下面的各種研究有點反直覺. 民眾服用維生素是希望減少某些疾病. 結果可能與我們想像的截然不同. 多年之前曾看過文獻. 長期服用維生素會增加死亡率
研究團隊與國衛院高齡醫學暨健康福祉研究中心的許志成執行長合作，利用台灣健保資料庫進行分析，發現未罹患失智症的年長者若每年服用活性維生素D3(calcitriol)超過146天，其日後發生失智症風險是未服用者的1.8倍。若失智症患者每年服用維生素D3超過146天，其死亡風險是未服用者的2.17倍。
但在uptodate裡面的相關資料跟上面的矛盾.
uptodate 認知能力下降和失智症的風險因素
維生素D缺乏症
有證據表明，維生素D缺乏與老年人的認知障礙和阿茲海默症有關[ 2,298 ]。但這種影響似乎較小，其臨床意義尚不清楚。
一項基於人群的橫斷面研究發現，維生素D缺乏的老年女性認知評分低於維生素D充足的女性[ 299 ]；而另一項研究則發現，維生素D攝取量達到建議水準的女性認知評分高於攝取不足的女性[ 300 ]。其他橫斷面研究和病例對照研究發現，維生素D水平低的患者白質高訊號和梗塞體積較大，且有全因失智症[ 301 ]或阿茲海默症[ 302 ]的風險較高（2.0倍）。
一項基於人群的橫斷面研究發現，維生素D缺乏的老年女性認知評分低於維生素D充足的女性[ 299 ]；而另一項研究則發現，維生素D攝取量達到建議水準的女性認知評分高於攝取不足的女性[ 300 ]。其他橫斷面研究和病例對照研究發現，維生素D水平低的患者白質高訊號和梗塞體積較大，且有全因失智症[ 301 ]或阿茲海默症[ 302 ]的風險較高（2.0倍）。
不過補充維生素D也有益處. 例如會減少某些癌症
前瞻性隊列研究的結果並不一致。一項針對1604名老年男性進行平均4.6年追蹤的前瞻性研究發現，維生素D水平與同時發生的或新發的癡呆症之間均無顯著相關性[ 303 ]。相較之下，一項針對858名65歲以上成年人進行的隊列研究發現，在為期六年的觀察期內，低維生素D水平與認知能力下降相關[ 304 ]。另一項針對1658名老年人進行平均5.6年追蹤的研究表明，與維生素D充足狀態相比，嚴重維生素D缺乏（<25 nmol/L）與全因失智症和阿茲海默症的相對風險（RR）升高約兩倍相關[ 305 ]。
前瞻性隊列研究的結果並不一致。一項針對1604名老年男性進行平均4.6年追蹤的前瞻性研究發現，維生素D水平與同時發生的或新發的癡呆症之間均無顯著相關性[ 303 ]。相較之下，一項針對858名65歲以上成年人進行的隊列研究發現，在為期六年的觀察期內，低維生素D水平與認知能力下降相關[ 304 ]。另一項針對1658名老年人進行平均5.6年追蹤的研究表明，與維生素D充足狀態相比，嚴重維生素D缺乏（<25 nmol/L）與全因失智症和阿茲海默症的相對風險（RR）升高約兩倍相關[ 305 ]。
Vitamin D deficiency — There is some evidence that vitamin D deficiency is associated with cognitive impairment and AD in older adults [2,298]. The effect appears to be small and of uncertain clinical significance.
A population-based cross-sectional study of older women found that those with vitamin D deficiency had lower cognitive scores compared with those without deficiency [299], while another found that women with vitamin D intake at the recommended level had higher cognitive scores compared with those with inadequate intake [300]. Other cross-sectional and case-control studies have found that patients with low vitamin D levels have higher volumes of white matter hyperintensities and infarctions as well as higher odds (2.0) of all-cause dementia [301] or AD specifically [302].
Prospective cohort series have been less consistent. One prospective study that followed 1604 older men for a mean 4.6 years found no significant relationship between vitamin D status and either concurrent or incident dementia [303]. By contrast, low levels of vitamin D were associated with cognitive decline over a six-year observation period in a cohort of 858 adults over 65 years [304]. In another study involving 1658 older adults followed for a mean of 5.6 years, severe vitamin D deficiency (<25 nmol/L) was associated with an approximately twofold higher RR of both all-cause dementia and Alzheimer dementia compared with a vitamin D replete state [305].
「美國醫學會期刊網」（JAMA Network）。
2024年6月，美國的國家癌症研究所（NCI）8 年(1993-2001)的追蹤調查，計畫包含了39萬124名健康成年人，團隊追蹤這些受試者日常服用綜合維生素的使用情形，並分析這些人的三項主要健康研究數據。
研究結果.
每日服用多種維生素不能降低死亡的風險
每日服用多種維生素的受試者，死亡風險反而增加了4%。
Abstract
Importance One in 3 US adults uses multivitamins (MV), with a primary motivation being disease prevention. In 2022, the US Preventive Services Task Force reviewed data on MV supplementation and mortality from randomized clinical trials and found insufficient evidence for determining benefits or harms owing, in part, to limited follow-up time and external validity.
Objective To estimate the association of MV use with mortality risk, accounting for confounding by healthy lifestyle and reverse causation whereby individuals in poor health initiate MV use.
Design, Setting, and Participants
This cohort study used data from 3 prospective cohort studies in the US, each with baseline MV use (assessed from 1993 to 2001), and follow-up MV use (assessed from 1998 to 2004), extended duration of follow-up up to 27 years, and extensive characterization of potential confounders. Participants were adults, without a history of cancer or other chronic diseases, who participated in National Institutes of Health–AARP Diet and Health Study (327 732 participants); Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (42 732 participants); or Agricultural Health Study (19 660 participants). Data were analyzed from June 2022 to April 2024.
Exposure Self-reported MV use.
Main Outcomes and Measures
The main outcome was mortality. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% CIs.
Results
Among 390 124 participants (median [IQR] age, 61.5 [56.7-66.0] years; 216 202 [55.4%] male), 164 762 deaths occurred during follow-up; 159 692 participants (40.9%) were never smokers, and 157 319 participants (40.3%) were college educated. Among daily MV users, 49.3% and 42.0% were female and college educated, compared with 39.3% and 37.9% among nonusers, respectively. In contrast, 11.0% of daily users, compared with 13.0% of nonusers, were current smokers. MV use was not associated with lower all-cause mortality risk in the first (multivariable-adjusted HR, 1.04; 95% CI, 1.02-1.07) or second (multivariable-adjusted HR, 1.04; 95% CI, 0.99-1.08) halves of follow-up. HRs were similar for major causes of death and time-varying analyses.
Conclusions and Relevance In this cohort study of US adults, MV use was not associated with a mortality benefit. Still, many US adults report using MV to maintain or improve health.
