Hello everyone on the internet! It’s vitamin A day! Hooray! We are going to be chatting about all things vitamin A.
This post is to help kick off a new thing I’m calling “The Micronutrient Series.” In case you didn’t know, micronutrients are components of the diet that can’t be made by the human body and are therefore required in the diet, usually in small amounts; they include vitamins and minerals. I plan to chronicle all the micronutrients from vitamin A-zinc in this series.
Each vitamin or mineral will have a post like this one, where I explain what the micronutrient does, how it is absorbed and used in the body, food sources of the micronutrient, and what too much of the vitamin may do to you.
Please take note that this series will be rolling out slowly, as there are many micronutrients! But I hope you’ll stick around for the ride. If you have questions about RDA and DRIs, please see this post. Otherwise, let’s chat vitamin A!
‘Vitamin A’ is the name of not one, but rather, a group of fat-soluble retinoids. It includes retinol, retinal, and retinyl esters.
There are two forms available in the human diet: preformed vitamin A and provitamin A (often called carotenoids). Both must be metabolized into retinal and retinoic acid for use in the human body.
Preformed vitamin A is found primarily in animal food products, such as meat, fish, and diary.
Provitamin A is found mostly in plant foods. Beta-carotene is the most important provitamin A in the human diet, and is prevalent in foods such as carrots and sweet potatoes.
What Vitamin A Does in Your Body:
Vitamin A does a lot of things in your body. Often associated with good vision, vitamin A is indeed critical to make rhodopsin, a protein that absorbs light in retinal receptors in your eye, thereby ensuring proper vision.
But vitamin A does more than help you see. It also plays an important role in cell growth and differentiation, and is critical for normal formation and maintenance of the lungs and kidneys, among other organs. Vitamin A also plays a role in gene expression and a large body of research also supports the role of vitamin A in regulation of genes involved in immunity.
Vitamin A also plays an important role in reproduction and human development. In males, vitamin A participates in sperm development, and in women, vitamin A promotes healthy fetal growth and development. Vitamin A is transferred from the mother to fetus to ensure proper development of the nervous system, lungs, kidneys, heart, skeleton, eyes, and ears.
Some human epi studies have shown that adequate intake of vitamin A from food is associated with lower risks of certain cancers; however, studies have also shown that overconsumption of vitamin A from supplement specifically can be harmful (more on this in the toxicity section).…