Table 4.
Association between vitamin D supplementation and cognitive function.
| Study | Design | Mean Follow-Up | Country | Sample Size | Average Age (Year) | Sex Male/Female (%) |
Intervention | Main Results |
|---|---|---|---|---|---|---|---|---|
| Jia J et al. [93] | RCT | 12 months | China | 210 | 68.0 ± 5.9 | 45/55 | Patients received 800 IU/day of vitamin D. | The FSIQ and cognitive test score were significantly higher in the intervention group than in the control group (p < 0.001). |
| Bischoff-Ferrari HA et al. [92] | RCT | 3 years | Switzerland | 2157 | 74.9 | 38.3/61.7 | 2000 IU/day of vitamin D3, 1 g/day of omega-3 strength-training exercise program. | Among adults aged 70 years or older, treatment with vitamin D3, omega-3, or a strength-training exercise program did not result in statistically significant differences in improving cognitive function. |
| Zajac IT et al. [90] | RCT | 6 months | Australia | 436 | 60–90 | 48.4/51.6 | 600 IU/day of vitamin D3 | No effect. |
| Yang T et al. [94] | RCT | 12 months | China | 183 | 67.2 ± 6.1 | 46/54 | 800 IU/day of vitamin D3 | The ANOVA showed improvements in the FSIQ, information, digit span, vocabulary, block design, and picture arrangement scores in the vitamin D group over the placebo group (p < 0.001). |
| Byrn MA et al. [99] | RCT | 12 weeks | USA | 206 | 55.71 | 17/83 | Administration of either weekly vitamin D3 supplementation (50,000 IU) or 5000 IU cholecalciferol once a week. | No significant differences in cognitive outcomes between participants who received high-dose therapy and those who received low dose. |
| Castle M et al. [95] | RCT | 1 year | USA | 138 | 58 ± 6 | 100% female | Vitamin D3 supplementation (600, 2000, or 4000 IU/day). | The CANTAB test results indicated that the 2000 IU/d group, when compared to other groups, performed better in PAL test parameters (p < 0.05). RTI was slower in the 4000 IU/d compared to 600 IU/d group for the 5-choice test (p < 0.01). |
| Jorde R et al. [91] | RCT | 4 months | Norway | 422 | 52 | 52.9/47.1 | Vitamin D 100,000 IU administered as a bolus dose followed by 20,000 IU per week versus placebo. | Vitamin D supplementation did not improve cognitive function during a four-month intervention. |
| Ghaderi A et al. [96] | RCT | 24 weeks | Iran | 64 | 59.2 ± 11.3 | 53/47 | Administration of either 50,000 IU vitamin D supplements (n = 32) or placebo (n = 32) every 2 weeks. | Subjects who were administered vitamin D had a significant reduction in IGT (β −6.25; 95% CI, −8.60 to −3.90; p < 0.001), and significant increases in VFT (β 2.82; 95% CI, 0.78–4.86; p = 0.007), immediate LM (β 1. 32; 95% CI, 0.27–2.37; p = 0.01), reverse DGS (β 2.06; 95% CI, 1.18–2.94; p < 0.001) and VWM (β 0.75; 95% CI, 0.33–1.16; p = 0.001). |
| Schietzel S et al. [98] | RCT | 2 years | Switzerland | 273 | 70.3 | 46.5/53.5 | 2000 or 800 IU vitamin D3/day | No effect. |
| Beauchet O et al. [100] | RCT | 3 months | Canada | 40 | ≥65 | 100% female | Fortified yogurt (400 IU vitamin D and 800 mg calcium). | Fortified yogurts with vitamin D and calcium maintained global cognitive performance (MMSE score (p = 0.022). Global cognitive performance decreased in the control group. |
| Owusu JE et al. [101] | RCT | 3 years | USA | 260 | 68.2 ± 4.9 | 100% female | Adminsitration of vitamin D (adjusted to achieve a serum level > 30 ng/mL) with calcium (diet and supplement total of 1.200 mg) | There is no evidence that vitamin D intakes above the recommended daily allowance are needed to prevent cognitive decline in this population. |
| Hu J et al. [97] | RCT | 12 months | China | 181 | 67.22 ± 6.1 | 44.5/55.5 | Administration of 800 IU/day of vitamin D. | The mean scores of information, DGS, vocabulary, block design and picture arrangement tests in the vitamin D3 group were significantly higher than that in the placebo group both before and after adjustment. In addition, the performance of FIQ (p < 0.001, d = 0.70), VIQ (p < 0.001, d = 0.77) and PIQ (p < 0.001, d = 0.70) was consistent with the five subtests mentioned above. |
| Macpherson H et al. [102] | RCT | 6 months | Australia | 147 | 70.2 ± 6.1 | 30/70 | Daily vitamin D (1000 IU) and omega-3 (900 mg EPA, 600 mg DHA) and protein (20 g) supplementation. | There were no significant between-group differences in cognition at 6 or 12 months. |
DHA: docosahexaenoic acid; EPA: Eicosapentaenoic acid; FSIQ: full scale intelligence quotient; PAL: Paired Associates Learning; RTI: reaction time; IGT: Iowa Gambling Task; VFT: Verbal Fluency Test; LM: Logic Memory; DGS: Digit Span; VWM: visual working memory; FIQ: full IQ; VIQ: verbal IQ; PIQ: performance IQ.