Selenium supplements have a positive effect on brain health and Alzheimer’s disease

The brain is particularly vulnerable towards oxidative stress and local inflammation that can set the stage for Alzheimer’s disease and other neurological conditions. However, it turns out that certain selenium-containing antioxidants are able to protect the brain neurons against damage. Also, selenium supplements can improve cognitive performance in patients suffering from mild cognitive impairment and Alzheimer’s disease, according to a meta-analysis that is published in Nutrients.

For their meta-analysis, the scientists gathered data from four electronic databases, ending up with six eligible clinical studies published before December 2020. Most of the studies were from Europe and the United States. Sixty percent of the study participants suffered from Alzheimer’s disease, while 40 percent had mild cognitive impairment. As part of these studies, the participants were given supplements of selenium for 12-24 weeks.
The meta-analysis showed that selenium supplementation increased the activity of a selenium-containing antioxidant called glutathione peroxidase (GPX). Also, selenium improved the mental performance of patients with mild cognitive impairment and Alzheimer’s disease when they were tested. The scientists assume that selenium supplements are a viable alternative for patients with these conditions. It also appears that sufficient intake of selenium helps prevent mild cognitive impairment and Alzheimer’s disease.

• Free radicals are natural byproducts of the cellular energy turnover
• The free radical burden is increased by ageing, poisoning, smoking, overweight, inflammation, and chronic disease
• Oxidative stress is an imbalance between harmful free radicals and protective antioxidants
• In oxidative stress, the free radicals outnumber the antioxidants and attack and destroy neurons and other cell types

Why does the brain need selenium?

Selenium is an essential trace element that supports around 25 different selenium-containing proteins. Several of these so-called selenoproteins have antioxidant functions like the unique GPX antioxidant that protects the brain cells against free radical damage and oxidative stress.
The brain accounts for close to 20 percent of the body’s total oxygen consumption, and because brain tissue harbors large quantities of polyunsaturated fatty acids it is a target for oxidative stress. Free radicals are particularly harmful when they attack polyunsaturated fatty acids in the cell membranes and initiate chain reactions that spread to other cells. This phenomenon is known as lipid peroxidation. If the free radical attacks are too massive, they may damage the cellular DNA and several enzyme functions, thereby causing the cells to malfunction or perish. The selenium-containing antioxidants also protect against chronic brain inflammation. This inflammation is not something one can feel but it is involved in a host of different neurological disorders, nonetheless.

The link between mild cognitive impairment, Alzheimer’s disease, and selenium deficiency

More and more older people across the globe suffer from mild cognitive impairment, which can be an early stage of Alzheimer’s disease, the leading cause of dementia. Researchers have found that neurodegenerative diseases like Alzheimer’s are characterized by oxidative stress. Also, it has been observed that patients with Alzheimer’s disease accumulate a type of harmful proteins in the brain, something known as beta-amyloid plaques. This triggers inflammation, cell death, and various symptoms such as memory loss, poor sense of direction, and loss of other skills. It has also been observed that Alzheimer’s patients have significantly lower levels of selenium in their blood serum and in the red blood cells compared with healthy peers. The scientists behind the new meta-analysis say that this is the first time anyone has demonstrated that selenium supplements have a positive effect on patients with mild cognitive impairment and Alzheimer’s disease.
It appears that selenium is able to prevent beta-amyloid plaque formation and the activity of iron-containing free radicals in the brain. According to the researchers, the positive effects are a result of increased activity of GPX antioxidants that protect brain neurons.

Selenium improves cognitive skills

Different tests such as MMSE (Mini-Mental State Examination) are used to assess the progression of Alzheimer’s disease with regard to language, memory, sense of direction, calculation, and writing and drawing skills. The higher the score, the better the cognitive skills. According to the new meta-analysis, selenium supplementation significantly improved the patients’ cognitive skills in the MMSE test. Another study published in Cell Metabolism shows that selenium has a key role in the formation of new neurons.

How does one raise selenium levels in the blood?

The official recommendation for selenium in Europe and the United States is around 55 micrograms daily. Still, studies suggest that it takes around 100 micrograms per day in order to properly saturate selenoprotein P, which is used as a gauge for the body’s selenium status. According to the present meta-analysis, it is also important to optimize levels of GPX in blood serum and in the blood red cells. In any case, blood levels of selenium should ideally lie in the range of 70-130 micrograms.
Selenium intake levels vary a lot depending on geography and soil conditions. Data from Europe, China, Asia, the Middle East, and Africa suggest that the selenium intake is too low. It is also important not to overdose on selenium, however. The safe upper intake level according to WHO is 400 micrograms per day.

Referencer:

Meire Ellen Pereira et al. Effects of Selenium Supplementation in Patients with Mild Cognitive Impairment or Alzheimer’s Disease: A Systematic Review and Meta-Analysis. Nutrients 2022

Odette Leiter et al. Selenium mediates exercise-induced adult neurogenesis and reverses learning deficits induced by hippocampal injury and aging. Cell Metabolism. February 3, 2022

Jing Huang et al. Selenium Status and Its Antioxidant Role in metabolic Diseases. Oxidative Medicine and Cellular Longevity. 2022

Malene Outzen el at. The Effect on Selenium Concentration of a Randomized Intervention With Fish and Mussels in a Population with Relatively Low Habitual Dietary Selenium Intake. Nutrients 2015