本文探讨了维生素D的剂量与功效问题，作者Ben Hoffman 认为维生素D在骨骼以外还有其他重要作用，例如预防癌症和心血管疾病。他认为许多研究对维生素D的功效持否定态度，是因为剂量不足，并以狩猎采集者的维生素D合成量为例，推断出每日8000IU的维生素D补充量可能更接近人类进化史上的自然水平。作者还批判了将维生素D与癌症和死亡率联系起来的观测性研究，认为其结果不可靠，并强调随机对照试验的重要性。

🤔 作者Ben Hoffman认为许多研究对维生素D的功效持否定态度，是因为剂量不足，他认为大多数人对维生素D的功效持怀疑态度，是因为他们对维生素D的研究存在误解，而没有认真调查。

☀️ 作者以狩猎采集者的维生素D合成量为例，推断出每日8000IU的维生素D补充量可能更接近人类进化史上的自然水平。他认为，在人类进化过程中，狩猎采集者经常在阳光下活动，每天的维生素D合成量可能高达32,000IU。

🧪 作者认为，在研究维生素D的功效时，应该注重随机对照试验，因为观测性研究的结果不可靠。他指出，许多研究中使用的维生素D剂量过低，例如，一些研究中使用的维生素D剂量仅为每天400IU，相当于每天5分钟的快走。

💪 作者认为，维生素D的补充剂量应该根据个人的情况和需求进行调整。他建议，每天补充16,000IU的维生素D可能是一个比较合理的剂量，因为在达到一定剂量后，阳光会产生其他有益的物质，而补充剂量则无法完全替代阳光照射。

🚫 作者还指出，许多研究中使用的维生素D剂量过低，例如，一些研究中使用的维生素D剂量仅为每天400IU，相当于每天5分钟的快走。他认为，这些研究结果并不能说明维生素D没有功效，而是因为剂量不足。

📈 作者认为，维生素D的功效应该根据不同的指标进行评估，例如，骨骼健康、癌症预防、心血管疾病预防等。

🧐 作者认为，维生素D的研究还存在许多争议，需要更多的研究来证实维生素D的功效。

🧐 作者认为，维生素D的研究还存在许多争议，需要更多的研究来证实维生素D的功效。

https://astralcodexten.substack.com/p/contra-hoffman-on-vitamin-d-dosing

[epistemic status: pretty uncertain about each individual fact, moderate confidence in general overview]

I. Hoffman Contra Me

I’ve said many times that (to a first approximation) Vitamin D is a boring bone-related chemical. Most claims that it does exciting things outside of bones - cure COVID! prevent cancer! decrease cardiovascular risk! - are hype, and have failed to stand up to replication.

Ben Hoffman disagrees, and writes How To Interpret Vitamin D Dosage Using Numbers. I’m compressing his argument for space reasons; read the link to check if I’m still being fair:

I am sick of people rejecting good evidence about vitamin D because they are confused about the bad evidence and can't be bothered to investigate, so I am going to explain it […]

Hunter-gatherers in the environment where most of our evolution happened might have been outside all day shirtless. On average the sun's halfway from peak, so that might be equivalent to 8 hours of peak sunlight at the equator. [A study shows people in these conditions synthesize 400 IU of Vitamin D/5 minutes, which comes out to] 8000 IU per hour is 32,000 IU (800 micrograms) per day by this estimate.

When deciding how much is actually appropriate to supplement, we need to take into account diminishing returns; eventually the sunlight starts producing other secondary metabolites which are also good for us, so a 16,000 IU supplement is lower-quality than sunlight but similar in the effective dosage of the most important chemical our evolutionary ancestors' bodies would have made from sunlight; in practice I wouldn't take more than that.

Now let's look at the object-level studies that Scott Alexander says show that vitamin D doesn't work. I'm just going to look at the randomized controlled trials because observational studies for or against vitamin D are trash for anything except hypothesis generation unless they have a very carefully selected instrumental variable.

The colon cancer link is broken but the breast cancer study reports a dosage of 400 IU/day. On the exercise scale that's FIVE MINUTES of brisk walking. FIVE MINUTES is not very long at all compared with FOUR HOURS. [An all-cause mortality study used a thrice-yearly dosing] that amounts to about 800 IU/day, or ten minutes of brisk walking on the exercise scale. [Other studies that found no effect of Vitamin D also used doses around this range].