Vitamin A
Compiled from published pharmacological and botanical literature. Not independently verified by Herbuno. Spotted an error or have a correction? Flag it below →
| Compound | Vitamin A — preformed retinoids and provitamin A carotenoids |
|---|---|
| CAS | 68-26-8 (retinol) · 79-81-2 (retinyl palmitate) · 127-47-9 (retinyl acetate) |
| Unit conversion | 1 µg RAE = 1 µg retinol = 3.33 IU retinol activity |
| Carotenoid conversion | 12 µg dietary β-carotene = 1 µg RAE · 2 µg supplemental in oil = 1 µg RAE |
| Adult upper limit | 3,000 µg RAE/day preformed retinol — carotenoids excluded |
| Pregnancy | Preformed retinol is teratogenic at high intake; β-carotene is not |
| Claim strength | High for the teratogenicity and unit conversions; High for the smoker caution |
| Buy from Herbuno | Liposomal Vitamin A (Retinyl Palmitate) Powder · plain retinyl palmitate / retinyl acetate: availability on request |
| Origin | Processed / Sourced from India |
| MOQ | R&D 100 g / 250 g (subject to stock) · Pilot batch 1–5 kg · Bulk 10 kg, 25 kg and above |
| Lead Time | Dispatch within 72 hrs from stock · fresh-batch production (typically 50 kg+): 10 working days |
| Documentation | CoA & MSDS standard with every lot |
Name origin: The first vitamin assigned a letter, identified by McCollum and Davis in 1913 as a fat-soluble growth factor in butter and cod liver oil. "Retinol" records its function in the retina, where retinal, its aldehyde, is the chromophore of rhodopsin — the connection between vitamin A deficiency and night blindness being among the oldest recorded nutritional observations.
Why "vitamin A" is not a specification: The term covers two chemically and toxicologically distinct groups. Preformed vitamin A comprises the retinoids — retinol and its esters, retinyl palmitate and retinyl acetate — which are absorbed and stored efficiently and are teratogenic at high intake. Provitamin A carotenoids, principally beta-carotene, are converted to retinal with a regulated and saturable efficiency, are not teratogenic, and carry a separate and quite different safety issue of their own.
The unit problem: Vitamin A labelling carries two incompatible unit systems in simultaneous use. Retinol activity equivalents express the physiologically meaningful quantity: 1 microgram RAE equals 1 microgram of retinol, 12 micrograms of dietary beta-carotene, or 2 micrograms of supplemental beta-carotene in oil. International units are the older system, with 1 IU equal to 0.3 micrograms of retinol, so 1 microgram of retinol is 3.33 IU. The historical IU conversion for beta-carotene, 1 IU to 0.6 micrograms, assumed a conversion efficiency now considered too favourable, which is why RAE replaced it and why converting old figures produces errors.
Commercial source: Retinyl palmitate and retinyl acetate are produced by chemical synthesis; retinol itself is too unstable for most applications. Natural sources include fish liver oils. Beta-carotene is produced synthetically, by Blakeslea trispora fermentation, or extracted from Dunaliella salina algae or palm oil, and is a separate article.
Evidence for Vitamin A Applications
Preformed vitamin A is teratogenic at high intake, and this is the governing formulation constraint. Excess retinol in early pregnancy is associated with craniofacial, cardiac and central nervous system malformations, the relationship is well established from both the retinoid pharmaceutical experience and from nutritional epidemiology, and intakes above roughly 10,000 IU daily of preformed vitamin A have been treated as the threshold of concern. Pregnancy and prenatal products therefore either exclude preformed retinol or hold it well below that figure, and a pregnancy warning on a high-retinol product is a requirement rather than a precaution. Claim strength: High.
Beta-carotene is not teratogenic, which is the strongest argument for using it instead in pregnancy-adjacent formulation. Conversion of beta-carotene to retinal by beta-carotene 15,15'-oxygenase is regulated and down-regulates as vitamin A status rises, so excess carotenoid does not produce hypervitaminosis A. High intake produces carotenodermia, a harmless yellow-orange skin discolouration that resolves on withdrawal. For a prenatal or women's product, provitamin A is the safer route to vitamin A activity. Claim strength: High.
Beta-carotene carries its own serious caution, which runs in a different direction entirely. Two large randomised trials of beta-carotene supplementation, one in male smokers and one in smokers and asbestos-exposed workers, reported increased lung cancer incidence in the supplemented arms. The findings were unexpected, were consistent across the two trials, and changed the field's position on supplemental beta-carotene in smokers. Any beta-carotene product needs to account for this, and a high-dose beta-carotene product marketed to a population that includes smokers is contraindicated by trial evidence rather than by theory. Claim strength: High.
Hypervitaminosis A from preformed retinol is a real clinical entity and underpins the upper limit. Chronic excess produces hepatotoxicity with fibrosis, raised intracranial pressure with headache and visual disturbance, bone and skin changes, and hair loss; acute massive intake produces a distinct syndrome. Adult tolerable upper intake levels are commonly set at 3,000 micrograms RAE daily and apply to preformed vitamin A only, carotenoids being excluded because their conversion is regulated. Because retinol is stored in the liver, toxicity accumulates rather than depending on a single dose. Claim strength: High.
Deficiency remains the dominant global issue and the mechanism is specific. Vitamin A deficiency causes night blindness progressing to xerophthalmia and corneal destruction, and increases childhood infectious mortality; it is among the most prevalent micronutrient deficiencies worldwide and the leading preventable cause of childhood blindness. The retinal mechanism is direct: retinal is the rhodopsin chromophore, so inadequate supply degrades scotopic vision first. These are disease endpoints and inform public health fortification rather than supplement claims. Claim strength: High.
Ester form and stability determine the practical specification. Retinol is highly susceptible to oxidation and to light, and is generally unusable without esterification; retinyl palmitate and retinyl acetate are more stable and are the commercial articles, with palmitate the more common. Both still require an antioxidant system, light exclusion and often encapsulation. Potency loss over shelf life is a routine problem in multivitamins, where overage is standard practice, and it should rest on real stability data for the specific matrix rather than a generic figure. Claim strength: High.
Sourcing vitamin A from Herbuno. We hold retinyl palmitate in a liposomal format; beta-carotene and other carotenoids are separate articles.
Settle three things before formulating. Whether the product needs preformed retinol or provitamin A — for anything pregnancy-adjacent, beta-carotene is the safer route, since preformed retinol is teratogenic at high intake and carotenoid conversion is self-limiting. The unit system, in RAE with the IU equivalent stated, since converting historical IU figures for carotenoids produces errors. And the target population: beta-carotene is contraindicated at high dose in smokers on trial evidence. All lots ship with CoA and MSDS; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
Express the dose in retinol activity equivalents and give the IU figure alongside. Adult reference intakes sit around 700 to 900 micrograms RAE daily. The adult tolerable upper intake level of 3,000 micrograms RAE applies to preformed vitamin A only. Conversions: 1 microgram RAE equals 1 microgram retinol equals 3.33 IU of retinol activity; 1 microgram RAE equals 2 micrograms of supplemental beta-carotene in oil, or 12 micrograms of dietary beta-carotene. Do not convert historical beta-carotene IU figures forward, because the old 1 IU to 0.6 microgram basis assumed a conversion efficiency now considered too favourable.
The pregnancy decision should be made first because it determines the vitamer. Preformed retinol is teratogenic at high intake, with roughly 10,000 IU daily treated as the threshold of concern, so a prenatal or women's-health product either excludes preformed retinol, holds it well below that, or carries an explicit pregnancy warning. Beta-carotene avoids the issue entirely because conversion down-regulates with status. Where both are present, the preformed fraction is the one the limit applies to and it should be declared separately.
The smoker caution applies in the opposite direction and should be accounted for in beta-carotene products. Two large randomised trials reported increased lung cancer incidence with beta-carotene supplementation in smokers and asbestos-exposed workers. For a high-dose beta-carotene product this is trial evidence against use in that population, not a theoretical concern, and the target market should be considered at formulation. Dietary-level carotenoid from food is not implicated.
Stability is the dominant handling issue for the retinoids. Retinol is highly oxidation- and light-sensitive; retinyl palmitate and retinyl acetate are more stable but still require an antioxidant system, opaque packaging, nitrogen headspace where practical, and often beadlet encapsulation or liposomal delivery. Overage is standard practice in multivitamins, and the overage figure should come from accelerated and real-time stability data for the specific matrix — trace metals, ascorbate, minerals and moisture all accelerate loss, and a premix behaves differently from a single-vitamin system.
For analytical control, specify the vitamer and ester by CAS number, assay by HPLC with the basis stated in both RAE and IU, and the all-trans content, since isomerisation to 13-cis retinol and other geometric isomers reduces activity and is a marker of thermal and light history. Require the antioxidant system declared. Standard coverage includes heavy metals, residual solvents, microbiological limits and, for a beadlet or encapsulated form, the carrier and wall material identity, free or surface oil content, and particle size.
One labelling discipline prevents most of the errors in this category. Declare preformed vitamin A and provitamin A carotenoid separately, each in micrograms, then give the combined RAE total and the IU equivalent. That single convention resolves the teratogenicity limit, which applies only to the preformed fraction; the upper intake level, which likewise excludes carotenoids; the smoker caution, which applies only to supplemental beta-carotene; and the conversion ambiguity between the two unit systems. A label stating only "Vitamin A 5,000 IU" tells a formulator none of what they need and leaves the safety position indeterminate.
Frequently Asked Questions — Vitamin A
How do I convert IU to RAE?
For retinol: 1 microgram RAE = 1 microgram retinol = 3.33 IU. For supplemental beta-carotene in oil: 2 micrograms = 1 microgram RAE; dietary beta-carotene is 12 micrograms to 1. Do not convert historical beta-carotene IU figures forward — the old 1 IU to 0.6 microgram basis assumed a conversion efficiency now considered too favourable.
Can I put preformed vitamin A in a prenatal product?
Only with care, and often better not. Preformed retinol is teratogenic at high intake, with roughly 10,000 IU daily treated as the threshold of concern, and the association with craniofacial, cardiac and CNS malformations is well established. Either exclude it, hold it well below that, or carry an explicit pregnancy warning. Beta-carotene avoids the issue.
Why is beta-carotene safer there?
Because conversion is regulated. Beta-carotene 15,15'-oxygenase down-regulates as vitamin A status rises, so excess carotenoid does not produce hypervitaminosis A. High intake gives carotenodermia — a harmless yellow-orange skin discolouration that resolves on withdrawal. It is not teratogenic.
So beta-carotene has no safety issues?
It has a serious one, running the other way. Two large randomised trials of beta-carotene supplementation — one in male smokers, one in smokers and asbestos-exposed workers — reported increased lung cancer incidence in the supplemented arms. For a high-dose beta-carotene product that is trial evidence against use in smokers, not theory.
How should I declare it?
Preformed vitamin A and provitamin A carotenoid separately in micrograms, then the combined RAE total with the IU equivalent. That one convention resolves the teratogenicity limit, the upper intake level, the smoker caution and the unit ambiguity — all of which apply to one fraction and not the other. "Vitamin A 5,000 IU" alone leaves the safety position indeterminate.
What should I specify beyond assay?
All-trans content — isomerisation to 13-cis retinol and other geometric isomers reduces activity and marks thermal and light history. Also the ester by CAS number, the antioxidant system declared, and for a beadlet or encapsulated form the carrier and wall material, free or surface oil content, and particle size.