Decades of research have linked vitamin D deficiency with neurological disorders such as multiple sclerosis (MS), Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS). However, the role of vitamin D supplementation in the prevention and management of these conditions is unclear.
A brief overview of the potential mechanisms underlying the association between vitamin D levels and neuropathy is shown in Figure 1.1 Each of these diseases has a unique relationship with vitamin D receptors and reactions or processes that are enhanced or mitigated by serum vitamin D levels.1
vitamin D deficiency
Vitamin D was discovered to be a steroid-like hormone in 1968 and later isolated as the active form of vitamin D.3chemically known as 1,25(OH)2D.3.1,2 Vitamin D receptors are found in almost every tissue in the human body, including the brain and throughout the nervous system.2
Laboratory assessment of serum vitamin D levels assesses 25-hydroxyvitamin D [25(OH)D]which is measured in ng/mL and is the sum of both D2 (ergocalciferol) and D3 (cholecalciferol) reflects the total blood content of vitamin D.3
Several medical societies have issued minimum serum concentration recommendations of 25(OH)D, including the American Academy of Medicine (formerly the Institute of Medicine), the Endocrinology Society, the International Osteoporosis Foundation, and the American Geriatrics Society.1 The American Academy of Medicine has set a recommended range of 20-50 ng/mL, but also up to 50 ng/mL, based on an increase in fractures and an increase in pancreatic and prostate cancer at higher doses. Did.Four A vitamin D level of 30 ng/mL is the average recommended by most societies.1 However, guidance on vitamin D supplementation for patients with neurological disorders is lacking.
Vitamin D deficiency is more common among people over the age of 65 living in areas above the 40th parallel and below the 40th parallel south, or in areas with little sunlight and high levels of melanin.3 Sunlight provides about 80% to 90% of your recommended daily vitamin D dose, far more than you can get from a balanced diet.3
Multiple sclerosis is a disease of the central nervous system involving demyelination, neurodegeneration, and chronic inflammation.Five Environmental risk factors have been elucidated in association with MS and include infections (such as Epstein-Barr virus), smoking, inflammation, geography (relative to latitude), climate, and vitamin D deficiency.1,3 Latitude, in particular, is highly correlated with the geographic distribution of MS, with increasing frequency in regions above 40°N and below 40°S.1,3 These regions also had higher rates of vitamin D deficiency, further supporting the correlation between MS and vitamin D deficiency.1,3
Vitamin D supplementation not only prevents the onset of MS, but also appears to help treat the disease by reducing relapse rates.3,5 Some studies have shown potential benefits of supplementation in multiple sclerosis at doses varying from 10,000 to 40,000 IU per day, but other studies have shown no favorable results. Hmm.Five The use of very high doses (e.g., 50,000 to 2.604,000 IU/day) resulting in vitamin D levels of 150 ng/mL or higher is associated with side effects that mimic multiple sclerosis relapse/progression, including muscle weakness. D can lead to toxicity. Neuropsychiatric disorders/psychosis.Five In some cases, irreversible renal damage, arrhythmias secondary to hypercalcemia have been reported.Five
Alzheimer’s disease manifests as progressive cognitive decline with behavioral changes and neurodegeneration secondary to the formation of neurofibrillary tangles and senile plaques.1,6 Randel et al.6 Note that studies on vitamin D and AD date back to 1992 and reported “decreased vitamin D receptor (VDR) mRNA levels in the hippocampus of AD patients.” Conducted an extensive review of 38 human and animal studies on vitamin D and cognitive outcomes, Landel et al. found that vitamin D “may be important in aging and age-related cognitive decline” and that “… It may be associated with an increased risk of developing AD.” Dementia, not the causative agent. ”6
In a large cross-sectional study in Rotterdam, magnetic resonance imaging (MRI) of 2716 participants without dementia showed that those with vitamin D deficiency had a higher hippocampal volume compared to participants with normal vitamin D levels. , showed smaller brain volume, gray matter, and white matter. .7 Results from a large observational study, including prospective data from the UK Biobank on more than 294,500 people (mainly women aged 60 and over), show that participants with low vitamin D levels are more likely to develop dementia than those with normal levels. suggests a 54% higher chance of developing .8
A 6-month pilot study of 43 newly diagnosed Alzheimer’s disease patients found that the use of vitamin D supplementation in combination with memantine was associated with cessation of cognitive decline compared with the use of either intervention alone. was excellent in9 Findings from other studies suggest that vitamin D helps clear amyloid b plaques in vitro.10,11 A randomized, placebo-controlled trial in 210 Alzheimer’s disease patients showed that supplementation with 800 IU of vitamin D per day for 12 months was significantly associated with improvements in amyloid-β-related biomarkers. rice field (P. <.001) and information, arithmetic, digit span, vocabulary, block design, and picture placement scores (P. <.05).12 Significant increases in full-scale IQ scores were also seen (P. <.001).12
Researchers also investigated the potential effects of vitamin D on orientation, memory, cognitive decline, and executive function (as measured by the Mini-Mental Status Examination). [MMSE]) Elderly without Alzheimer’s disease.13,14 A longitudinal study of 1,058 older adults who underwent serum vitamin D testing between 1997 and 1999, followed by three follow-up cognitive tests over 12 years, found that vitamin D deficiency was associated with decreased performance on the MMSE. was associated with13