3 ms·

I suspect that blood vitamin D is mainly a marker for how much outdoor exercise people are getting, and that it is the exercise rather than the D which is causa

I suspect that blood vitamin D is mainly a marker for how much outdoor exercise people are getting, and that it is the exercise rather than the D which is causal.

fragmede 4mo ago
But then why do we see improvements in people that get vitamin D + K2 supplements and not exercise?
- amanaplanacanal 4mo ago
  As the article mentions, we pretty much don't see improvements with supplementation.
  - criddell 4mo ago
    From the article: > the balance of evidence tips pretty clearly in the direction that people with low-ish levels would be wise to supplement
  - rzz3 4mo ago
    I don’t think there’s anything definitive. 400IU/day from one study is nothing if you’re deficient. 2000IU from another study is better, but even then we don’t seem to know much about absorption from these studies. For example, did it actually raise serum levels by 10ng/ml after a year, and how did THAT correlate to positive or negative health outcomes? K2 also seems to play an important symbiotic relationship with D, and seems notably absent from these studies.
    - adgjlsfhk1 4mo ago
      if supplements don't absorb and therefore don't affect health, there's no reason to take them.
      - grep_name 4mo ago
        You missed the K2 part of his comment though. Both my mother and I have chronically tested incredibly low for vitmain D, both always taken supplements, both never had improvement. A couple years ago, my mom texted me saying she tried a D3+K2 supplement and for the first time in her life tested in range for vitamin D on her panel. I was skeptical but tried it, and have tested in normal range since.
- warmedcookie 4mo ago
  Yeah, I wish the article had brought Vitamin K2 into the mix since that seems trendy to pair with your D3 these days.
written-beyond 4mo ago
My life changed after I got tested for vit D and started talking supplements. I was severely deficient. I am now sufficient and everything changed for me.
- tweakimp 4mo ago
  What exactly changed?
- heisenbit 4mo ago
  In December by chance I put a pack of Vitamin D into my shopping basket. I did not think much, thought to take 1000IE but then decided that for the first week I take 3000 to catch up. Muscle pain went and control over eating improved. I did not expect any changes based on past experience with 1000 but this time I could not ignore it (age can play a role) and I stayed on 3000. Tests a month later showed I was just not deficient any-more. I continued on the regime and started having improvements in long running skin issues to the extent my dentist noticed. It may not be a miracle drug but one should not underestimate cumulative impact individual factors, age and lifestyle changes (less sun) that may change levels and demand.
  - regularfry 4mo ago
    I do think this is worth emphasising: the article only focuses on mortality. Not quality of life. Vitamin D makes me not feel like crap, it's cheap, and effectively zero risk. I'm not expecting it to make me live longer, I like that it makes me live better.
- legitster 4mo ago
  That doesn't undermine OP's point. Being deficient is unhealthy. But that doesn't mean an overabundance makes you healthier.
- wafflemaker 4mo ago
  I used to take 4k IU + K² and think that I'm covered, since 4K units was a lot. I landed on just above deficient when tested. My wife was on kind of same regime, but didn't follow it very strictly. She was deficient, but not extremely. It was quite surprising, because I got warned when buying 4k unit tabs that they were quite strong and pharmacy clerk suggested taking less.
nextos 4mo ago
Keep in mind vitamin D is really, among other things, an immune signaling molecule. So, we know the mechanism, and it's quite plausible that supplementation works. In other words, as an skeptic, I don't think it's just an epidemiological correlation.
mantas 4mo ago
It depends on one’s whereabouts and kind of exercise. Exercising in a gym or outside with all your skin covered won’t make much vitamin D.
smt88 4mo ago
Maybe this is true if you’re only considering white people. Brown people can spend a lot of time outdoors and still be deficient, especially if their ancestry is from much a much sunnier region or lifestyle than the one they’re currently living in.
- petesergeant 4mo ago
  Indeed: “Vitamin D deficiency in western dwelling South Asian populations: an unrecognised epidemic” … “27–60% of individuals, depending on season” https://pmc.ncbi.nlm.nih.gov/articles/PMC7663314/?utm_source=chatgpt.com https://pmc.ncbi.nlm.nih.gov/articles/PMC7663314/?utm_source...
- kevin_thibedeau 4mo ago
  It has never been established that darker people require the same amount of D as lighter. The supplement industry plays on these fearmongering to boost sales.
legitster 4mo ago
Ding ding ding. People who are drawing blood and trying to find some correlation between vitamin presence and health at this point are just practicing divination. The fact that it can be published in a scientific journal without any sort of RCT to back it up is palpably unscientific. The customers of these studies are the supplement companies looking for another product to sell.
kccqzy 4mo ago
I also suspect that the frequency of outdoor exercise matters even if the total duration of outdoor exercise remains the same. Subjectively, I feel much healthier when doing thirty minutes of outdoor exercise six times a week, than when doing one hour of outdoor exercise three times a week. But then of course, all the causal effects could have been caused by a different factor (say dopamine release) than vitamin D.
ChimpWithHat 4mo ago
Bingo. Obviously being deficient is bad, but the reason supplementation seems unimpressive is this is one of those proxies for healthy lifestyle. Kinda like how grip strength is correlated with longevity but banging out tons of hand gripper sets isn’t going to do much for you health.

I suspect that blood vitamin D is mainly a marker for how much outdoor exercise people are getting, and that it is the exercise rather than the D which is causal.

fragmede 4mo ago

But then why do we see improvements in people that get vitamin D + K2 supplements and not exercise?

amanaplanacanal 4mo ago
As the article mentions, we pretty much don't see improvements with supplementation.
- criddell 4mo ago
  From the article: > the balance of evidence tips pretty clearly in the direction that people with low-ish levels would be wise to supplement
- rzz3 4mo ago
  I don’t think there’s anything definitive. 400IU/day from one study is nothing if you’re deficient. 2000IU from another study is better, but even then we don’t seem to know much about absorption from these studies. For example, did it actually raise serum levels by 10ng/ml after a year, and how did THAT correlate to positive or negative health outcomes? K2 also seems to play an important symbiotic relationship with D, and seems notably absent from these studies.
  - adgjlsfhk1 4mo ago
    if supplements don't absorb and therefore don't affect health, there's no reason to take them.
    - grep_name 4mo ago
      You missed the K2 part of his comment though. Both my mother and I have chronically tested incredibly low for vitmain D, both always taken supplements, both never had improvement. A couple years ago, my mom texted me saying she tried a D3+K2 supplement and for the first time in her life tested in range for vitamin D on her panel. I was skeptical but tried it, and have tested in normal range since.
warmedcookie 4mo ago
Yeah, I wish the article had brought Vitamin K2 into the mix since that seems trendy to pair with your D3 these days.

written-beyond 4mo ago

My life changed after I got tested for vit D and started talking supplements. I was severely deficient. I am now sufficient and everything changed for me.

tweakimp 4mo ago
What exactly changed?
heisenbit 4mo ago
In December by chance I put a pack of Vitamin D into my shopping basket. I did not think much, thought to take 1000IE but then decided that for the first week I take 3000 to catch up. Muscle pain went and control over eating improved. I did not expect any changes based on past experience with 1000 but this time I could not ignore it (age can play a role) and I stayed on 3000. Tests a month later showed I was just not deficient any-more. I continued on the regime and started having improvements in long running skin issues to the extent my dentist noticed. It may not be a miracle drug but one should not underestimate cumulative impact individual factors, age and lifestyle changes (less sun) that may change levels and demand.
- regularfry 4mo ago
  I do think this is worth emphasising: the article only focuses on mortality. Not quality of life. Vitamin D makes me not feel like crap, it's cheap, and effectively zero risk. I'm not expecting it to make me live longer, I like that it makes me live better.
legitster 4mo ago
That doesn't undermine OP's point. Being deficient is unhealthy. But that doesn't mean an overabundance makes you healthier.
wafflemaker 4mo ago
I used to take 4k IU + K² and think that I'm covered, since 4K units was a lot. I landed on just above deficient when tested. My wife was on kind of same regime, but didn't follow it very strictly. She was deficient, but not extremely. It was quite surprising, because I got warned when buying 4k unit tabs that they were quite strong and pharmacy clerk suggested taking less.

nextos 4mo ago

Keep in mind vitamin D is really, among other things, an immune signaling molecule. So, we know the mechanism, and it's quite plausible that supplementation works. In other words, as an skeptic, I don't think it's just an epidemiological correlation.

mantas 4mo ago

It depends on one’s whereabouts and kind of exercise. Exercising in a gym or outside with all your skin covered won’t make much vitamin D.

smt88 4mo ago

Maybe this is true if you’re only considering white people. Brown people can spend a lot of time outdoors and still be deficient, especially if their ancestry is from much a much sunnier region or lifestyle than the one they’re currently living in.

petesergeant 4mo ago
Indeed: “Vitamin D deficiency in western dwelling South Asian populations: an unrecognised epidemic” … “27–60% of individuals, depending on season” https://pmc.ncbi.nlm.nih.gov/articles/PMC7663314/?utm_source=chatgpt.com https://pmc.ncbi.nlm.nih.gov/articles/PMC7663314/?utm_source...
kevin_thibedeau 4mo ago
It has never been established that darker people require the same amount of D as lighter. The supplement industry plays on these fearmongering to boost sales.

legitster 4mo ago

Ding ding ding. People who are drawing blood and trying to find some correlation between vitamin presence and health at this point are just practicing divination. The fact that it can be published in a scientific journal without any sort of RCT to back it up is palpably unscientific. The customers of these studies are the supplement companies looking for another product to sell.

kccqzy 4mo ago

I also suspect that the frequency of outdoor exercise matters even if the total duration of outdoor exercise remains the same. Subjectively, I feel much healthier when doing thirty minutes of outdoor exercise six times a week, than when doing one hour of outdoor exercise three times a week. But then of course, all the causal effects could have been caused by a different factor (say dopamine release) than vitamin D.

ChimpWithHat 4mo ago

Bingo. Obviously being deficient is bad, but the reason supplementation seems unimpressive is this is one of those proxies for healthy lifestyle. Kinda like how grip strength is correlated with longevity but banging out tons of hand gripper sets isn’t going to do much for you health.