8/23/2026 at 5:56:09 PM
Study was in an elderly cohort with cognitive impairment. This is a cohort more likely to have nutrition and diet problems and spend all of their time indoors. I haven’t found the full study but the results look marginal for a narrow group.Then there’s this important note in the highlights:
> Higher daily Vitamin D intake may impact cognition in persons with sleep disturbance and MCI.
More is not better with Vitamin D. Correcting deficiencies is good but the mega dosing trend is not.
by Aurornis
8/23/2026 at 7:34:46 PM
Don't go overboard, but you have quite a bit of margin for error. I am finding one claim that the upper maximum daily dose for Vitamin D is 4000 IU. A Costco daily multivitamin is 400 IU (most adults are recommended at 600 IU).If you start supplementing with a traditional, OTC Vitamin D option, likely very low risk of complications.
by 3eb7988a1663
8/23/2026 at 5:59:40 PM
I'd like to add that correcting deficiencies implies seeing a physician to get your dosage right. This is necessary both for Vitamin D and Melatonin.If you're not a sedentary geriatric with MCI this study is probably not for you.
by phoronixrly
8/23/2026 at 6:01:02 PM
Sadly, many people in northern areas who are otherwise healthy are vitamin D deficient. It can be a side effect of trying to protect from skin cancer.by zulux
8/23/2026 at 6:10:15 PM
I am not arguing against that. I argue that correcting this deficiency is not in the competence of people who are not medical professionals no matter how many articles they've read on the front page of HN about vit. D.by phoronixrly
8/23/2026 at 6:11:28 PM
You can very much overdose on Vit D. I suspect your risk tolerance is different than mine.by zulux
8/23/2026 at 10:11:28 PM
You need to be quite irresponsible and blindly take large doses for extended periods of time to achieve this though - and there's a significant margin between what's considered a "too high" level and what's actually known to be toxic. Do keep your levels in check (you don't need to see a doctor to do that), but there's no need to be overly scared.by seba_dos1
8/23/2026 at 8:56:31 PM
You can very much overdose with melatonin as well, leading to your sleep schedule getting worse and worse the larger the dose. Ask me how I know before assuming my risk tolerance.by phoronixrly
8/23/2026 at 6:13:26 PM
You are speaking nonsense and lies, considering anyone can get themselves tested. Visiting a doctor is not needed for it.Doctors are in fact notoriously bad when it comes to vitamin D. None of the docs that I have ever visited eagerly tested my level. I always had to beg for a test. Moreover, none of them ever helped me optimize my level. It is tragically dangerous and harmful to rely on them for it.
by OutOfHere
8/23/2026 at 7:38:04 PM
> Doctors are in fact notoriously bad when it comes to vitamin D.Most doctors know nothing about the endocrine system, at all. I self taught myself through "Endocrinology: Adult and Pediatric" and I probably know more than 99% of general practitioners out there. Heck, most doctors are likely unaware of the endocrinological functions of D3.
On Endocrinology: Adult and Pediatric, I consider it a must read for anyone btw
by rfgplk
8/23/2026 at 6:25:44 PM
What conflict of interest would that be? I'm getting paid by big doctor to tell adtech devs with unchecked egos to go ask someone who has actually dedicated 10+ years of their life to study and practice medicine?by phoronixrly
8/24/2026 at 1:14:10 AM
Don't kid yourself. The formal requirement remains at 600 IU which is murderous for anyone who succumbs to obeying it. This formalism proves the malfeasance of the medical profession.by OutOfHere
8/23/2026 at 6:03:34 PM
This guy will get you killed. It is reasonable to maintain a blood level of about 45 ng/mL. This often requires 5000 IU/day, perhaps less in seniors with weaker kidneys, or those with heavy sun exposure which is dangerous for other reasons. You don't need to see a doctor for this, but you do need to get the test done every year or two. Personally I prefer not involving a doctor for any of it.Nobody disputes that excessive vitamin D is not good, but maintaining a blood level below 45 ng/ml also is not good. Covid studies had ascertained that a level of at least 50 ng/ml was optimal.
by OutOfHere
8/23/2026 at 7:40:29 PM
> 5000 IU/dayIronically these "IU/day" estimates are bogus. Direct ~noon sunlight at the equator for fair skinned individuals produces (full body exposure) 15-50k IU/hour of D3 equivalent, depending on the estimate. You clearly don't see people dropping dead after two hours in the sun.
GPT response For a fair-skinned adult, nude or essentially whole-body exposed, at solar noon near the equator under a clear sky, a reasonable order-of-magnitude estimate is:
Exposure Approx. D3-equivalent produced ~3 min ~2,500–6,000 IU ~5 min ~4,000–10,000 IU ~10 min ~8,000–20,000 IU ~10–15 min / ~1 MED ~10,000–25,000 IU >20–30 min does not keep increasing linearly
The best-known experimental anchor is that roughly one full-body minimal erythema dose (1 MED)—enough UV to cause faint redness later—is associated with a vitamin-D effect comparable to ingesting about 10,000–25,000 IU (250–625 µg) of vitamin D3. Reviews note that this estimate has also received support from outdoor solar-exposure studies, although the original experiments used artificial UV sources. https://pmc.ncbi.nlm.nih.gov/articles/PMC3257661/ study
by rfgplk
8/23/2026 at 6:18:57 PM
> This guy will get you killedYeah, no. Advising people to correct Vitamin D deficiencies but to avoid overdosing is correct.
I quoted the study. The study agrees that excessive Vitamin D consumption is not good.
by Aurornis
8/24/2026 at 1:08:56 AM
An excess of anything is not good. The point is that insufficient supplementation leaves most people far below the optimal blood level of vitamin D, typically even in a hazard zone, and doctors do absolutely nothing to address the situation. As the definitive case in point, they maintain the formal requirement at 600 IU which shows their intent to kill everyone who isn't better informed.by OutOfHere