The most reliable data for establishing the Estimated Average Requirement (EAR) for vitamin B12 would be option e, which includes both serum vitamin B12 concentration (option a) and transcobalamin III (option c). Combining these two measures provides a more comprehensive assessment of vitamin B12 status.
Serum vitamin B12 concentration reflects the level of vitamin B12 in the blood, and it is commonly used as an indicator of B12 status. Transcobalamin III (also known as transcobalamin-1 or haptocorrin) is a protein that transports vitamin B12 in the blood. By considering both the concentration of vitamin B12 in the serum and the levels of transcobalamin III, a more accurate assessment of vitamin B12 status can be obtained.
Erythrocyte count (option b) and plasma gamma glutamyl hydrolase (option d) are not directly related to vitamin B12 status and are not commonly used as specific markers for assessing B12 adequacy. Therefore, they may not yield reliable data for establishing the EAR for vitamin B12.