Final answer:
Individuals over 50 are often advised to supplement with cobalamin (B12) because of decreased stomach acid production and intrinsic factor, which are essential for its absorption.
Step-by-step explanation:
People over the age of 50 are encouraged to take a supplement of cobalamin (B12) due to the decrease in stomach acid production with age, required for its absorption. As people age, the production of intrinsic factor in the stomach, which is necessary for the absorption of vitamin B12, may decrease. Vitamin B12 is essential for the normal maturation and development of erythrocytes, necessary for the synthesis of DNA, and required for the conversion of methyl malonyl-CoA to succinyl-CoA.