Table 3.
Association between vitamin C and antioxidant supplementation and cognitive function.
| Study | Design | Mean Follow-Up | Country | Sample Size | Average Age (Year) | Sex Male/Female (%) |
Intervention | Main Results |
|---|---|---|---|---|---|---|---|---|
| Sim M et al. [82] | RCT | 4 weeks | Republic of Korea | 214 | 20–39 | 39.3/60.7 | 500 mg vitamin C twice a day. | Vitamin C supplementation notably increased attention and work absorption (p = 0.03), with a clear tendency towards fatigue improvement. |
| Morató X et al. [86] | RCT | 12 months | Spain | 50/50 | 73.1 ± 7.5 | 40/60 | Standardized extract of Ginkgo biloba EGb 761 240 mg tablets were given orally. | No significant differences between groups in MMSE, CDR, NBACE scores, or amnestic profile; higher scores in irritability/lability parameter (p = 0.006) and BDS (p = 0.048) in control group. |
| Thaung Zaw JJ et al. [80] | RCT | 24 months | Australia | 125 | 45–85 | 100% female | 75 mg trans-resveratrol or placebo per day. | Resveratrol supplementation led to 33% improvement in overall cognitive performance (Cohen’s d = 0.170, p = 0.005). |
| Lai S et al. [84] | RCT | 6 months | Italy | 59 | 45.1 ± 10.7 | 55.9/44.1 | ALA 1.6 g/day. | BDI-II, HAM-D, MMSE tests showed significant improvement (p = 0.007, p < 0.001, p < 0.001) in patients treated with ALA compared to control group. |
| Foroumandi E et al. [81] | RCT | 4 months | Iran | 82 | 72.0 ± 2.5 | 34.1/65.9 | Intervention group patients received 500 mg dry extract (5 cc) of fenugreek seed extract. | Positive effects on memory (p < 0.001), quality of life (p < 0.001) and selective oxidative index level. |
| Baker LD et al. [87] | RCT | 3 years | USA | 2262 | 73.0 | 40/60 | Daily administration of cocoa extract (containing 500 mg/day flavanols) versus placebo. | Cocoa extract had no effect on global cognition (mean z-score = 0.03, 95% CI: −0.02–0.08; p = 0.28). |
| Bell L et al. [88] | RCT | 12 weeks | UK | 60 | 18–30 | 10/90 | 400 mg of GSPE extract daily. | 400 mg of GSPE did not consistently improve cognitive function in healthy young adults. |
| Stringham NT et al. [83] | RCT | 6 months | Greece | 59 | 18–25 | 45.7/54.3 | Carotenoids lutein and zeaxanthin, along with the zeaxanthin isomer meso-zeaxanthin (13 mg/day or 27 mg/day total). | For cognitive measures, all scores for composite memory, verbal memory, sustained attention, psychomotor speed, and processing speed improved significantly in treatment groups (p < 0.05 for all) and remained unchanged in the placebo group. |
| Yoon J et al. [85] | RCT | 12 weeks | Japan | 36 + 36 | 69.5 ± 7.6 | 47/53 | Participants received 3 g of DOTP or placebo in olive oil twice daily for 12 weeks. | Among cognitive domains, complex attention had a significant time × group interaction effect (p = 0.049) between the DOTP and placebo groups. Time effects were significant (p < 0.05) for psychomotor speed, reaction time, cognitive flexibility, processing speed, and executive function domains. |
| Hashimoto M et al. [89] | RCT | 12 months | Japan | 44 | 70.2 ± 1.4 | 52.4/47.6 | Randomized participants in the PO group received soft gelatin capsules containing 1.47 mL of PO daily, and those in the PO + POPP group received soft gelatin capsules containing both 1.47 mL of PO and 1.12 g PP daily. | At the end of intervention, the POPP group showed significantly higher cognitive index scores than the PO group, POOP may improve age-related cognitive impairment in healthy elderly people. |
ALA: alpha lipoic acid; BDI-II: Beck Depression Inventory-II; BDS: Blessed Dementia Scale; CDR: clinical dementia rating; DOTP: desert olive tree pearl; GSPE: grape seed polyphenol; HAM-D: Hamilton Depression Rating Scale; MMSE: Mini-Mental State Examination; PO: Perilla frutescens seed oil; POPP: PO + ponkan powder.