Every vitamin has a letter, but only one of them earned its letter first. Vitamin A was the very first vitamin ever isolated from food and formally named, discovered years before B, C, D, E, or K had been identified at all, which is the entire reason it sits at the front of the alphabet. The story behind that discovery, and a distinction inside vitamin A itself that most labels never explain, are both worth understanding properly rather than in the shorthand most wellness content settles for.
This is the full picture: what vitamin A actually is, how it was found, why it comes in two genuinely different forms that behave nothing alike once inside the body, and how that difference shapes two very different formulas in our own lineup.
What Vitamin A Actually Is
According to the NIH Office of Dietary Supplements, "vitamin A" is not one single molecule. It is the name for a group of fat-soluble compounds called retinoids, chiefly retinol, together with a separate family of plant pigments called provitamin A carotenoids, the best known of which is beta-carotene. Both groups are commonly labelled "vitamin A," but as this article gets into, they are not interchangeable, and the difference between them is the whole reason this vitamin needs its own explainer rather than a single-line dictionary definition.
The Discovery Story: How a "Fat-Soluble Factor" Became the First Vitamin
The story starts not with vitamins at all, but with cattle. In the early 1900s, researchers at the University of Wisconsin–Madison, led by biochemist Elmer McCollum, were investigating why cows fed different grains thrived or sickened in ways plain calorie counts couldn't explain. In 1910, McCollum shifted the work from cattle to lab rats, a faster and cheaper way to test diets systematically, and in 1912 he was joined by Marguerite Davis, a biochemistry researcher who spent years running the rat colony feeding trials by hand.
Their key finding: rats fed a purified diet built around lard or olive oil as the only fat source stopped growing and their eyes became inflamed, while rats fed the same diet with butterfat or egg yolk swapped in kept growing normally. Something in those animal fats, absent from the plant oils, was essential for growth, and it dissolved in fat rather than water. McCollum and Davis published the finding in the summer of 1913, in the same issue of the Journal of Biological Chemistry as a closely related, independently-run study from Thomas Osborne and Lafayette Mendel at Yale. Between them, this is generally regarded as the first time a specific, isolable dietary compound had been experimentally shown to prevent a deficiency disease, which is why vitamin A, rather than any other nutrient, is usually credited as the first vitamin identified by science.
The letter came a few years later, not immediately. McCollum initially called his discovery simply "fat-soluble factor A." In 1916, working with fellow researcher Cornelia Kennedy, he formalized an alphabetical naming system to distinguish it from a second, water-soluble growth factor his lab had also identified, which became "factor B." The simplified "vitamin" terminology itself, dropping "fat-soluble" and "water-soluble" in favor of a clean letter system, was proposed a few years after that, popularized around 1920 by the biochemist Jack Drummond. By the time the dust settled, the nutrient McCollum and Davis had isolated in 1913 carried the name vitamin A, first in the alphabet because it was first in the lab.
Two Different Forms, One Name
This is the part that matters most for anyone actually taking a supplement, and it's also the part most product labels gloss over: "vitamin A" on an ingredients panel can mean one of two genuinely different things.
Preformed vitamin A is retinol and its close relatives, retinyl esters like retinyl acetate and retinyl palmitate. It occurs naturally in animal-sourced foods, liver, dairy, egg yolk, and it's called "preformed" because the body can use it essentially as-is, with minimal conversion required. Supplement labels that list "retinol" or "retinyl acetate" are using this form.
Provitamin A carotenoids are a different category entirely: plant pigments, the best known being beta-carotene, found in carrots, sweet potatoes, and leafy greens, and responsible for a lot of the orange and deep-green color in produce. These aren't active vitamin A on their own. The body converts them into usable retinol only as needed, through an enzyme-controlled process that scales up or down depending on how much active vitamin A is already available.
That single difference, direct use versus regulated conversion, is the spine of everything else worth knowing about vitamin A, including why two different Vitameenat formulas make two different, equally defensible choices about which form to use.
Why the Form Matters for Safety
Preformed vitamin A is absorbed efficiently and stored, mostly in the liver, for later use. That storage capacity is exactly what makes it different from a water-soluble vitamin like C or the B-complex, which the body simply excretes when there's more than it needs. Taken in excess over time, preformed vitamin A can build up to levels associated with toxicity, and the NIH Office of Dietary Supplements sets a tolerable upper intake level of 3,000mcg per day for adults, above which the risk of adverse effects, including liver strain and, in pregnancy, birth defects, rises.
There's a subtler concern worth being honest about too. The same NIH fact sheet notes that observational studies have suggested an association between high intakes of preformed vitamin A, generally more than 1,500mcg daily, and both reduced bone mineral density and increased fracture risk. It's a genuinely documented association, not a fringe claim, but it also isn't a settled one: the NIH is explicit that results across these studies have been mixed, and that no safe threshold specific to bone health has been established, which is why it wasn't used as the basis for the official upper limit. The honest summary is that it's a real reason for caution around high-dose preformed vitamin A specifically, not a reason for alarm at ordinary intakes.
Provitamin A carotenoids don't carry this same risk. Because the conversion from beta-carotene into active vitamin A is regulated by the body itself, rather than absorbed wholesale the way retinol is, there's no equivalent accumulation pathway and no comparable upper limit for vitamin A toxicity from beta-carotene alone. It's a real, structural safety difference between the two forms, not a marketing distinction, and it's precisely why a thoughtfully formulated product has a choice to make: dose preformed vitamin A conservatively, or lean on the provitamin A route instead. Both are legitimate answers, and which one makes sense depends on what else the formula is trying to do, which is exactly the comparison below.
What Vitamin A Actually Does in the Body
Once it's active in the body, regardless of which form it started as, vitamin A has a genuinely broad job description.
Vision. This is vitamin A's best-known role, and for good reason: retinol is a direct structural component of rhodopsin, the light-sensing pigment in the retina that makes vision in low light possible. It's the reason severe vitamin A deficiency has historically been a leading cause of preventable blindness in parts of the world where it's common.
Immune function. Vitamin A supports the normal development and function of immune cells, and plays a role in maintaining the mucosal barriers, the lining of the gut, lungs, and other tissues, that form the body's first line of defense against pathogens.
Skin and epithelial health. Vitamin A is required for the normal formation and maintenance of skin and other epithelial tissue, the kind of structural, everyday maintenance work that shows up as skin doing its normal job rather than anything dramatic. We've gone deep into this specific angle, and specifically why Inner Beauty is built around beta-carotene rather than retinol for it, in our dedicated guide to provitamin A and skin cell renewal, so we won't repeat that ground here.
Cell growth and differentiation. Underneath most of vitamin A's other roles is a more fundamental one: it helps direct how immature cells mature into the specialized cells a given tissue actually needs, a process called cell differentiation. This is the mechanism behind vitamin A's roles in vision, skin, and immune function alike, rather than a separate function of its own.
Two Different Jobs Across the Vitameenat Lineup
Because the two forms of vitamin A carry genuinely different safety profiles, it's not surprising that our own formulas make two different choices, and it's worth being straightforward about why, rather than implying one is simply the better one.
Daily Essentials: Preformed Vitamin A, Deliberately Restrained
Daily Essentials delivers 400mcg of vitamin A, 50% of the Reference Intake, as retinyl acetate, a preformed form, inside its MultiVitamin component. Fifty percent is a deliberate choice, not a shortfall. As a broad, everyday multivitamin that already includes several other fat-soluble nutrients in its formulation, holding preformed vitamin A at half the reference intake delivers a genuinely useful, direct contribution without pushing anywhere near the intake levels where the bone-health question above becomes relevant, let alone the official upper limit. It's a demonstration of dose restraint with a fat-soluble, storable vitamin, done on purpose.
Inner Beauty: The Provitamin A Route, for a Different Goal
Inner Beauty takes a different path entirely. It delivers 10mg of Betatene, a beta-carotene extract, as part of its Collagen component, alongside vitamin C, vitamin E, and zinc. Betatene is a provitamin A precursor, not preformed vitamin A, which means Inner Beauty can provide a meaningful vitamin A contribution to its skin-focused formula without the accumulation question that comes with dosing retinol directly, since the body converts only what it actually needs. For the specific mechanism behind why that matters for skin cell renewal, and why beta-carotene rather than retinol fits Inner Beauty's formulation goals, our guide to provitamin A and skin cell renewal covers it in full.
Neither approach is simply better than the other. Daily Essentials is asking preformed vitamin A to do a broad, foundational job at a conservative dose; Inner Beauty is asking the provitamin A route to support a specific, skin-focused formula at a more generous one, without inheriting the retinol accumulation question at all. They're two reasonable, honestly different answers to the same underlying design question, chosen for two different formulas with two different jobs to do. For where vitamin A fits alongside the rest of what a daily routine actually needs, our guide to the daily essential supplements worth taking is the wider picture.
Quick Facts: Vitamin A at a Glance
| Fact | Detail |
|---|---|
| Classification | A group of fat-soluble retinoids (preformed) and provitamin A carotenoids (precursor) |
| First isolated | Elmer McCollum and Marguerite Davis, University of Wisconsin–Madison, published 1913 |
| Historical significance | Generally credited as the first vitamin experimentally isolated and confirmed, hence the first letter |
| Letter designation adopted | 1916, by McCollum and Cornelia Kennedy, as part of an alphabetical naming system |
| Preformed vitamin A | Retinol and retinyl esters (e.g. retinyl acetate); animal-sourced; used directly by the body |
| Provitamin A | Carotenoids such as beta-carotene; plant-sourced; converted to active vitamin A as needed |
| Adult Reference Intake (EU) | 800mcg |
| Adult tolerable upper intake level, preformed (NIH ODS) | 3,000mcg per day |
| Bone/fracture association (NIH ODS) | Observed in studies at preformed intakes above ~1,500mcg/day; evidence mixed, no confirmed safe threshold |
| Daily Essentials | 400mcg (50% RI), as retinyl acetate, preformed |
| Inner Beauty | 10mg Betatene (beta-carotene), provitamin A, in the Collagen component |
Frequently Asked Questions
Why is vitamin A called vitamin A?
Because it's generally credited as the first vitamin ever experimentally isolated and confirmed to prevent a deficiency disease, by Elmer McCollum and Marguerite Davis at the University of Wisconsin–Madison, published in 1913. The alphabetical letter system that gave it the name "A" followed a few years later, in 1916.
What's the actual difference between retinol and beta-carotene?
Retinol is preformed vitamin A, found in animal-sourced foods, and the body absorbs and uses it directly. Beta-carotene is a provitamin A carotenoid, found in plant foods, and the body converts only as much of it into active vitamin A as it actually needs, through a self-regulating process.
Is vitamin A toxic?
Preformed vitamin A can be, at consistently excessive intakes. The NIH Office of Dietary Supplements sets the adult tolerable upper intake level at 3,000mcg per day. Provitamin A carotenoids like beta-carotene don't carry the same toxicity risk, since the body's own conversion process regulates how much active vitamin A actually gets made.
Does Daily Essentials or Inner Beauty use retinol?
Daily Essentials uses a preformed form, retinyl acetate, at 400mcg (50% of the Reference Intake). Inner Beauty uses a provitamin A form instead, 10mg of Betatene (beta-carotene), inside its Collagen component. Neither product uses undiluted, high-dose retinol.
The Takeaway
Vitamin A earned its place at the front of the alphabet by being the first vitamin science could actually isolate and prove, back in a University of Wisconsin lab in 1913, years before B, C, or D had names of their own. What's easy to miss is that "vitamin A" was never really one thing: it's a preformed form the body uses directly and stores, and a provitamin A form the body converts only as needed, and the two behave differently enough that the difference deserves to be on every label, not buried in it. Which form makes sense depends on the job a formula is doing, which is exactly why Daily Essentials and Inner Beauty make two different, equally reasonable choices about it.
Reviewed by Fatima Kassem - pharmacist and founder of Vitameenat, MSc in Pharmaceutical Sciences from the University of Copenhagen, with early career experience at Novo Nordisk.
