Further evidence on the effects of vitamin B 12 and folate levels on episodic memory functioning: a population-based study of healthy very old adults

Abstract

Background: The relationship between vitamin status and cognitive functioning has been addressed in several recent studies with inconclusive results. The purpose of this study was to examine separate and combined effects of serum vitamin B 12 and folic acid on episodic memory functioning in very old age. Methods: Four study groups were selected from a population-based sample of healthy very old adults (90–101 years of age): normal B 12/normal folic acid, low B 12 /normal folic acid, normal B 12/low folic acid, and low B 12 /low folic acid. Cutoff levels were set at 180 pmol/L for vitamin B 12 and at 13 nmol/L for folic acid. Subjects completed two episodic recall tasks (objects and words) and two episodic recognition tasks (faces and words). Results: Neither vitamin affected recognition or primary memory. Most interesting, although B 12 was unrelated to recall performance, subjects with low folic acid levels showed impairment in both word recall and object recall. Conclusions: These results replicate and extend previous findings that folic acid may be more critical than B 12 to memory functioning in late life. The selective effects of folic acid on episodic recall were discussed in terms of encoding and retrieval mechanisms, as well as in relation to brain protein synthesis.