TABLE 1.
Summary of studies to determine a conversion factor for β-carotene in food sources to vitamin A1
| Food matrix | Method | Dose | Conversion factor (by weight) | Reference |
| Fruit, n = 49; vegetables, n = 45; retinol-rich foods, n = 48 (ages 7–11 y) | Changes of serum retinol concentration in vitamin A–deficient (≈0.7 μmol/L) anemic schoolchildren | Fruit: 509 RE/d; vegetables: 684 RE/d; vitamin A–rich foods: 556 RE/d | 12:1 26:1 | 16 |
| Green/yellow vegetables, n = 10; light-colored vegetables, n = 8 | Total body stores of vitamin A before and after the vegetable intervention in schoolchildren (aged 5.3–6.5 y) with normal or marginal vitamin A status | Green/yellow vegetables (206 mg calculated trans-β-carotene) to prevent the decrease of 7.7 mg in liver stores | 27:1 | 18 |
| Sweet potato, Indian spinach, β-carotene capsule, or retinyl palmitate; all, n = 14 | Mean changes of total body stores of vitamin A before and after a 60-d intervention in adult men compared with the mean changes in the retinyl palmitate group | Sweet potato: 750 μg RE; Indian spinach: 750 μg RE; β-carotene capsule: 750 μg RE; retinyl palmitate: 750 μg RE | 13:1 10:1 6:1 | 15 |
| [2H]-Labeled spinach, and vitamin A in oil capsule, n = 14 | Comparison of AUC responses to the spinach and the vitamin A reference dose in adults | Calculated 11 mg trans-β-carotene from 300 g pureed, cooked spinach, and 3 mg [2H8]-vitamin A | 21:1 | 19 |
| [2H]-Labeled carrot, and vitamin A in oil capsule, n = 7 | Comparison of AUC responses to the carrot and the vitamin A reference dose in adults | Calculated 11 mg trans-β-carotene from 100 g pureed, cooked carrot, and 3 mg [2H8]-vitamin A | 15:1 | 19 |
| Fruit, n = 69; leafy vegetables, n = 70; retinol-rich foods, n = 70; control, n = 68 | Changes of serum retinol concentration in lactating women after they ate fruit or vegetables, or took preformed vitamin A | Fruit: 4.8 mg trans-β-carotene; vegetables: 5.6 mg trans-β-carotene; retinol-rich diet: 610 μg retinol; control: 0.6 mg β-carotene and 1 μg retinol | 12:1 28:1 | 17 |
| Spirulina powder, n = 10 | Comparison of AUC responses to the Spirulina and the vitamin A reference dose in adults | 4.3 mg Spirulina trans-β-carotene | 4.5:1 | 31 |
| Golden Rice, n = 5 | Comparison of AUC responses to a Golden Rice meal and the vitamin A reference dose in adults | Rice meal that contained 1–1.5 mg rice β-carotene | 3.6:1 | 32 |
1
RE, retinol equivalents; AUC, area under the curve.