New research has shown that B vitamins play a key role in how the brain functions.

The studies, which were spearheaded by the U.S. Department of Agriculture and conducted by scientists at the University of California-San Francisco, included more than 1,800 Hispanic seniors, aged 60 to 101.

In one, an analysis of volunteers’ blood samples showed that lower levels of one B vitamin, folate, were associated with symptoms of dementia and poor brain function, also called “cognitive decline," as determined by standard tests of memory and other factors.

It also showed that women with low levels of folate were more likely to suffer from depression, compared to those with higher levels of the vitamin.

In research with vitamin B-12, scientists determined that a protein known as holoTC, short for holotranscobalamin, might be key to a new approach for detecting cognitive decline earlier and more accurately.

B vitamins include B-6, B-12 and folate. Dietary sources include bell peppers, romaine lettuce, spinach, tuna, meats, beans and fish, such as salmon, cod, halibut and snapper.

They are also widely available in nutritional supplement form.