Chicago researchers found that vitamin B3, commonly known as niacin, may protect against the mental ravages of age-- and the associated with aging.

The B vitamins consist of thiamin (B1), riboflavin (B2), niacin, pyridoxine (B6), folic acid, pantothenic acid, biotin, and cobalamin (B12). Also included is choline, a nutrient found in eggs that is needed to produce cell membranes and may slow age-related loss.

All the Bs play a critical role in brain function, from manufacturing neurotransmitters to regulating energy release in brain cells. Niacin seems to have a particularly potent role in maintaining mental agility.

At the Rush Institute for Healthy Aging in Chicago, Martha C. Morris monitored the health and dietary status of 815 adults age 65 and older for six years. None had Alzheimer's disease at the start of the study; six years later, 131 did.

Those with the lowest food intake of niacin were 80 percent more likely to be diagnosed with Alzheimer's disease than those with the highest intake. The rate of cognitive decline among the high-niacin eaters was almost half (44 percent) that of those consuming less niacin.

Just what does niacin do? Other studies have shown that it helps in the synthesis and repair of and that it plays a role in signaling between nerve cells. It also acts as a potent in brain cells.

Severe deficiencies of several B vitamins have been shown to have profound effects on the brain, leading to abnormal brain waves, detectable as abnormalities on EEGs; impaired memory; and higher levels of , confusion, irritability, and . Even marginal deficiencies of B vitamins can cause EEG disturbances and inhibit mental performance.

Fatigue, irritability, poor , anxiety and depression--all can be signs of a B vitamin deficiency. That's because compounds in the B complex are needed for everything from the healthy maintenance of brain cells to the metabolism of carbohydrates, the brain's source of fuel. Bs are also necessary for production of neurotransmitters, which regulate mood and conduct messages through the brain.

Thiamin deficiency is known to hamper the brain's ability to use glucose, decreasing energy available for mental activities. It also overexcites neurons so that they fire endlessly, poop out, and die. Being only marginally deficient in thiamin may nevertheless slow down your brainpower at any age.

Folic acid helps maintain normal levels of serotonin. Deficiencies contribute to depression, , and . In a study of depressed patients taking lithium, those also given folic acid supplements for a year showed dramatic relief of depression, compared to those given no supplements.

B6 and B12 contribute to the myelin sheath around nerve cells, which speeds signals through the brain. B12 and folic acid together are needed for making normal cells, including blood cells. Inadequate B12, found only in animal products, or folic acid can yield blood cells unable to carry vital oxygen to the brain.

These three Bs aid in the manufacture of the excitatory neurotransmitter GABA, as well as serotonin and , neurotransmitters that regulate mood. All three neurotransmitters interregulate each other, but the ways they work in concert or against each other are only beginning to be understood.

Choline, found in protein-rich food such as eggs, is needed by everyone for the production of cell membranes and for making the neurotransmitter acetylcholine, which affects memory. Pregnant women must also consume choline to support the rapid production of fetal brain cells. Studies have shown that a with four times the normal amount of choline during can actually prevent memory decline in offspring as they reach old age. Supplemented animals also have superior memory throughout their own lives.

Which B is most important? It's impossible to say. They all have important roles. And a deficiency of one is likely to hamper the effectiveness of the others. Only rarely are the effects of a B vitamin deficiency clear-cut. A varied, healthy diet of lean meats, colorful vegetables and whole grains will usually cover the bases.