Zinc’s important role in the brain and nervous system
We have relatively large quantities of zinc in our central nervous system where it plays a vital role in various physiological and pathological processes. Zinc is also important for brain development, various gene activities, the formation of new neurons, and the immune defense. What is more, zinc is a vital antioxidant that protects the brain against calcification and cell damage caused by oxidative stress. Zinc deficiency is a global problem and may be involved in a number of different neurological diseases – including stroke, cognitive impairment, Alzheimer’s disease, and depression, according to a new review article that is published in Biomolecules.
Zinc is involved in hundreds of different enzyme processes, countless transport proteins (ZIPs), and over 2,800 transcriptional factors that make sure that around 10 percent of the cells’ gene activities are activated at the exact right time. This is why zinc is of vital importance to a host of different physiological processes that include the nervous system, the immune system, the hormone system, and apoptosis (programmed self-destruction of cells). Zinc also supports the very important antioxidant enzyme called SOD (superoxide dismutase) that protects our cells and tissues against free radical damage. Zinc also helps the body in its utilization of vitamin D and vitamin A.
Zinc is one of the must abundant trace elements in the central nervous system where it has many essential roles – from supporting the development of the fetus’ brain to handling various neurological functions throughout life. The brain’s zinc homeostasis, which is a measure of the local zinc balance, is controlled through a complex interplay between different components, including the blood-brain barrier, the activity of the zinc-binding proteins, and the activity of different transport proteins (ZIPs in particular) that carry zinc into our cells.
In the brain, zinc occurs in different forms, for example as zinc ions that are important for regulating neurons, synaptic plasticity, mental balance, learning, and memory.
In their review article, the authors looked at zinc homeostasis and its role in connection with brain health, stroke, brain traumas, and common neurological diseases such as Alzheimer’s disease and depression.
Zinc’s role in the formation of neurons
The formation of new cells and neurons (neurogenesis) plays a vital role in fetal development, which is why zinc is highly important for brain development. Being zinc-deficient during pregnancy and breastfeeding may have a negative impact on the child’s growth and lead to impaired learning skills and memory. It is therefore very important for pregnant and breastfeeding women to get plenty of zinc. In some cases, zinc supplementation can help preterm babies to improved growth and development. Our ability to form new neurons is important throughout life because our brain is more plastic than previously assumed.
Zinc’s role in oxidative stress and chronic disease
Oxidative stress is an imbalance between harmful free radicals and protective antioxidants. We humans generate free radicals as a natural byproduct of different metabolic processes, and it is vital that these free radicals are effectively controlled in order to prevent them from causing cellular damage. It is also potentially harmful if free radicals attack our essential cholesterol and lead to lipid peroxidation, which causes the cholesterol to attach to the blood vessel wall where it triggers inflammation.
Many chronic diseases that are seen in old age such as atherosclerosis, cancer, and dementia are associated with oxidative stress. In this connection, zinc’s important role in supporting superoxide dismutase (SOD) is crucial because of this antioxidant’s ability to protect the cell membranes. Moreover, zinc supports another important antioxidant called glutathione. This is why being zinc-deficient increases your risk of oxidative stress and various diseases later in life.
- Zinc deficiency is a global problem and a contributing factor in many chronic diseases.
Zinc’s role in the immune system of the central nervous system
Zinc-deficient patients have an increased risk of different infections, which is because zinc is of great importance to the innate as well as the adaptive immune systems. Zinc’s role in the immune defense is also linked to zinc transport proteins (ZIPs). Overall, zinc helps regulate inflammatory processes and even a minor zinc deficiency can increase the release of pro-inflammatory cytokines such as TNF-α, IL-1, and IL-6. Most chronic diseases are characterized by chronic low-grade inflammation that is linked to oxidative stress.
In the central nervous system, we have microglia – a type of cells that are part of the innate immune defense. If the brain is exposed to infections or potentially harmful molecules, the microglia produce free radicals and pro-inflammatory cytokines. Studies suggest that zinc can prevent damage to the neurons by controlling the activity of the microglia.
Zinc’s role in stroke
Acute ischemic stroke is the most common type of stroke. Next to heart attacks, they are the most common cause of death worldwide. Acute ischemic stroke occurs when the blood supply to the brain is blocked by thrombotic or embolic occlusion of a cerebral artery. Other processes have also been seen such as neuroinflammation, microglia activation, and overactivation of neurotransmitters such as glutamate.
In connection with ischemic stroke, neurons may release too much zinc, thereby disrupting the brain’s zinc balance. This can cause free radical damage to cells. A zinc imbalance can also result in too little zinc being available for the undertaking of antioxidant actions. Scientists have observed that the zinc concentration in stroke patients is notably lower than the zinc concentration in healthy controls. Studies have also shown that zinc deficiency is linked to more serious cases of brain hemorrhage.
- Zinc’s role in the brain and the central nervous system is highly complex
- All functions are related to the zinc homeostasis
Zinc’s role in Alzheimer’s disease
Alzheimer’s disease is a neurodegenerative disease that affects around 37 million people worldwide. It is characterized by accumulated proteins (amyloid plaque and tau) in the brain that cause local inflammation and a degeneration of cells in the hippocampus, the amygdala, and the neocortex. It takes years for the disease to develop and it results in memory loss, impaired sense of direction and loss of other cognitive skills. Death normally occurs after some years. It has been found that people with Alzheimer’s disease have a disrupted zinc balance in the brain, and zinc tends to accumulate in the late stages of the disease. Also, abnormal changes have been observed in different zinc transporters. It is even possible that zinc is underrepresented as an antioxidant. Imbalances in the zinc homeostasis may possibly play a critical role in the development of Alzheimer’s disease.
Zinc’s role in brain traumas and less mortality
Brain traumas represent a serious health problem that affect around 70 million people every year. The most common causes are accidents, blows, and other types of mechanical damage to the brain tissue. The initial phase of a brain trauma is characterized by reduced blood supply, while the second phase can lead to brain edema, neuroinflammation, oxidative stress, mitochondrial dysfunction, tissue loss, and other harmful chain reactions. Brain traumas can cause a host of mental and motor symptoms and may be life-threatening in worse case.
During brain traumas, zinc plays a vital role in different metabolic processes and as an antioxidant. Scientists have looked at zinc supplements and their potential role in brain traumas. In their review article, the authors refer to a clinical study of 68 people with brain traumas. The participants were divided into two groups, where one group was given 12 mg of zinc daily, while the other group received 2.5 mg of zinc. One month after the trauma, the participants in the group that got the high zinc dose fared better than the low-dose group. Their mortality rate had been reduced by more than 50% (26% versus 12%). Similarly, animal studies have shown that zinc supplementation can improve recovery from brain trauma – including things like mood, learning skills, and memory
Zinc’s role in depression
Depression is a widespread chronic ailment that affects more and more people. It causes symptoms like fatigue, despair, sleep disturbances, and appetite problems. Most people fail to function well socially, and untreated depression is one of the leading causes of suicide.
Studies show that most people suffering from depression have low serum levels of zinc. This may cause changes in the function of the hippocampus and imbalances in the hypothalamic–pituitary–adrenal axis. Depression is also typically associated with chronic brain inflammation.
Thirty years ago, the first hypotheses about a link between zinc and depression surfaced. Animal studies showed that zinc deficiency caused depression-like conditions. On the other hand, zinc supplements could eliminate the symptoms.
Studies of humans have found an inverse relation between zinc levels in serum and the severity of depression. It also appears that women who get too little dietary zinc are more likely than men to have a depression.
Zinc sources and causes of deficiencies
- We get zinc from oysters, liver, meat, dairy products, nuts, seeds, kernels, and beans
- Zinc from animal sources has the best absorption in the body
- Zinc deficiencies can be a result of unhealthy eating habits, ageing, large intake of calcium and/or iron, the use of diuretics, antacids, and ACE inhibitors for treating hypertension and cardiac insufficiency.
References:
Che Li et al. The Important Role of Zinc in Neurological Diseases. Biomolecules. 2023
Ashton Amos, Mohammed S. Razzaque. Zinc and its role in vitamin D function. Current Research in Physiology. 2022
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