier and accumulate in the macular region of the eye retina. Retinal lutein has been found to be associated with lutein brain concentrations, with previous studies suggesting that lutein in the brain of older adults are positively associated with “a variety of pre-mortem cognitive measures.”

A study published in Nutrients by scientists from Tufts University has investigated the effect of avocado consumption on cognition. Lutein, a dietary carotenoid found in avocados, can cross the blood-brain barrier and accumulate in the macular region of the eye retina. Retinal lutein has been found to be associated with lutein brain concentrations, with previous studies suggesting that lutein in the brain of older adults are positively associated with "a variety of pre-mortem cognitive measures."

The six month, randomised, controlled trial by Johnson et al. randomly assigned 20 healthy men and women, aged over 50 years, into two groups.  One group consumed one avocado (135 g) daily containing around 0.5mg of lutein and 13 g/day monounsaturated fat and the other a potato or cup of chickpeas containing no lutein and <1 g/day monounsaturated fat.   The total amount of lutein was calculated to be 90 mg over the course of the study.  At baseline, three and 6 months, serum lutein, macular pigment density (MPD) and cognition were measured.  Cognitive tests included memory, processing speed and attention. 

Johnson et al. report that at baseline there was no significant differences between the two groups in terms of age, body mass index, education, lutein, monounsaturated fat intake, amongst others.  Although the study does note that at baseline the avocado group had better short term visual memory.  During intervention, there was no significant changes in dietary habits or body weight for either group.  Compared to baseline, at 3 and 6 months the scientists report that there was an increase in serum lutein concentration, "with increase that were >25% for both time points."  After intervention, there was a 15% increase in serum lutein in the control group with serum zeaxanthin "significantly increased by >20% at both time points".  For both groups, oxidative stress and inflammation remained unchanged throughout the study compared to baseline. The participants in the avocado group experienced significant increases in MPD after intervention with increases of more than 25% at both three and six months whilst the control group, increased by 17% at three months, however this increase was not sustained at 6 months.

Whilst both groups improved in memory and spatial memory, which the researchers reported could be due to familiarisation, only the avocado group improved in sustained attention. The team report that “in the avocado group, the change in MPD was significantly related to changes in Spatial Working memory”.  However, “there were no relationships between the change in MPD and the change in cognition in the control group.”

In discussion, the authors suggest that the cognitive function improvement in the avocado group "could be related to the increase in MPD, a biomarker of lutein contained in brain tissue." They suggest that lutein may act as an antioxidant or anti-inflammatory agent.  They also propose that lutein may embed in neural tissues modulating the functional, physiochemical and structural properties of synapatic membranes.

RSSL’s Functional Ingredients Laboratory can analyse for lutein and zeaxanthin in foodstuffs.  .  For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com


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