He simply doesn't understand Vitamin D at all. He is talking BS.
There is no mystery about the production of vitamin D3 in the skin or the way vitamin D toxicity from sunlight is prevented by the self regulating process of into supra sterols.
uvguide explains the process
Extra sun on vitamin D3 that remains unabsorbed on or near the surface of the skin DOES NOT get converted to D2 instead it gets converted into three new substances: two suprasterols and 5,6 trans-vitamin D.
Similarly he is wrong about the toxicity of both D3 and D2 there are more examples of D2 toxicity than D3 so the safest form is D3.
Vitamin D2 Is Much Less Effective than Vitamin D3 in Humans
The case against ergocalciferol (vitamin D2) as a vitamin supplement
The problem with calcium is related to other factors.
First and most important is the use of calcium supplements while raising Vitamin D status. Most people are vitamin D deficient at present.
Correcting vitamin D insufficiency increases the amount of calcium they can absorb from food/water/supplements.
Therefore as vitamin d status moves from deficiency to sufficiency the need for extra supplemental calcium reduces because a higher percentage of the calcium from diet and water is being absorbed.
Calcium tenses muscle fibres and excites brain neurones.
Magnesium relaxes muscle fibres and calms brain neurones.
Therefore when people have too much calcium and insufficient magnesium they tend to get muscle cramps and feel tense and edgy.
This is NOT the fault of vitamin D.
It's because that person is MAGNESIUM DEFICIENT
Because as many people are magnesium deficient as vitamin D deficient both need to be corrected. Vit d controls over 2000 different enzyme actions Magnesium around 350 actions so get these two wrong and the number of different permutations of deficiency scenarios is huge.
Because magnesium acts as a natural calcium channel blocker it counterbalances the role of calcium. Ideally you need around
5 to 10 milligrams per day per kilo of ideal body weight or 2.5 to 4.5 milligrams per day per pound of ideal body weight.
I haven't finished listening to the talk (the vitamin D section is at 1HR 12MINS by the way) but will do so later when in need of a good laugh. I don't think I've ever heard anyone talk as much unscientific nonsense about vitamin D as Dr. Jameth Sheridan.
His understandings of vitamin D2 and D3 has no basis in modern science.
Because D2 is the plant form many humans are completely unable recognize D2 or convert D2 into D3, they can take any amount of D2 (200000IU/daily) to no effect whatsoever either harmful or good.
All of us who can convert D2 into D3 do so less effectively than using D3 initially.
So for most people 6000iu D2 = 2000iu D3.
At the levels most people require to keep a natural 25(OH)D around 60ng/ml D2 is less effective than D3.
I should perhaps have said a word about sunshine. You should get
tested to check if using sun is working for you where you live.
First vitamin D is made from the action of UVB on cholesterol in skin.
NO UVB = NO VITAMIN D
The amount of local ozone pollution from traffic, air travel, factories is such that at some times of the year and in some towns/cities insufficient UVB reaches the ground.
NO CHOLESTEROL = NO VITAMIN D
People taking statins, people on low cholesterol diets, older people with thinner skin ALL will have a lower potential for making D3 from sunlight.
Skin colour will also affect the amount made, that is why the skin least exposed, least tanned generates more vitamin d than hands/face that are regularly exposed.
UVA as detailed in the UV guide processes the newly made D3 into products the body doesn't use so if you use sunscreen AFTER making your vitamin D AND you stay in the sun it's possible that extra UVA only exposure could degrade the newly made D3.
Vitamin D is fat soluble.
Sweat contains some fat.
Indulging in vigorous exercise while sunbathing such that you sweat inevitably brings D3 to the skin surface. If you shower, swim towel down you remove the D3. Marathon runners, Cyclists and athletes all generally have low vitamin D status even though they spend lots of time in the sun practicing their sport.
There are many people who get regular sun exposure but who still have low vitamin D status. It is far safer to take a basic amount of D3 such as 5000iu AND then rely on your body's ability to self regulate D3 production to fill the stored reserve stores with D3. People with higher vit d levels generate less than those with low status given same UVB exposure.