In the Swedish KiSel-10 clinical trial, the study participants had an average age of 78 years at the start of the study [Alehagen 2013]. Their serum selenium concentration at baseline was at a deficiency level (mean: 67.1 mcg/L).
Moreover, the low selenium status of the elderly Swedish citizens was significantly associated with relatively high mortality risk [Alehagen 2016]. Daily supplementation with 200 mcg of a selenium-enriched yeast preparation together with 200 mg of Coenzyme Q10 raised the study participants’ serum selenium levels to 210 mcg/L and reduced the risk of cardiovascular mortality [Alehagen 2022a].
The four years of joint supplementation were associated with the following positive health outcomes:
- Reduced risk of death from heart disease
- improved health-related quality of life
- decreased inflammation and oxidative stress
- less attrition of telomere length
- anti-aging effects
These positive physical health outcomes raise the question: can selenium supplementation of elderly individuals with low selenium status slow down and delay cognitive decline?
Selenium Supplementation and Cognitive Function
The following points about selenium are important:
- Selenium from the diet and from supplements crosses the blood-brain barrier. In times of low selenium intake, delivery of selenium to the brain takes priority over delivery of selenium to other organs. That shows how important selenium is to the brain and nervous system [Schomburg 2022].
- A KiSel-10 sub-study analysis has shown that selenium supplementation improves the kidney function of selenium-deficient individuals. Selenium supplementation of individuals with impaired kidney function improves cognition [Alehagen 2020b].
- Chronic systemic inflammation is associated with poor cognitive function. KiSel-10 sub-study data show that that supplemental selenium can reduce the level of systemic inflammation and may improve cognitive functioning [Alehagen 2018].
The French Study
In a nine-year cohort study of French citizens aged 60-71 years, researchers observed that selenium status played a role in cognitive functioning [Akbaraly 2007]:
- Cognitive decline increased as plasma selenium levels declined over time.
- The greater the decrease in plasma selenium concentrations, the more likely it was that there would be cognitive decline.
- There exists an association between selenium status and cognitive functioning in elderly people that selenium supplementation possibly can prevent or delay.
The Chinese Study
In a cross-sectional survey of Chinese citizens aged 65 years or older, Gao et al observed that selenium status was relevant for cognitive functioning [Gao 2007]:
- Lower selenium concentrations in nail samples and lower cognitive test scores were significantly associated with one another.
- Low selenium intakes and status over a lifetime were significantly associated with lower cognitive function.
The Italian Study
In Italy, researchers studied men and women with an average age of 75 years. The study participants had plasma selenium concentrations, on average, of 74.5 mcg/L, just above the deficiency levels of 70 mcg/L [Shahar 2010]:
- The low plasma selenium levels were significantly associated with signs of neurological impairments, e.g., worsening coordination.
- The poorer coordination occurred in both upper and lower extremities.
Meta-Analysis of Selenium Supplementation Studies
A 2022 meta-analysis of six studies of solo selenium supplementation showed the following relationships [Pereira 2022]:
- Selenium supplementation resulted in improvement in selenium levels, glutathione peroxidase activity, and in cognitive test scores in patients with mild cognitive impairment.
- Selenium supplementation resulted in improvement in selenium levels and in mini-mental test scores in patients diagnosed with Alzheimer’s disease.
- Selenium supplementation is a good therapy for patients with mild cognitive impairment and with Alzheimer’s disease.
- The beneficial effect of selenium supplementation on cognitive function may come from the antioxidant activity of selenoproteins, i.e., from the activity of the glutathione peroxidases in reducing oxidative stress in the brain.
Conclusion: Link Between Selenium and Cognitive Functioning
Supplementation with a selenium-enriched yeast preparation is associated with various anti-aging effects [Alehagen 2023].
There is accumulating clinical evidence that low selenium status is associated with increased risk of cognitive decline and impairment.
Not all selenium supplements are manufactured to the same standards. It is important to purchase products with documented quality. Selenium-enriched yeast products seem more likely to combat the detrimental effects of oxidative stress [Richie 2014].
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The information provided in this review article is not intended as medical advice. It should not be used as such.
15 February 2024