Great article. There is a direct link between vitamin-D deficiency and the severity of colds, flu and (of course) COVID.

Wikipedia currently classifies Vitamin D as a "secosteroid."

They keep changing the classification.

It is essentially a hormone that seems to regulate bone creation, the immune system, and other parts of our health.

From an evolutionary perspective, vitamin D is quite important. This chemical appeared before invertebrate. All animals that have bones have vitamin D.

I wish that medical community provided better information about sunlight and vitamin D production.

Looking up different articles. It appears that our skin produces 7-dehydrocholesterol . UVB radiation turns 7-dehydrocholesterol into vitamin D3. A healthy liver turns vitamin D3 into vitamin D2.

It is the UVB radiation that transforms 7-dehydrocholesterol.

This spectrum also causes skin cancer.

The earth's atmosphere filters out UVB. Most windows filter UVB radiation.

Since the atmosphere filters UVB radition, the best time to get sunlight is at noon when the sun is directly overhead. This rule may not apply year round.

Again the controversy is that UVB causes skin cancer and produces vitamin D.

My understanding is that people in Northern climates develop vitamin D defiencies during the Winter because the UVB radiation is blocked during the winter.

Again, I wish the medical community provided better information on the best time to produce vitamin D.

Another controversy. It appears that the free fructose found in invert sugars like High Fructose Corn Syrup will destroy vitamin D in the liver. HFCS and invert sugar is found in a large number of foods these days as it makes things taste sweet.

!WINEX