Not medical advice. I am a software engineer, not a physician. This page documents my own protocol and the research I read while building it. Talk to a qualified clinician before changing your supplementation, diet or any treatment. Lab reference ranges quoted here vary by laboratory and by individual.
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Vitamin A is a fat-soluble essential nutrient that exists in two primary forms: preformed retinol (from animal sources) and provitamin A carotenoids (from plants, primarily beta-carotene). The active forms — retinal, retinoic acid, and retinol — regulate over 500 genes and are critical for immune function, vision, reproduction, and cellular differentiation. Preformed retinol is the preferred supplemental form because the conversion of beta-carotene to retinol is highly variable (some individuals convert as little as 3% due to BCO1 gene polymorphisms), making plant-based sources unreliable for achieving adequate vitamin A status.
Retinoic acid is the master regulator of mucosal immune responses. It drives the differentiation of naive T-cells into gut-homing regulatory T-cells, promotes IgA antibody class-switching in B-cells, and maintains the integrity of epithelial barriers in the respiratory tract, gut, and urogenital system. Vitamin A deficiency impairs these barriers and reduces secretory IgA, the first-line antibody defense at mucosal surfaces. This is why vitamin A deficiency dramatically increases susceptibility to respiratory and gastrointestinal infections.
Retinal (the aldehyde form of vitamin A) is the chromophore in rhodopsin, the photopigment in rod cells responsible for low-light vision. When light strikes rhodopsin, 11-cis-retinal isomerizes to all-trans-retinal, triggering the phototransduction cascade that converts light into neural signals. The retinal must then be recycled back to 11-cis form through the visual cycle. Vitamin A deficiency causes night blindness (nyctalopia) as the first clinical sign, progressing to xerophthalmia and irreversible corneal damage if unaddressed.
Retinoic acid binds to nuclear receptors (RAR and RXR) that function as transcription factors, directly regulating the expression of over 500 genes involved in cell proliferation, differentiation, and apoptosis. In the skin, this drives keratinocyte turnover, normalizes desquamation, reduces sebum production, and promotes organized collagen deposition. This is the mechanism behind retinoids being the gold-standard dermatological treatment for acne, photoaging, and hyperpigmentation.
Toxicity note: Vitamin A is fat-soluble and can accumulate in the liver. At 10,000 IU (3,000 mcg RAE) daily, toxicity risk is very low in healthy adults. However, regular liver panel monitoring is recommended, especially with long-term use. Pregnant women should not exceed 3,000 IU due to teratogenic risk of high-dose retinol.
| Parameter | Detail |
|---|---|
| Product | NOW Foods Vitamin A |
| Dose | 3,000 mcg RAE (10,000 IU) |
| Timing | With breakfast (fat-containing meal for absorption) |
| Form | Retinol (preformed vitamin A) in softgel |
| Duration | Daily, ongoing |
See the full supplement stack for timing relative to other supplements and meals.
Semba, R. D. (1999). Vitamin A and immunity to viral, bacterial and protozoan infections. Proc Nutr Soc, 58(3), 719-727. — Establishes vitamin A as critical for maintaining mucosal barriers and IgA production; deficiency increases infection susceptibility across respiratory, gastrointestinal, and urogenital systems. PubMed 11375434
Travis, G. H., et al. (2007). Diseases caused by defects in the visual cycle retinoid regeneration. Ann Rev Pharmacol Toxicol, 47, 469-512. — Detailed review of the visual cycle and how retinal (vitamin A aldehyde) functions as the chromophore in rhodopsin for phototransduction. PubMed 17536128
Zasada, M., & Budzisz, E. (2019). Retinoids: active molecules influencing skin structure formation in cosmetic and dermatological treatments. Postepy Dermatol Alergol, 36(4), 392-397. — Reviews retinoid mechanisms in skin: keratinocyte differentiation, collagen synthesis stimulation, MMP inhibition, and melanogenesis regulation. PubMed 22254103
| Test | Why It Matters | Link |
|---|---|---|
| Liver Panel (ALT, AST, GGT) | Vitamin A is stored in hepatic stellate cells; monitoring liver enzymes is how accumulation-related hepatotoxicity at 10,000 IU daily would be detected. 10,000 IU is at the established upper intake level for adults, so do not stack it with another retinol source, and do not take it at all if you are pregnant or may become pregnant — preformed vitamin A is teratogenic | Lab Tests |
| Vitamin A (Retinol, serum) | Direct measurement of circulating retinol; optimal range 40-60 mcg/dL. Levels below 30 indicate deficiency; above 100 suggest excess | Lab Tests |
A 2025 review in the International Journal of Molecular Sciences examined vitamin A's role in autoimmune and immune-mediated diseases, finding that vitamin C deficiency (often co-occurring with vitamin A deficiency) is common in conditions such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes, and Hashimoto's thyroiditis. Research from 2025 demonstrated that skin microbiota encode enzymes capable of interconverting vitamin A derivatives, with host-microbe-retinoid interactions increasingly recognized as key determinants of epithelial function and therapeutic response. A January 2025 systematic review consolidating evidence on alternative vitamin C formulations noted that calcium ascorbate EC showed favorable impacts on immune parameters and association with fewer colds. For topical vitamin A, retinal (retinaldehyde) achieved approximately 25% higher skin penetration and 35% greater wrinkle depth reduction compared to retinol in 12-week studies, being 10x more bioavailable than other forms of vitamin A.
NOW Foods Vitamin A — 10,000 IU (3,000 mcg RAE), 100 softgels. Price: $5.37. Buy on iHerb