Solgar Vitamin B-12 1000 mcg plays a role in blood building, iron absorption and the conversion of folic acid. Vitamin B-12 is a methyl donor and therefore helps to lower homocysteine levels in the blood. Vitamin B-12 is good for memory. The absorption of vitamin B-12 depends on stomach acid and intrinsic factor. In the elderly and people who use gastric acid inhibitors, the absorption is often reduced, so that high doses (minimum 500 mcg) are required.