What is the original name of vitamin A?

January 13, 2026 •

4 min read

In the early 20th century, researchers identified an essential growth-promoting substance and termed it "fat-soluble A". This initial discovery is the answer to what is the original name of vitamin A, a nutrient we now commonly know as retinol.

Quick Summary

The original name for vitamin A was "fat-soluble A," a classification coined in 1918 by researchers who found it was an essential growth-supporting factor present in certain fats.

Key Points

Original Name: The original name of vitamin A was "fat-soluble A," coined in 1918 by Elmer McCollum and Marguerite Davis during their research on essential nutrients.
Source of "Retinol" Name: The name retinol comes from the compound's crucial role in producing pigments within the retina of the eye, essential for vision.
Different Forms: Vitamin A is a collective term for a group of compounds called retinoids, which includes active forms like retinol and precursors such as beta-carotene.
Food Sources: Preformed vitamin A (retinol) is found in animal products, while provitamin A (carotenoids like beta-carotene) is sourced from plants.
Excessive Intake Risk: As a fat-soluble vitamin stored in the liver, excessive intake of preformed retinol can lead to toxicity, unlike provitamin A carotenoids.
Alphabetical Naming: The initial naming of vitamin A and B was a basic alphabetical system for categorizing essential factors based on their solubility.

The Early Discoveries and the "Accessory Factors"

Before vitamins were fully understood, scientists in the early 1900s observed that diets of only protein, fat, and carbohydrates were insufficient for health. Frederick Gowland Hopkins noted that milk contained necessary "accessory factors". Elmer McCollum and Marguerite Davis confirmed this, showing that rats thrived on butterfat or egg yolk but not lard or olive oil, leading them to propose a fat-soluble, growth-supporting factor. Around 1918, this factor was named "fat-soluble A," establishing the original name of vitamin A.

The Naming Convention of Early Vitamins

Early biochemists, including Casimir Funk who coined "vitamine" in 1912, developed an alphabetical system for naming these newly discovered essential nutrients. McCollum's fat-soluble substance was the first in this series, thus designated 'A'.

Funk's "Vitamines": The term combined "vital" and "amine," reflecting a belief that these compounds contained nitrogen. The 'e' was removed later when this wasn't universally true.
McCollum's Classification: McCollum's work led to the distinction between "fat-soluble A" and "water-soluble B," foundational to vitamin nomenclature.
Chemical vs. Trivial Name: While chemical names exist, the simple alphabetical system made it easier for public and early scientific reference.

The Transition to Retinol

Following its identification, scientists worked to isolate and describe the chemical structure of "fat-soluble A." Paul Karrer detailed the structure in 1932. The name retinol was later adopted, referencing the vitamin's critical function in the retina of the eye, where it's vital for producing light-absorbing pigments. Harry Holmes and Ruth Corbet isolated and crystallized vitamin A in 1937, contributing further to its chemical understanding. This progression from a functional description to a name based on chemical structure and biological role highlights the advancement of nutritional science.

The Different Forms of Vitamin A (Retinoids)

Today, vitamin A refers to retinoids, a group of fat-soluble compounds that include retinol, retinal, and retinoic acid, each with different roles. Dietary sources are classified as preformed vitamin A or provitamin A.

Preformed Vitamin A (Retinoids)

These active forms are found in animal products and can be used directly by the body. Sources include:

Liver
Fish and fish oils
Dairy products
Eggs

Provitamin A (Carotenoids)

Found in plants, carotenoids are converted into retinol in the body. Beta-carotene is a key example. Sources include:

Carrots
Sweet potatoes
Spinach and dark leafy greens
Red and yellow produce

Comparison of Preformed Vitamin A (Retinol) and Provitamin A (Beta-Carotene)


Feature	Preformed Vitamin A (Retinol)	Provitamin A (Beta-Carotene)
Source	Animal-based foods (liver, dairy)	Plant-based foods (carrots, spinach)
Bioavailability	High; readily absorbed and used by the body	Varies; must be converted to retinol by the body
Conversion	No conversion needed; already in active form	Converted to retinol in the body via specific enzymes
Toxicity Risk	High; excessive intake can lead to hypervitaminosis A as it is stored in the liver	Low; excess typically results in harmless yellowing of the skin (carotenodermia)
Antioxidant Role	Does not have significant antioxidant activity	Functions as an antioxidant, protecting cells from damage

Conclusion: From "Fat-Soluble A" to a Household Name

The journey of vitamin A from "fat-soluble A" to "retinol" reflects the evolution of scientific understanding, moving from observing nutritional effects to identifying specific compounds and their functions. While the original name is historical, vitamin A's importance for vision, immunity, and health remains critical. For further details, consult authoritative sources like the National Institutes of Health's fact sheet on vitamin A.

Frequently Asked Questions (FAQs)

What was the first vitamin discovered?

Vitamin A was one of the first essential nutrients identified, initially called "fat-soluble A".

Why is vitamin A also called retinol?

"Retinol" comes from the retina of the eye, highlighting its role in vision.

Who were the main researchers involved in the discovery of vitamin A?

Key researchers include Frederick Gowland Hopkins, and Elmer McCollum and Marguerite Davis.

Is retinol the same as vitamin A?

Retinol is the most active form, while vitamin A refers to a group of retinoids.

Is beta-carotene the same as vitamin A?

Beta-carotene is a provitamin A precursor converted to retinol in the body.

What are the different forms of vitamin A?

The main forms are retinoids like retinol, retinal, and retinoic acid.

How did the "e" get dropped from the term "vitamine"?

The 'e' was removed when it was found not all vitamins were nitrogen-based amines.

Why were vitamins originally named with letters?

The alphabetical naming was an early system based on solubility and discovery order.

Frequently Asked Questions

While not the first to be isolated, vitamin A was one of the first essential nutrients identified and distinguished from water-soluble factors, initially referred to as "fat-soluble A".

The name "retinol" is derived from the retina of the eye because the vitamin is essential for producing the light-absorbing pigments needed for vision, especially in low light.

Key discoveries were made by Frederick Gowland Hopkins, who identified "accessory factors," and later, Elmer McCollum and Marguerite Davis, who isolated the fat-soluble factor and named it "fat-soluble A".

Retinol is the most active and usable form of vitamin A, found in animal products. The broader term "vitamin A" refers to a group of related compounds called retinoids, of which retinol is a member.

Beta-carotene is a provitamin A, which means it is a precursor found in plants. The human body converts beta-carotene into retinol to use it as vitamin A.

The main forms of vitamin A are retinoids, which include retinol, retinal (retinaldehyde), and retinoic acid. Retinyl esters are the storage form in the liver.

Chemist Casimir Funk coined the term "vitamine" based on his theory that these compounds were "vital amines." The 'e' was later dropped when it was discovered that not all vitamins contained nitrogen-based amine groups.

The alphabetical naming was a simple convention adopted in the early 20th century to categorize vitamins in the order of their discovery, starting with "fat-soluble A" and "water-soluble B".