Effects of Selenium Supplementation in Patients with Mild Cognitive Impairment or Alzheimer’s Disease: A Systematic Review and Meta-Analysis

Nutrients
Q1
Aug 2022
Citations:52
Influential Citations:0
Systematic Reviews / Meta-Analyses
86
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Methods
Adults with Alzheimer's disease or mild cognitive impairment (older adults; age ~68–88). Study designs were randomized controlled trials, including double‑blind, placebo‑controlled, multicenter, and parallel‑group formats, conducted across Brazil, USA, The Netherlands, Germany, Belgium, Spain, Italy, France, UK, Iran, Australia, and others.
Intervention
Se regimens varied: Brazil nut (1 nut daily) for 24 weeks; inorganic Se as sodium selenate at 320 µg/day (three times daily) for 24 weeks; supranutritional sodium selenate at 10 mg/day (three times daily) for 24 weeks; Formulation F ampoule containing 27.5 µg Se daily for 24 weeks; Souvenaid delivering 60 µg Se daily for 24 weeks; probiotic plus selenium delivering selenium ~200 µg/day for 12 weeks; evening primrose oil with zinc sulfate and sodium selenite (EPO/Zn/Se) for 20 weeks.
Results
Selenium supplementation significantly increased selenium levels in plasma (about 4.09x), serum (about 1.88x), erythrocytes (about 3.73x), and CSF (about 2.18x). Erythrocyte GPX activity rose by about 0.95x (p<0.001). Malondialdehyde (MDA) levels increased by about 0.95x (p=0.0002), indicating no reduction in lipid peroxidation with Se alone. Cognitive tests improved in some MCI cases (e.g., verbal fluency and constructive praxis) and in some AD cases (MMSE), with Se plus other nutrients regimens also showing cognitive benefits in AD and MCI, though MMSE/ADAS-Cog improvements were not consistently significant across Se+nutrient trials. Overall, selenium status and GPX activity improved with supplementation, suggesting a potential brain health benefit in AD and MCI; longer-term, standardized trials are needed to confirm cognitive benefits and safety.
Limitations
Small sample sizes; heterogeneity in selenium regimens (dose, form, duration); varied outcome measures and reporting (some medians); risk of bias in several studies; short follow-up limits assessment of long-term cognitive effects and safety.

Abstract

Elevated levels of oxidative stress could cause and aggravate Alzheimer’s disease (AD). Selenium (Se) is a trace element with antioxidant and anti-inflammatory activity with neuroprotective effects. To evaluate the effects of Se supplementation in pa...