The effects of berry juice on cognitive decline in older adults : a thesis presented in partial fulfilment of the requirements of Master of Arts in Psychology at Massey University, Palmerston North, New Zealand
This study examined the effects of blackcurrant and boysenberry juices on cognitive processes in older adults. Current research suggests that fruits such as these may be able to reverse some of the effects of ageing on cognition. The free radical theory of ageing proposes that individuals age because oxidative damage accumulates in cells and interferes with cell functions. The hardest working tissues such as the brain accumulate the most oxidative damage through respiration. Antioxidants can protect against free radical formation and damage. Anthocyanins can contribute to half of the antioxidant capacity of deeply coloured berry fruit. An increase in dietary antioxidants such as anthocyanins may help to alleviate free radical damage within the brain. Research has shown that oxidative damage within the brain can impair cognitive functioning. Working memory shows age-related decline, along with visuospatial abilities, word retrieval and sustained attention. Some of this decline is thought to be related to oxidative damage of neurotransmitters such as acetylcholine and areas of the brain such as the hippocampus. Past research with humans has shown that some antioxidants can affect cognitive functioning in an older population. Animal studies have also established that diets enriched with anthocyanins can improve memory, motor control and neurotransmitter functioning. The present study involved giving berry juice drinks to 52 older adults that had been assessed as having a mild impairment of cognitive function. The participants were divided into three groups and drank 200mL a day of either blackcurrant juice, boysenberry juice or a placebo for twelve weeks. The participants were assessed at three different times over the course of the experiment using the RBANS. The RBANS is sensitive to small changes in its tests of memory, visuospatial ability, language and attention. The results of this study did not support previous research on antioxidants and cognitive functioning. There were no significant interactions between berry juices and any of the cognitive domains assessed by the RBANS over the course of the experiment. Some of the limitations of the study may be responsible for a lack of effect. The experiment was short with a low dose of antioxidants, and there was little control over the participants altering their own diet after being informed of the reasoning behind the study.