Increased depression risk found through link between high copper and low folate, study flags

14 Aug 2024 --- A synergistic interaction between high copper and low folate levels may increase the risk of depression. This is according to researchers from Guilin Medical College and The University of Hong Kong-Shenzhen Hospital in China, who have established the connection.

Depression is widespread, impacting mental and physical well-being. Previous research observed that high levels of copper in the blood and low levels of folate are linked to depression. 

The current study, published in Frontiers in Nutrition, explored whether serum folate levels, independently or in combination with serum copper levels, were associated with the risk of depression.

The researchers advise that further population-based interventional studies be conducted to confirm whether folic acid supplementation is effective in preventing depression in individuals with high blood copper levels.

Meanwhile, a Korean-based study has found a link between depression and a higher intake of ultra-processed food (UPF) among the female population. Females who consumed the highest measured level of UPF have a 1.51 times higher likelihood of suffering depression than those following a diet high in fruits and vegetables and lower in saturated fat, sugar content and dietary sodium levels, researchers discovered.

Search for trace elements

Folic acid helps protect the blood-brain barrier and reduces copper’s direct damage to brain cells. Copper is transported from the blood circulation into the brain via the blood-brain and blood-cerebrospinal fluid (CSF) barriers. Copper concentration is crucial in oxidative stress processes and influences the catalytic and structural properties of some antioxidant enzymes, which may be one of the leading causes of depression development. 

Data from 4,847 participants in the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2016, aged between 18 and 80 years, were evaluated to determine the exact role of the trace elements. Depression was assessed using the nine-item Patient Health Questionnaire. Finally, logistic regression analyses were employed to determine the main effect of serum copper and folate levels on depression. 

About 8.9% of the participants had PHQ-9 scores above 10, indicating depressive symptoms. After adjusting for all confounding factors, higher serum copper levels and folate deficiency were associated with an increased risk of depression.

High copper levels and low folate levels are associated with the occurrence of depression symptoms and there may be a synergistic effect between them, with this interaction accounting for 19% of depression cases. Further population-based interventional studies are needed to confirm whether folic acid supplementation is effective in preventing depression in individuals with high blood copper levels.The researchers suggest that future studies on the topic be population-based.

There were significant differences between participants with and without depression in terms of age, race, gender, estimated glomerular filtration rate (eGFR), body mass index (BMI), education level, cigarette smoking, self-reported sleep disorder, moderate recreational activities and history of diabetes. Those with depression were more likely to be female, older, non-Spanish, White, have a history of diabetes, have lower eGFR and a higher BMI.

Alarming depression figures

Individuals with a depressive disorder are at increased risk of cardiovascular disease, poor treatment outcomes and increased morbidity and mortality. Worldwide, the number of cases of depression has risen from 172 million in 1990 to 258 million in 2017 (49.9%).   

Research suggests that nutritional compounds can modulate depression-related biomarkers and may play a preventive or therapeutic role in the development and progression of depression.

Copper acts as an electron donor or acceptor for multiple metalloenzymes. Its primary biological functions include maintaining hematopoietic function, affecting energy metabolism and neurobehavioral and immune function. Previous studies suggest that increased levels of blood copper may be associated with depressive disorder, indicating a potential role for copper as a biomarker of depression.

A growing body of research has provided evidence that depression may be linked to folate deficiency. Specifically, studies have shown that folate deficiency is associated with an increased risk of depression, more severe depressive symptoms, longer depressive episodes and an increased risk of relapse of depressive symptoms. Some studies have also found that patients with depression had significant improvement after folic acid supplementation.

Role of nutrients underexplored 

Knowledge about the importance of nutrients in developing depressive symptoms and their intricate interactions is a largely unexplored field of research. Previous cytological studies observed that folate-deficient rat liver cells are more susceptible to copper toxicity, suggesting that there may be a synergistic effect between high blood copper levels and low folate levels.

The researchers recommend including folic acid in US foods and the widespread use of folic acid supplements has eliminated the association between depressive symptoms and folate and copper levels. This suggests that the correlation may be even higher in regions where mandatory folic acid fortification is not practiced or copper levels in the diet are high.

Population-based data do not yet support the hypothesis. To address the knowledge gap, the current study sought to investigate whether serum levels can independently and jointly with serum copper levels affect the risk of depression using data from NHANES.  

 By Inga de Jong