Subjective memory impairment (SMC) refers to the perception of decline in memory and cognitive function in individuals without a diagnosed cognitive disorder.
SMC is associated with reduced quality of life, increased risk of depression, and negative impacts on daily life. Each year, approximately 2.3% and 6.6% of older adults with SMC are reported to progress to dementia and mild cognitive impairment (MCI), respectively.
Dietary factors, particularly foods rich in antioxidants, have been shown to prevent cognitive decline and memory-related symptoms.
For example, studies have shown that antioxidant-rich grapes and astaxanthin taken alone may have neuroprotective effects.
Australian researchers conducted a randomized, double-blind, placebo-controlled trial to investigate the effects of a multi-nutrient supplement containing astaxanthin, vitamin E, and grape juice extract on memory and cognitive function.
The study was funded by US company NSE Products Inc, which also provided the dietary supplements and placebos provided to participants.
One hundred men and women aged 40 to 75 years with SMC were randomly assigned to either the supplement or a placebo group.
The intervention contained 9 mg astaxanthin, 250 mg grape juice extract, and 12 mg vitamin E (d-alpha tocopherol). The softgel excipients consisted of olive oil, sunflower lecithin, yellow beeswax, fish gelatin, glycerin, and water.
Participants were asked to take two capsules once daily with a meal for 12 weeks.
They found that supplementation was associated with significantly greater improvements in episodic memory (p = 0.037) compared to the placebo group, but not in working memory (p = 0.418) or verbal learning (p = 0.841).
However, based on results from the Everyday Memory Questionnaire (EMQ), a self-reported assessment of cognitive ability, participants in the intervention group showed greater improvement in their memory over time (42 percent) compared with the placebo group (18 percent).
Other self-reported outcome measures of stress, general health, and eye and skin health showed no differences between the two groups.
“Episodic memory is a cognitive process that involves the retention, recall, and encoding of information about experiences and events related to a specific time and place. It is thought to be the memory system most sensitive to age. Deterioration of episodic memory is one of the earliest and most common symptoms of MCI. Severe deficits in this cognitive process are seen in people with Alzheimer’s disease.”
“Given the promising improvements in episodic memory observed in this study, we speculate that the intervention supplement may have a protective effect on this region of the brain. Further research is essential to extend and validate the current findings.” The authors write:
No significant differences were found between the groups on measures of working memory, verbal learning and memory, information processing speed, attentional accuracy, or visuospatial learning, although it is possible that participants with problems in these areas were not specifically recruited into the study.
“The results suggest that the dietary supplement, administered for 12 weeks, had no effect on cognitive and brain regions important for sustained focus, attention, and vigilance. Future trials in people with deficits in attention and working memory will be important in substantiating these null effects.”
Anti-inflammatory and antioxidant properties
To examine the anti-inflammatory and antioxidant effects of the supplements, we measured changes in blood markers of inflammation and oxidative stress, including brain-derived neurotrophic factor (BDNF), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and malondialdehyde (MDA).
The intervention group experienced a statistically significant 46.10% increase in BDNF concentrations from baseline to week 12 (p < 0.001), compared with a 24.41% increase in the placebo group (p < 0.001).
BDNF plays an important role in neuronal survival and growth, which are essential for learning and memory, and synaptic plasticity, and it has anti-inflammatory effects on microglia, cells in the central nervous system that protect the brain from environmental stress.
“This suggests that the neuroprotective effects of this dietary supplement may be due to its ability to increase BDNF, an important neurotrophic factor.”
Regarding MDA levels, the supplement group showed a non-significant decrease of 12.49% (p = 0.294) and the placebo group showed a nearly significant increase of 26.52% (p = 0.072).
In a previous study in patients with recurrent depression, elevated plasma MDA concentrations were associated with worsening cognitive performance.
Further analysis demonstrated that there were significant differences between groups regarding changes in BDNF (p = 0.037) and MDA (p = 0.020), but not regarding changes in TNF-α (p = 0.531) and IL-6 (p = 0.728).
Furthermore, skin carotenoid concentrations were increased in the intervention group compared with the placebo group. Because carotenoids are potent antioxidants, this dietary supplement may have exerted its neuroprotective effects via its antioxidant properties.
“Overall, the supplement was well tolerated, with no serious side effects or significant changes in safety blood markers related to kidney or liver function reported.
“Although the study recruited participants with self-perceived cognitive impairment, validated assessments indicated minimal to no cognitive impairment. Therefore, testing in a larger sample of patients with diagnoses such as MCI would help to better define the efficacy of this dietary supplement and understand its mechanism of action.”
sauce: Nutrients
https://doi.org/10.3390/nu16111770
“Investigating the effects of dietary supplements on cognitive function, stress, eye health, and skin satisfaction in adults with cognitive impairment: a randomized, double-blind, placebo-controlled trial”
Author: Adrian L. Lopresti, others
