When I had my first baby, I knew the baby needs to be outside as mush as possible to get enough sun light to produce much needed Vitamin D. According to Mayo clinic:
"While breast milk is the best source of nutrients for babies, it likely won't provide enough vitamin D. Your baby needs vitamin D to absorb calcium and phosphorus. Too little vitamin D can cause rickets, a softening and weakening of bones."
What about the grown ups and Vitamin D?
Watching for years ongoing fight against dairy products and sun exposure, I kept thinking to myself that this generation is going to have problems with Vit. D. It is when I started working closely with women and men treating their skin, I got the proof that my worries are valid.
First I noticed that women concerned with extra weight, especially fluid retention, found out during their physical or having their blood checked, that they have low numbers of Vitamin D.
Also women with sensitive and/or reactive skin with signs of light Rosacea, inflammation and excessive dryness had low levels of Vitamin D. as soon as they started supplementing Vit. D, skin would improve quickly. Then we could precede with micro-needling, light peels and other treatments that were off the table before. But how could it be happening in Colorado with mostly great weather, outdoor lifestyle and an abundance of Sunny days?
I started researching this topic and found a wonderful article.
"The "sunshine" vitamin is a hot topic. You may have recently found out that you are deficient or know someone who is. It's shocking for most people when they have never had a problem before and believe nothing has changed to make it a problem now. The truth is that a lot has changed, and vitamin D deficiency and insufficiency is now a global public health problem affecting an estimated 1 billion people worldwide."
Please read this article https://www.medicinenet.com/vitamin_d_deficiency/article.htm
I cannot imagine explaining it better than this article does.
I found medicinenet.com to be a very intelligent source of popular health related info.