Effects of Brazil nut consumption on selenium status and cognitive performance in older adults with mild cognitive impairment: a randomized controlled pilot trial
Oxidative stress is closely related to cognitive impairment, and the antioxidant system may be a potential therapeutic target to preserve cognitive function in older adults. Selenium plays an important antioxidant role through selenoproteins. This controlled trial aimed to investigate the antioxidant and cognitive effects of the consumption of Brazil nuts, the best selenium food source.
We enrolled 31 older adults with mild cognitive impairment (MCI) who were randomly assigned to ingestion of Brazil nuts or to the control group. Participants of the treatment group consumed one Brazil nut daily (estimated 288.75 µg/day) for 6 months. Blood selenium concentrations, erythrocyte glutathione peroxidase (GPx) activity, oxygen radical absorbance capacity, and malondialdehyde were evaluated. Cognitive functions were assessed with the CERAD neuropsychological battery.
Eleven participants of the treated group and nine of the control group completed the trial. The mean age of the participants was 77.7 (±5.3) years, 70 % of whom were female. We observed increased selenium levels after the intervention, whereas the control group presented no change. Among the parameters related to the antioxidant system, only erythrocyte GPx activity change was significantly different between the groups (p = 0.006). After 6 months, improvements in verbal fluency (p = 0.007) and constructional praxis (p = 0.031) were significantly greater on the supplemented group when compared with the control group.
Our results suggest that the intake of Brazil nut restores selenium deficiency and provides preliminary evidence that Brazil nut consumption can have positive effects on some cognitive functions of older adults with MCI.
KeywordsBrazil nuts Selenium Oxidative stress Mild cognitive impairment
Conflict of interest
The authors declare that they have no conflict of interest.
The research protocol was approved by the Research Ethics Committee of the Faculdade de Ciências Farmacêuticas da Universidade de São Paulo and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All participants gave their informed consent prior to their inclusion in the study.
- 11.Thomson CD, Chisholm A, McLachlan SK et al (2008) Brazil nuts: an effective way to improve selenium status. Am J Clin Nutr 87:379–384Google Scholar
- 15.Leszek J, Inglot AD, Janusz M et al (1999) Colostrinin®: a proline-rich polypeptide (PRP) complex isolated from ovine colostrum for treatment of Alzheimer’s disease. A double-blind, placebo-controlled study. Arch Immunol Ther Exp (Warsz) 47:377–384Google Scholar
- 17.Kesse-Guyot E, Fezeu L, Jeandel C et al (2011) French adults’ cognitive performance after daily supplementation with antioxidant vitamins and minerals at nutritional doses: a post hoc analysis of the Supplementation in Vitamins and Mineral Antioxidants (SU.VI.MAX) trial. Am J Clin Nutr 94:892–899CrossRefGoogle Scholar
- 22.Association of Official Analytical Chemists (AOAC) (1990) Official methods of analysis. AOAC, WashingtonGoogle Scholar
- 24.Friedewald WT, Levy RI, Fredrickson DS (1972) Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 18(6):499–502Google Scholar
- 25.Paglia DE, Valentine WN (1967) Studies on the quantitative and qualitative characterization of erythrocyte gluthatione peroxidase. J Lab Clin Med 70:158–169Google Scholar
- 29.Cohen J (1988) Statistical power analysis for the behavioral sciences, 2nd edn. Erlbaum, HillsdaleGoogle Scholar
- 34.De la Monte SM, Tong M, Lester-Coll N et al (2006) Therapeutic rescue of neurodegeneration in experimental type 3 diabetes: relevance to Alzheimer’s disease. J Alzheimers Dis 10:89–109Google Scholar
- 39.Bellinger FP, He QP, Bellinger MT et al (2008) Association of selenoprotein P with Alzheimer’s pathology in human cortex. J Alzheimers Dis 15(3):465–472Google Scholar
- 40.Takemoto AS, Berry MJ, Bellinger FP (2010) Role of selenoprotein P in Alzheimer’s disease. Ethn Dis 20(Suppl 1):92–95Google Scholar
- 41.Garcia T, Esparza JL, Nogues MR et al (2009) Oxidative stress status and RNA expression in hippocampus of an animal model of Alzheimer’s disease after chronic exposure to aluminum. Hippocampus 20:218–225Google Scholar
- 43.Loef M, Schrauzer GN, Walach H (2011) Selenium and Alzheimer’s disease: a systematic review. J Alzheimers Dis 26:81–104Google Scholar
- 45.IOM - Institute of Medicine (2002) Dietary reference intakes for vitamin C, vitamin E, selenium, and carotenoids Washington. The National Academy Press, WashingtonGoogle Scholar
- 54.Pires LV, Silva AMDO, Alencar LL, Pimentel JA, Mancini-Filho J, Cozzolino SM (2011) Investigação da concentração de selênio e dos compostos fenólicos presentes na castanha-do-brasil (Bertholletia excelsa H.B.K.) e sua atividade antioxidante in vitro. Nutrire 36s:7sGoogle Scholar
- 63.Baldeiras I, Santana I, Proença MT et al (2008) Peripheral oxidative damage in mild cognitive impairment and mild Alzheimer’s disease. J Alzheimer’s Dis 15:117–128Google Scholar
- 65.Torres LL, Quaglio NB, Souza GT et al (2011) Peripheral oxidative stress biomarkers in mild cognitive impairment and Alzheimer’s disease. J Alzheimer’s Dis 26(1):59–68Google Scholar
- 71.Mutter J, Curth A, Naumann J et al (2010) Does inorganic mercury play a role in Alzheimer’s disease? A systematic review and an integrated molecular mechanism. Bouvé Fac Pub 22:357–374Google Scholar