By Willow Lawson, published on April 2, 2003 - last reviewed on June 9, 2016
B vitamins are often called the energy vitamins, but they are more like keys that unlock it.
Fatigue, irritability, poor concentration, 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.
The B complex includes B1 (thiamine), B2 (riboflavin), B3 (niacin), B6, pantothenic acid, biotin, B12 and folate, also known as folic acid on vitamin bottles. It also includes choline, a nutrient found in eggs that is needed to produce cell membranes and may slow age-related memory loss.
Which B is most important? It's impossible to say.
"They all have important roles," says Roxanne Moore, a registered dietitian at the Maryland Department of Education and a spokeswoman for the American Dietetic Association. A varied, healthy diet of lean meats, colorful vegetables and whole grains will usually cover the bases.
The subgroup of B6, B12 and folate is the subject of much research. Sufficient intake lowers rates of birth defects, cardiovascular disease, depression, dementia and Alzheimer's disease. The three work together and even marginal deficiencies have large effects.
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 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 dopamine, 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.
Only rarely are the effects of a B vitamin deficiency clear-cut. The Centers for Disease Control reported that two children had severe motor and language skill delays because of a deficiency in vitamin B12. They had both been breastfed by vegan mothers who were also deficient in B12.
The vitamin occurs naturally only in animal products, although many cereal and soy products are fortified with B12, among others. Both children quickly improved after eating a new diet, but both also had lingering language and motor problems a year after treatment.
"The problem doesn't affect just vegetarians," says Maria Elena Jefferds, Ph.D., a CDC epidemiologist. "There are plenty of non-vegan Americans who don't pay enough attention to what they eat and lack basic nutrients."
The key is a varied diet. The importance of some nutrients is only now emerging.
Choline is one that shows promise. Found in protein-rich food such as eggs, it 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.
Pregnancy may prove to be the most decisive period for many nutrients. Animal studies by Duke University neuroscientist Christina Williams, Ph.D., have shown that a diet with four times the normal amount of choline during pregnancy can actually prevent memory decline in offspring as they reach old age. Supplemented animals also have superior memory throughout their own lives.
"Early choline supplementation actually changes the brain, altering the structure and the functioning," says Williams. "We were astounded by such a big affect."
Choline was added to the government list of essential nutrients in 1998. Data from the Human Genome Project may show that we all have a "nutrient genotype." "It may all come down to sluggish enzymes," says Williams. "It may be that most people eat enough choline, but some people can't use it."