It's very hard to take toxic amounts of vitamin D:
> "Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity. This level is many times higher than the U.S. Recommended Dietary Allowance (RDA) for most adults of 600 IU of vitamin D a day.
Not saying it's impossible, but that's the equivalent of buying the top result on amazon (https://www.amazon.com/Nature-Made-Vitamin-Strength-Softgels...) and taking 12 polls a day for several months. It's not actually impossible to get to toxic levels... but that's a serious commitment.
As far as I'm aware Vit D toxicity has been observed in much higher doses than 4000 IU/day. Do you have a quote for the 4000 IU/day figure?
The skin produces up to 10,000 IU/day after exposure to UV light⁰. The same study I'm quoting shows toxicity levels at over 20000 IU/day for adults. One person in the study has taken 156,000–2,604,000 IU/day for 2 years!
The production in the body is self-regulating though, so you can't overdose from sun exposure. Supplements can bring you over the limit, because you absorb what you're given.
You are arguing a point I didn't make. My point was to his statement that 4000 IUs/day were toxic (without stating any basis for that number), while the study I quote claims that the body produces up to 10000 IUs/day – so clearly the toxicity limit is not an unqualified 4000 IUs/day. Perhaps in some people toxicity appears at lower doses while in other people at higher doses.
I'm not really disputing the 4k not being toxic. Just the way I understand it, even though you can produce up to 10kUI through the skin should have no relation to the toxicity level being below or above 10kUI.
> "Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity. This level is many times higher than the U.S. Recommended Dietary Allowance (RDA) for most adults of 600 IU of vitamin D a day.
(https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...)
Not saying it's impossible, but that's the equivalent of buying the top result on amazon (https://www.amazon.com/Nature-Made-Vitamin-Strength-Softgels...) and taking 12 polls a day for several months. It's not actually impossible to get to toxic levels... but that's a serious commitment.