巨噬细胞和树突状细胞，这是 D 能参与免疫调节的一条路径皮肤的角质形成细胞乳腺上皮、前列腺、结肠上皮、胎盘甲状旁腺（形成负反馈回路）胰岛的 β 细胞 临床上有几个含义：
它解释了为什么 D 能影响不少看似无关的器官：它在这些组织里就地激活、就地作用，不完全依赖肾脏的中央调控在结节病（sarcoidosis）和某些淋巴瘤里，巨噬细胞的 CYP27B1 失控，活性 D 多到溢进血液，造成血钙升高（高钙血症）。这是维生素 D 中毒之外的另一种高钙原因（CKD）的患者，肾脏的 CYP27B1 减少，全身的 1,25(OH)₂D 偏低，接着出现继发性甲状旁腺功能亢进和骨病。所以临床上用活性 D 类似物（如骨化三醇、帕立骨化醇），而不是普通的 外用治疗银屑病的卡泊三醇（calcipotriol），本身就是一种活性 D 类似物，直接作用于皮肤细胞上的 ，不需要再被活化。
儿童身上对应的是佝偻病（rickets）：骨骼矿化失败，长骨变软、弯曲变形；表现包括 O 形腿或 X 形腿、鸡胸、肋骨上串珠样的隆起、颅骨软，出牙晚、容易蛀。19 世纪工业革命时的伦敦，烟雾加上拥挤的城市公寓，让孩子几乎晒不到太阳，佝偻病在城市儿童里非常普遍，这就是维生素 D 故事的起点：1922 年 McCollum 命名了维生素 D，1930 年代起，强化了维生素 D 的牛奶让佝偻病大幅减少。今天仍然有病例，而且并不罕见：多数是几种风险叠在一起的婴儿，比如皮肤较深、母亲因宗教习俗遮盖大部分皮肤、一家人迁到了高纬度地区，又长期母乳喂养而没有补 D。
成人对应的是骨软化症（osteomalacia）：骨基质矿化不足，双能 X 线检查（）未必能看出来。表现是骨痛、肌无力、应力性骨折。原因不明的全身骨痛、大腿和上臂的肌无力、反复轻伤就骨折，再加上 严重偏低（< 25 nmol/L），就应当想到这个诊断；它很容易被误认为纤维肌痛、抑郁或者老了。
National Institutes of Health, Office of Dietary Supplements. (2024). Vitamin D — Fact Sheet for Health Professionals. Fact sheet (updated June 27, 2025; Wayback snapshot 20 September 2026): 25(OH)D below 30 nmol/L (12 ng/mL) is associated with deficiency, 30 to below 50 nmol/L is generally considered inadequate, 50 nmol/L (20 ng/mL) or more is sufficient for most people, and above 125 nmol/L (50 ng/mL) can be associated with adverse effects; RDA 600 IU (15 mcg) to age 70 and 800 IU (20 mcg) above 70; adult UL 4,000 IU (100 mcg); older people and people with darker skin (more melanin) make less vitamin D from sunlight (fact sheet). ods.od.nih.gov/factsheets/VitaminD-HealthProfessional
Bikle, D. D. (2014). Vitamin D metabolism, mechanism of action, and clinical applications. Chemistry & Biology, 21(3), 319–329. 10.1016/j.chembiol.2013.12.016
Holick, M. F. (2007). Vitamin D deficiency. The New England Journal of Medicine, 357(3), 266–281. 10.1056/NEJMra070553
EFSA Panel on Dietetic Products, Nutrition and Allergies. (2016). Dietary reference values for vitamin D. EFSA Journal, 14(10), 4547. 10.2903/j.efsa.2016.4547
Uwitonze, A. M., & Razzaque, M. S. (2018). Role of magnesium in vitamin D activation and function. Journal of the American Osteopathic Association, 118(3), 181–189. 10.7556/jaoa.2018.037
Institute of Medicine. (2011). Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press. www.ncbi.nlm.nih.gov/books/NBK56070
National Institutes of Health, Office of Dietary Supplements. (2021). Vitamin K — Fact Sheet for Health Professionals. Fact sheet (updated March 29, 2021; Wayback snapshot 19 September 2026): free phylloquinone is about 80% absorbed, but absorption from food is much lower - the body absorbs only 4% to 17% as much from spinach as from a tablet; Table 2: natto, 3 ounces, 850 mcg (as MK-7); egg, hard boiled, 1 large, 4 mcg (as MK-4) (fact sheet). ods.od.nih.gov/factsheets/VitaminK-HealthProfessional
Martineau, A. R., et al. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis. BMJ, 356, i6583. Individual-participant-data meta-analysis of 25 double-blind RCTs (11,321 participants aged 0-95; IPD for 10,933). Overall adjusted OR for acute respiratory infection 0.88 (0.81-0.96). Daily or weekly dosing without boluses OR 0.81 (0.72-0.91); one or more bolus doses OR 0.97 (0.86-1.10), no benefit. Among daily/weekly recipients: baseline 25(OH)D below 25 nmol/L OR 0.30 (0.17-0.53); 25 nmol/L or above OR 0.75 (0.60-0.95). Serious adverse events not increased (OR 0.98) (abstract, PMID 28202713). 10.1136/bmj.i6583
Martineau, A. R., Timms, P. M., Bothamley, G. H., Hanifa, Y., Islam, K., Claxton, A. P., et al. (2011). High-dose vitamin D3 during intensive-phase antimicrobial treatment of pulmonary tuberculosis: a double-blind randomised controlled trial. The Lancet, 377(9761), 242-250. PRIMARY ENDPOINT NULL: median time to sputum culture conversion 36.0 vs 43.5 days, adjusted HR 1.39 (0.90-2.16), p=0.14. The only positive signal is a TaqI tt genotype subgroup. Do not cite it as evidence that vitamin D speeds conversion. 10.1016/S0140-6736(10)61889-2
Girgis, C. M., Clifton-Bligh, R. J., Hamrick, M. W., Holick, M. F., & Gunton, J. E. (2013). The roles of vitamin D in skeletal muscle: form, function, and metabolism. Endocrine Reviews, 34(1), 33–83. 10.1210/er.2012-1012
Bischoff-Ferrari, H. A., Dawson-Hughes, B., Staehelin, H. B., Orav, J. E., Stuck, A. E., Theiler, R., et al. (2009). Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials. BMJ, 339(oct01 1), b3692-b3692. Two separate results: supplemental vitamin D at 700-1000 IU/day cut falls 19% (RR 0.81), and achieved serum 25(OH)D >= 60 nmol/L (24 ng/mL) cut them 23% (RR 0.77). Below either threshold there was no reduction. The story welded the 19% onto the serum threshold and wrote that threshold as 30 ng/mL. 10.1136/bmj.b3692
de Koning, E. J., Lips, P., Penninx, B. W. J., Elders, P. J., Heijboer, A. C., den Heijer, M., et al. (2019). Vitamin D supplementation for the prevention of depression and poor physical function in older persons: the D-Vitaal study, a randomized clinical trial. The American Journal of Clinical Nutrition, 110(5), 1119-1130. The D-Vitaal trial. There is no "Aronson 2021" vitamin-D depression trial; this is the paper that name pointed at. 10.1093/ajcn/nqz141
Owens, D. J., Allison, R., Close, G. L. (2018). Vitamin D and the Athlete: Current Perspectives and New Challenges. Sports Medicine, 48(S1), 3-16. Its position is that vitamin D is a physiological requirement, NOT an ergogenic aid. Athlete muscle-function data are mixed; the strength benefit people quote is seen in adults with 25(OH)D below about 25 nmol/L, largely older adults, not in replete athletes. 10.1007/s40279-017-0841-9
Sanders, K. M., Stuart, A. L., Williamson, E. J., Simpson, J. A., Kotowicz, M. A., Young, D., et al. (2010). Annual High-Dose Oral Vitamin D and Falls and Fractures in Older Women. JAMA, 303(18), 1815. A single ANNUAL oral dose of 500,000 IU in women 70+ (n=2,256) increased falls (IRR 1.15) and fractures (IRR 1.26), with risk highest in the first 3 months. The story attached this result to a monthly 50,000 IU regimen, which is a different dose and a different interval. 10.1001/jama.2010.594