In an evolving health landscape, emerging research continues to highlight concerns that could impact everyday wellbeing. Here’s the key update you should know about:
New research uncovers the brain-boosting power of copper; just the right amount could help older adults stay sharp, especially after a stroke.
Study: Association between dietary copper intake and cognitive function in American older adults: NHANES 2011–2014. Image credit: Danijela Maksimovic/Shutterstock.com
An observational study involving American older adults revealed that higher dietary copper intake is associated with higher cognitive function, especially in individuals with a history of stroke. The study is published in Scientific Reports.
Background
The prevalence of cognitive impairment is steadily increasing worldwide, mainly due to the increasing global aging population. Cognitive decline is a significant sign of all forms of dementia, ranging from mild cognitive impairment to Alzheimer’s disease.
Recent estimates indicate that the prevalence of dementia is expected to reach 152.8 million by 2050. This highlights the need for developing appropriate strategies to reduce the risk of cognitive impairment.
Dietary supplementation with essential micronutrients, including vitamins and minerals, has recently gained considerable attention as a valuable strategy to improve cognition and prevent dementia, especially in the older population. Research has shown that the imbalance of certain micronutrients, such as zinc, selenium, and copper, in the brain can lead to cognitive impairment and the subsequent development of neurodegenerative diseases.
Copper is a vital micronutrient required for the development and functioning of the nervous system. However, an optimal level of copper should be maintained for proper brain functioning, as its deficiency can induce neurological disorders, and its overdose can lead to oxidative stress and neurodegeneration.
In the current study, researchers investigated the non-linear, dose-response association between dietary copper intake and cognitive function in American adults aged 60 years or above.
The study
The study analyzed data of 2420 participants from the 2011 to 2014 National Health and Nutrition Examination Survey (NHANES). The NHANES sample is designed to be nationally representative of the U.S. population.
The information on dietary copper intake was derived from two 24-hour dietary recall questionnaires. Several cognitive function assessments were carried out to explore participants’ memory and executive abilities.
In the NHANES study, participants underwent four cognitive function tests, including the immediate and delayed verbal list learning tests (CERAD-IRT and CERAD-DRT), the Digit Symbol Substitution Test (DSST), and the Animal Fluency Test (AFT). The scores of all these tests were averaged to determine the global cognitive score.
CERAD-IRT and CERAD-DRT were used to assess the capacity for novel linguistic acquisition; DSST was used to measure processing speed and executive function; and AFT was used to measure verbal and executive abilities.
Key findings
The study findings revealed that participants with the highest dietary copper intake have higher cognitive scores than those with the lowest copper intake. A gradual increase in cognitive function was observed with increasing copper intake, indicating a positive but non-linear dose-response relationship.
The study estimated optimal reference thresholds for copper intake, which were 1.63 milligrams per day for the DSST, 1.42 milligrams per day for the AFT, and 1.22 milligrams per day for the global cognitive score.
The positive association between copper intake and cognitive function was observed when the copper intake was lower than these threshold levels. However, when the copper intake exceeded these thresholds, the association followed an inverted L-shaped curve and lost statistical significance. These observations indicate that cognitive function does not continue to increase with increasing copper intake after a certain level.
The subgroup analysis revealed that the positive impact of dietary copper intake on global cognitive function is particularly more pronounced among participants with a history of stroke. Specifically, the increase in the global cognitive Z score in this group was statistically significant (p for interaction = 0.009).
Study significance
The study highlights the importance of dietary copper intake in improving cognitive functions in older adults, especially those with a history of stroke.
Copper is a vital micronutrient that helps regulate various physiological processes, including neurotransmitter synthesis, cellular energy production, and antioxidant defense. It also acts as a cofactor for several enzymes associated with brain function regulation.
Impaired copper homeostasis has been linked to a range of neurodegenerative diseases, including Wilson’s disease and Alzheimer’s disease.
The current study observed a more prominent positive impact of copper intake on the global cognitive score among participants with a history of stroke. Existing evidence also indicates the protective efficacy of copper in reducing stroke risk and attenuating neuronal damage in ischemic stroke.
Copper, as a cofactor for antioxidant enzymes, helps reduce free radical production and prevent oxidative lipid damage in the brain. Copper also helps convert pro-inflammatory macrophages to anti-inflammatory macrophages in the brain, leading to the prevention of neuroinflammation. All these processes highlight the neuroprotective efficacy of copper, which may also ensure cognitive benefits.
Copper-mediated cognitive improvement can also be explained through its effect on neurotransmitter synthesis and release. Existing evidence indicates that copper is crucial in synthesizing acetylcholine, a neurotransmitter involved in learning and memory.
Overall, the study findings indicate that an optimal level of copper intake, with an inflection point of approximately 1.22 milligrams per day, may improve cognitive function in older adults, especially those with a history of stroke. Further randomized controlled trials are necessary to confirm these findings.
However, causal relationships cannot be established due to the study’s cross-sectional design. Residual confounding from unmeasured dietary or lifestyle factors may also influence the results.