Vitamin B-12 helps maintain healthy nerve cells and red blood cells. Vitamin B-12 deficiency — most common in older adults and vegetarians — can cause various signs and symptoms, including memory loss. In these cases, vitamin B-12 supplements can help improve memory.

Aside from treating vitamin B-12 deficiency, there's no clear evidence that vitamin B-12 supplements improve memory for people with Alzheimer's disease.

Some studies suggest low vitamin B-12 levels may be associated with an increased risk of dementia. But supplementation with B vitamins has not been shown to improve brain function or symptoms of memory loss.

Regardless of its role in memory, vitamin B-12 remains an important part of a healthy diet.

Vitamin B-12 is found naturally in foods that come from animals, including fish, meat and poultry. Many breakfast cereals are fortified with vitamin B-12.

If you're concerned that you're not getting enough vitamin B-12 or other specific nutrients, consult your doctor — especially if you're an older adult or a vegetarian.