Article from Weston A Price - https://www.westonaprice.org/health-topics/vitamin-a-mazing/#gsc.tab=0

VITAMIN A FOR EVERYTHING

Why do we say that vitamin A is needed for almost every function in the human body? We first think of it for vision and eye health. The true form of vitamin A is called retinol as its name corresponds to its importance for the retina of the eye. However, apart from vision, we need vitamin A for every surface of our body including our skin, eyes and gut.

Vitamin A keeps us from getting sick; it keeps our immune system from overreacting; it is necessary for growth and reproduction. We need vitamin A for building bones and teeth, and for the actions of our hormones. These are major roles, ones we’ve known about for a very long time, but there are others.

How does vitamin A do so much? It regu­lates the action of over five hundred genes in the body, which makes it a major regulator of all of our cells and how they function. Starting at conception vitamin A orchestrates the proper division and differentiation of every cell in the body. When cells differentiate properly, they are doing what they are supposed to do. You might say that vitamin A keeps our cells “behaving.”

How does vitamin A influence our genes? It works through something called nuclear hor­mone receptors—more precisely, retinoic acid receptors and retinoid X receptors. These recep­tors travel in the nucleus of the cell, binding and forming combinations with each other and with other compounds, like vitamin D and thyroid hormones. These receptors act to influence the action of our genes, which then influence which proteins are made, and ultimately, our whole metabolism.

By the way, every time we use a vitamin D molecule in the body, we use a vitamin A molecule also. That is why we must always think of these two nutrients together.

Without understanding anything about vitamins, traditional people always knew that special foods, ones that we now know are rich in vitamin A, were important to their health. Before the 5th century BC, vitamin A-containing foods such as liver were consumed and applied to the eyes and skin for healing purposes. Even Hippocrates documented this practice.

Scientists McCallum, David and Mendel discovered and named vitamin A in 1913. Dr. Price began his work less than two decades after this discovery, so he was acutely aware of the importance of vitamin A. However, not long after Dr. Price’s Day, interest in vitamin A waned. Fortunately, there has been a resurgence of interest in vitamin A, with exciting discover­ies in the fields of auto-immune disease, neurol­ogy, energy metabolism, cancer, stem cells and epigenetics.

According to Norwegian researchers Blom­hoff and Drevon, authors of an important text­book on vitamin A, “After a period of rather low interest in the fat-soluble vitamins (we know as vitamin A, D, E, and K) we are now in the midst of a new wave of research on these vitamins with a large number of reports in influential national journals.. Suboptimal status has been linked to several diseases.