Megadosing B12 (if your diet isn't already sufficient in it, which is common amongst certain vegan diets) is still a good idea, no? I recognize this might be the only exception.
Personally, I dose 4000-5000 IU D3+K2 in the darker seasons and that has been working well for me.
Vitamin B12 is water-soluble and therefore should not cause accumulation in healthy people.
Calcium, magnesium, sodium, and potassium in balanced amounts along with K and D maximize bone health. Alkali metals supplementation alone is rarely a good idea because of the often common transports and osmotic competitions.
In general, a multivitamin, b complex, and omega 3 in the form of canned fresh sardines or anchovies (fish oil capsules are typically low in actual 3 and high in 6) is probably enough for most people.
5-10 mg/day of extra zinc during the annual cold season is fine too.
Don't supplement with E without a specific medical need.
My beginning D3 levels were 39 ng/ml, so just under the ideal range of 40-60, and not really deficient. I have not tested recently, though I believe my numbers would be higher now. I also try to get at least 30 minutes of sun exposure over most of my body 3-4 times per week. Fortunately I live where I can get good sun exposure year-round. Point is, test your serum D3 level and do whatever you need to get into the desired range, and don't take more than that level of supplementation. I do believe that sun exposure is a better choice than supplements, if practicable.
I'm entirely untrained, but my amateur evaluation of the situation leads me to take 50,000 IU orally once each week or two. I imagine that twice that amount would be fine, too.
That's not really science.
Given it's your body, the most valuable thing you have, perhaps a more fact-based approach is warranted?
For instance, it may be monkeying around with blood flow to the kidneys somehow.
"Among patients with diabetic nephropathy, high doses of B vitamins compared with placebo resulted in a greater decrease in GFR and an increase in vascular events."
https://jamanetwork.com/journals/jama/fullarticle/185758
House AA, Eliasziw M, Cattran DC, et al. Effect of B-Vitamin Therapy on Progression of Diabetic Nephropathy: A Randomized Controlled Trial. JAMA. 2010;303(16):1603–1609. doi:10.1001/jama.2010.490
So, it's probably fine, but honestly nobody really knows.
... if you're doing heroic doses of something you can't pee out then it's a bit worse
For example, elevated B12 levels are associated with increased lung cancer risk in a dose-response fashion: https://pubmed.ncbi.nlm.nih.gov/30499135/
The only time megadosing B12 is a good idea is if you have confirmed low levels via a blood test and need to quickly raise your levels to the normal range.
Don’t assume you can guess your B12 status by reading random articles on the Internet. Low B12 has become a favorite hypothesis among the alternate medicine crowd, so online information about B12 supplementation has become corrupted with pseudoscience.
I’ll admit that I fell for the idea that B12 deficiency was rampant due to modern diets. Then I got a blood test and discovered that my B12 levels were toward the upper end of the reference range already.
On the bright side, B12 absorption is very nonlinear. A megadose might only cause slightly more absorption than what you find in a regular multivitamin. Most of the megadose is simply not absorbed.
That being said most people who aren't severely restricting the types of food they eat, and eating healthy food, are unlikely to have significant malnutrition.
The lung cancer thing I remember was specifically smokers, so its not straightforward.
There are some data suggesting that inadequate supply of this or that nutrient reduces certain aging mechanisms and leads to longer lifespans in a laboratory setting. However, outside of a laboratory setting these nutrient deficiencies can affect the body's ability to fight infections and heal injuries, which on average cancels out any benefits.
More generally, trying to increase lifespan by adjusting the diet seems to me like trying to fix a car by playing with the buttons and knobs on the dashboard. You might obtain a small improvement, but you're not really going to get anywhere unless you open the hood.
This happened to me after I inadvertently megadosed by consuming a knock-off Berocca drink containing something like 10x RDI.
That was over 10 years ago. I have not had a gout attack since.
Edited: Risk is actually for Vit B3 (Niacin). The drink I had contained massive amounts of B12, B3 and others.
https://www.mayoclinic.org/drugs-supplements-niacin/art-2036...
Here's a breakdown of the DV for some of the vitamins for a full serving:
B1 = 33x (yes, 3333%)
B2 = 30x
B6 = 40x
B12= 83x
Is that (and the amounts mentioned) based on science, or just what some gymnast dude said?
The technical term is broscience
https://www.vitacost.com/natural-factors-whole-earth-sea-bon...
They liquify plants and then ferment them in some proprietary process that they don't go into detail about (I wouldn't be surprised if they use some GMO bacteria that goes against the non-GMO advertising, since many commercial vitamins are produced by GMO bacteria). I just use two pills a day (what the chart shows data for, most vitamins from 1/3 to 2/3 of recommended daily amount). Eating a healthy diet, there should be no need for 100% or more of nutrients in a supplement, but it is frustratingly difficult to find reasonably dosed multivitamins.