The Impact of Omega-3 Fatty Acids, Polyphenols and Vitamin D on Neurodegenerative Diseases: A Meta-Analysis

Abstract

Aim: This study is aimed to to assess the impact of vitamin D, omega-3 fatty acids (ω-3), and polyphenols on cognitive functioning, clinical outcomes, and inflammatory biomarkers in patients diagnosed with Alzheimer’s disease (AD), Parkinson’s disease (PD), and Multiple Sclerosis (MS). Method: A systematic search was conducted in the PubMed, Scopus, and Google Scholar databases. Only clinical trials and randomized controlled trials (RCTs) were included. A total of 689 studies published between 2000 and 2025 were reviewed, and 14 studies that met the inclusion criteria were analyzed. Effect sizes were calculated using Hedges’ g value. Fixed and random effects models were used depending on heterogeneity. Funnel plots were used to assess publication bias. All statistical analyses were performed using the Comprehensive Meta-Analysis (CMA) program. Results: Vitamin D supplementation significantly raised blood 25-hydroxyvitamin D [25(OH)D] levels (g = 1.589, p< .001). The Mini-Mental State Examination (MMSE) showed no significant cognitive effects of omega-3 polyunsaturated fatty acids and polyphenols (p> 0.05). One study indicated that ellagic acid reduced Expanded Disability Status Scale (EDSS) scores, while vitamin D and omega-3 supplementation did not. Some studies showed considerable reductions in IL-6 and TNF-α levels, but the meta-analysis found no statistical significance. A substantial decrease in TNF-α was seen in the fixed effects model (p= .0029), but not in the random effects model (p= .132) Conclusion: Vitamin D supplementation markedly elevated serum 25(OH)D levels, indicating its potential as an effective intervention in neurodegenerative processes. The impact of omega-3 fatty acids and polyphenols on cognitive and clinical outcomes was observed to be inconsistent. Additional high-quality, long-term randomized controlled trials are necessary to more accurately assess the clinical efficacy of these compounds in neurodegenerative diseases.

Keywords

• Vitamin D
• omega-3 fatty acids
• polyphenols
• neurodegenerative diseases
• meta-analysis

Omega-3 Yağ Asitleri, Polifenoller ve D Vitaminin Nörodejeneratif Hastalıklar Üzerindeki Etkisi: Bir Meta-Analiz

Öz

Amaç: Bu çalışmanın amacı, Alzheimer hastalığı, Parkinson hastalığı ve Multipl Skleroz tanısı almış bireylerde D vitamini, omega-3 yağ asitleri ve polifenollerin bilişsel fonksiyonlar, klinik sonuçlar ve inflamatuar biyobelirteçler üzerindeki etkilerini değerlendirmektir. Yöntem: Scopus, PubMed ve Google Scholar veri tabanlarında sistematik bir arama yapıldı. Sadece klinik çalışmalar ve randomize kontrollü çalışmalar dahil edildi. 2000 ile 2025 yılları arasında yayınlanan toplam 689 çalışma incelendi ve dahil etme kriterlerini karşılayan 14 çalışma analiz edildi. Etki büyüklükleri Hedges’g değeri kullanılarak hesaplandı. Heterojenliğe bağlı olarak sabit ve rastgele etkiler modelleri kullanıldı. Yayın yanlılığını değerlendirmek için huni grafikleri kullanıldı. Tüm istatiksel analizler Comprehensive Meta-Analysis (CMA) programı kullanılarak yapılmıştır. Bulgular: D vitamini takviyesi, kan 25-hidroksivitamin D [25(OH)D] seviyelerini önemli ölçüde yükseltti (g=1,589, p<,001). Mini-Mental Durum Testi, omega-3 çoklu doymamış yağ asitleri ve polifenollerin bilişsel açıdan önemli bir etkisini göstermedi (p>0,05). Bir çalışma, ellajik asidin Genişletilmiş Engellilik Durumu Ölçeği puanlarını düşürdüğünü, ancak D vitamini ve omega-3 takviyesinin düşürmediğini göstermiştir. Bazı çalışmalar IL-6 ve TNF-α seviyelerinde önemli düşüşler gösterdi, ancak meta-analiz istatiksel olarak anlamlı sonuç bulunamadı. Sabit etkiler modelinde TNF-α’da önemli bir azalma görülürken (p=,0029), rastgele etkiler modelinde görülmemiştir (p=,132). Sonuç: D vitamini takviyesi serum 25(OH)D düzeylerini belirgin şekilde yükseltmiş, bu da nörodejeneratif süreçlerde etkili bir müdahale olarak potansiyelini göstermektedir. Omega-3 yağ asitlerinin ve polifenollerin bilişsel ve klinik sonuçlar üzerindeki etkisinin tutarsız olduğu gözlemlenmiştir. Bu bileşiklerin nörodejeneratif hastalıklardaki klinik etkinliğini daha doğru bir şekilde değerlendirmek için daha fazla, yüksek, kaliteli ve uzun vadeli randomize kontrollü çalışmalara ihtiyaç vardır.

Anahtar Kelimeler

• D vitamini
• omega-3 yağ asitleri
• polifenoller
• nörodejeneratif hastalıklar
• meta-analiz

Kaynakça

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