English version in progress: interface and data are in English; some explanatory text is still in Chinese.
Vitamin A
维生素 A 在视网膜里变成视黄醛，和蛋白结合成"感光色素"视紫红质。
Full ranking Dose tool Products (4,134)
Key facts
Daily Value (US FDA)900 mcg
Tolerable Upper Intake Level (UL)3,000 mcg
Median（Per day）750 mcgP5 60 – P95 4,615
Products4,134
Sources: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/ · FDA DV 900 mcg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [1500] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); adult UL 3000 mcg; hard_high=30000 per serving (UL x10 or market maximum), hard_low=DV/1000
How it works：维生素 A 怎样帮助看清暗处？
- 食物里有两类：动物性的预成型维生素 A（视黄醇）和植物中的维生素 A 原（如 β-胡萝卜素）。标签用 RAE 统一换算。
- 吸收后主要储存在肝脏。
- 在视网膜中，视黄醛与视蛋白结合成视紫红质，负责弱光下的视觉。
- 视黄酸调控基因表达，参与细胞分化和免疫功能。
Schematic only; positions and scale are not anatomical.
Limits and cautions：预成型维生素 A 的成人 UL 为 3,000 mcg RAE/天，孕期超量可致畸；β-胡萝卜素不计入 UL。
Sources：NIH ODS: VitaminA Fact Sheet for Health Professionals
Daily dose across products（mcg/day）
DV 900
UL 3,000
16.5 mcglog scale · n=4,13412,000 mcg
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
| Form | Products | Median | P5–P95 | Elemental fraction |
|---|---|---|---|---|
| Retinyl palmitate | 1758 | 650 mcg | 90 – 3,000 | — |
| Beta-carotene (supplemental) | 1500 | 1,050 mcg | 65 – 3,750 | — |
| Retinyl acetate | 688 | 1,380 mcg | 200 – 9,240 | — |
| Retinol | 39 | 600 mcg | 30 – 3,000 | — |
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | Nature's Sunshine | Vitamin A & D | 1,050 mcg | 90.0 |
| 2 | Vitamin World | Beta-Carotene Provitamin A 10,000 IU | 3,000 mcg | 88.0 |
| 2 | The Vitamin Shoppe | Dry A 10,000 IU | 3,000 mcg | 88.0 |
| 2 | Nature's Bounty | Vitamin A & D3 | 3,000 mcg | 88.0 |
| 2 | Vitamin World | Vitamin A 10,000 IU | 3,000 mcg | 88.0 |
For information only; not medical advice. Talk to a doctor or pharmacist before starting or stopping any supplement.