Among several factors likely to affect an individual's requirement for vitamin B6, protein intake has been the most studied. Increased dietary protein results in an increased requirement for vitamin B6, probably because PLP is a coenzyme for many enzymes involved in amino acid metabolism (32).
In 1993, the European Scientific Committee for Food set population reference intakes (PRI) for vitamin B6 (pyridoxine) in milligrams (mg) per day (33):
| Age | Males: mg/day | Females: mg/day |
| 6–12 months | 0.4 | 0.4 |
| 1–3 years | 0.7 | 0.7 |
| 4–6 years | 0.9 | 0.9 |
| 7–10 years | 1.1 | 1.1 |
| 11–14 years | 1.3 | 1.1 |
| 15–17 years | 1.5 | 1.1 |
| 18 years and older | 1.5 | 1.1 |
| Pregnant | - | 1.3 |
| Breast-feeding | - | 1.4 |
In 1998, the U.S. Food and Nutrition Board of the Institute of Medicine set a recommended dietary allowance (RDA) for vitamin B6, which does not consider protein intake (34):
| Life Stage | Age | Males: (mg/day) | Females: (mg/day) |
| Infants | 0–6 months | 0.1 (AI) | 0.1 (AI) |
| Infants | 7–12 months | 0.3 (AI) | 0.3 (AI) |
| Children | 1–3 years | 0.5 | 0.5 |
| Children | 4–8 years | 0.6 | 0.6 |
| Children | 9–13 years | 1.0 | 1.0 |
| Adolescents | 14–18 years | 1.3 | 1.2 |
| Adults | 19 - 50 years | 1.3 | 1.3 |
| Adults | 51 years and older | 1.7 | 1.5 |
| Pregnancy | all ages | - | 1.9 |
| Breast-feeding | all ages | - | 2.0 |
Metabolic studies suggest that young women require 0.02 mg vitamin B6 per gram of protein consumed daily (32, 35, 36). Using the upper boundary for acceptable levels of protein intake for women (100 g/day), the daily vitamin B6 requirement for young women would be calculated at 2.0 mg. Other metabolic studies have also indicated that the requirement for vitamin B6 in (older) adults is approximately 2.0 mg daily (37).
Although a vitamin B6 intake of 2.0 mg daily is slightly higher than the most recent RDA, it is 50 times less than the tolerable upper intake level (7) (see Safety).
Since for the human body cannot store vitamin B6, a continuous daily intake is essential.
For a detailed overview of recommended daily intakes (PRIs/RDAs) of vitamins and minerals for adults derived from different countries and organizations see PDF.