随着9月23日秋分后北半球日照减少，维生素D补充剂再次迎来消费热潮。发表于2017年的一项研究显示，在2013-2014年间，有18%的美国人服用大剂量维生素D补充剂，而在1999-2000年这一比例仅为0.3%，全美每年进行的维生素D血液检测更超过1,000万次，且获得了英国和冰岛等国政府的官方推荐。医学界自一个世纪前便确立了维生素D对防治佝偻病的核心作用，随后在全身各器官发现其受体；1980年代的流行病学研究进一步发现美国北部各州的多种癌症死亡率显著高于阳光充足的南部，动物实验亦显示其能抑制癌细胞生长，令外界对其防癌及抗感冒功效寄予厚望。

然而，严格的大规模人体临床试验证实了这些理论假说的破灭。涵盖数万名受试者并持续跟踪多年的三大顶级随机对照试验——美国的VITAL研究、澳大利亚的D-Health试验以及新西兰的ViDA研究，均未发现补充维生素D带来任何统计学上的显著健康收益。2022年发表在《新英格兰医学杂志》（NEJM）上的一篇权威述评明确指出，大剂量补充维生素D不仅未能降低癌症发病率或改善心脏健康，也无法预防跌倒、提升大脑认知或预防冬季感冒；即便在被诊断为轻度缺乏的人群中，它也未显示出任何保护作用，甚至未能降低常见骨折的发生风险。

这一研究反差表明，生化假说无法替代扎实的随机临床验证，人体生理机制远比理论推导复杂。目前的科学共识认为，维持人体基本的维生素D生理阈值是必要的，但盲目额外补充毫无益处。除生活在高纬度极寒地区、深肤色、长期室内工作且无法通过鱼类、蛋类和红肉等膳食摄入足够营养的高危人群可在最黑暗的冬季月份适当补充外，对于广大普通健康人群而言，耗费巨资购买维生素D补充剂和进行频繁血液筛查完全是不必要的浪费。

As daylight hours contract following the autumn equinox on September 23rd, consumer interest in vitamin D supplements surges. A landmark 2017 study documented that 18% of Americans took high-dose vitamin D supplements in 2013-14, skyrocketing from just 0.3% in 1999-2000, while over 10m diagnostic blood tests are administered annually in America alongside official government endorsements in Britain and Iceland. Historical medical consensus established a century ago that vitamin D prevents rickets, while subsequent discoveries of cellular receptors throughout the body bolstered therapeutic optimism. Influential 1980s epidemiological studies observed substantially higher cancer mortality in cloudy northern American states than in sunny southern ones, with animal models demonstrating tumour-inhibiting effects and spurring widespread belief in immune enhancement.

Despite rigorous preclinical rationale, massive randomised clinical trials involving tens of thousands of participants over multiple years—notably America’s VITAL study, Australia’s D-Health trial, and New Zealand’s ViDA study—demonstrated no measurable clinical benefits. A definitive 2022 editorial published in the New England Journal of Medicine concluded that supplemental vitamin D neither reduced cancer risks nor improved cardiovascular outcomes, cognitive faculties, falls, or respiratory infections. Crucially, the intervention failed to lower fracture incidence—even among individuals diagnosed with mild deficiency—directly debunking the prevailing hypothesis that pharmacological supplementation beyond baseline nutritional requirements confers prophylactic skeletal or systemic protection.

These empirical refutations underscore that biological plausibility cannot substitute for gold-standard human clinical trials, as intricate metabolic feedback systems resist simplistic micronutrient therapies. Contemporary clinical consensus emphasizes that while baseline sufficiency is vital to avoid clinical deficiency, excess intake provides zero marginal utility. Except for high-risk demographics during winter months—such as dark-skinned individuals or indoor workers residing in extreme northern latitudes whose diets lack fish, eggs, and red meat—routine high-dose supplementation and indiscriminate blood screening remain an unjustifiable, costly expenditure for the general public.

Source: Consuming extra vitamin D is less good than it sounds

Subtitle: What works well in theory seems not to in practice

Dateline: Sep 24th 2026\n