Vitamin D supplementation for vitamin D deficiency that is quite common is not controversial at all.

If you mean taking more D than is needed, your are correct.

You can measure the D vitamin levels from blood serum.

  <    30  nmol/L is vitamin D deficiency

  30 - 50  nmol/L is considered inadequate

  50 - 125 nmol/L is adequate

  >    150 nmol/L evidence of potential adverse effects 

Adequate level has increased over the years.

but shouldn't you always complement vitamin d intake with vitamin k? If I recall correctly (I am not sure!) then vitamin d without vitamin k can be harmful.

Vitamin K is found in vegetables, so you don't need to supplement it. I think the worry is that too much Vitamin D contributes to buildup in arteries over the long term, and K helps to clean it.

I'll bite: https://en.wikipedia.org/wiki/Vitamin_K#Food_sources

>Vitamin K is found in vegetables

"Vegetables" is a category that's about as useful in this context as "food".

Greens.

I think with vitamin D supplementation you also need to consider vitamin A intake.

Spinach and eggs every morning more than covers you there

Greens and broccoli are the only vegetables I believe in. Everything else is guinea pig food.

Vitamin D is the only supplement that the NHS recommends for the general population, particularly over winter. I’m happy to take it.

Can you elaborate? I've never heard anything about that before.

Your body can handle massive amounts of vitamin C and D, so its a bit surprising to hear that supplementing the (generally) small amount you'd find in a vit D pill could be harmful.

While it is basically impossible to overdose on Vitamin C, you can overdose on Vitamin D. It is fat-soluble, thus overdosing has a cumulative and delayed effect.

https://en.wikipedia.org/wiki/Hypervitaminosis_D

However, that does not mean that vitamin D supplements are suspect in principle, just that before starting on a course of supplements, it might make sense to have your Vitamin D levels checked and the right dosage determined.

From your page: > The recommended dietary allowance is 15 µg/d (600 IU per day; 800 IU for those over 70 years). Overdose has been observed at 1,925 µg/d (77,000 IU per day).

So it seems you could even take 10x the recommendation and be fine. The risk of a reasonable supplement pushing you into overdose territory seems negligible.

Yes, indeed!

http://www.mayoclinicproceedings.org/article/S0025-6196(15)0...

"The evidence is clear that vitamin D toxicity is one of the rarest medical conditions and is typically due to intentional or inadvertent intake of extremely high doses of vitamin D (usually in the range of >50,000-100,000 IU/d for months to years)".

The significant advantages of D3 supplementation for sun-starved people are evident in the literature.

And according to EPIC series epidemiology somewhere between 2000 and 3000 IU seems best at total mortality. It is a very flat J curve though.

As far as I've heard 10,000 IU is regarded as almost definitely non-toxic, and toxicity seems to have been noticed around 40,000 IU per day.

However, in the summer you may want to drop that below 5,000 or even stop supplementing completely, depending how much you're in the sun.

Vitamin K2 also seems to be necessary in combination with D3. But it's not clear to me if 100 mcg MK-7 is enough or if you need to supplement Mk-4 more often or eat more MK-4 foods (the latter is probably preferable).

The largest-dose individual, non-prescription vitamin D supplement pill I have ever seen is 5000 IU, so you'd have to take 10 of those every day, for months, to develop a toxicity symptom. At that point, the per-pill cost of the supplement and the sheer number of pills combine to discourage overdose.

If you have a confirmed deficiency, a doctor can prescribe a limited course of higher-dose pills to get your serum levels back up quickly.

I take cholecalciferol (D3) and menatetrenone (K2-MK4) daily, along with a multivitamin that was essentially a gratis 2.7-year supply, thanks to a fortuitous coupon + sale price interaction, so it isn't actually just making my pee more expensive. I'd feel wasteful throwing it away after someone paid me to take it home, and it'd be great if it activated a placebo effect.

Also, I can't bring myself to like natto.

BTW, rumor has it the RDA was miscalculated and should be about twice as high.

https://examine.com/nutrition/should-1000-iu-be-the-new-rda-...