"Be careful about reading health books. You may die of a misprint." - Mark Twain

Many vitamins are essential players in the natural biochemistry of your body. B vitamins are particularly important for proper functioning of your brain and nervous system. Although you can sometimes buy each vitamin by itself in a health food store, it is best to take B vitamins together. Doctors refer to them as B complex vitamins to emphasize their interactions and interdependence.

Many of the B vitamins were discovered and eventually isolated during the first half of the 1900's. They include B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 pantothenic acid, B6 (pyridoxine), B12 (cobalamin), folic acid or folate, and biotin.

These vitamins are water-soluble and are known in more technical terms as "coenzymes." That is, they help the enzymes of the body properly run the biochemical reactions we need to operate the functions of our cells. Food sources of B vitamins include whole grains, nuts, liver, red meats, green leafy vegetables, and brewer's yeast.

For instance, B1 or thiamine is important for the proper utilization of carbohydrates in the diet. B6 or pyridoxine is essential for processing the amino acids from proteins in the diet. In addition to iron deficiency anemia, lack of adequate amounts of certain B vitamins, such as B6, B12, and/or folate, can itself lead to different kinds of anemias, with fatigue, weakness, and poor tolerance of exercise. Alcoholics often deplete their supplies of thiamine and folic acid, making it essential to include vitamin repletion in treatment for this common and serious problem.

B vitamins play a major role in proper functioning of the nervous system. Low levels of B vitamins such as B6 can impair the ability to synthesize common brain transmitters such as serotonin, norepinephrine, and dopamine. This is the kind of situation when taking a drug for depression, for instance, may not help as much as it could, because of the brain's inability to make the brain chemicals that the drug works on. Inadequate B6 can even lead to seizures in severe cases.

In older people especially, low levels of B vitamins can lead to poorer cognitive (thinking) abilities. People at the lowest levels of several B vitamins in their diet and/or blood levels have the poorest memory and general cognitive function. Some people lose the ability to absorb B12 because of changes in their stomach and manufacture of intrinsic factor, which is necessary for B12 absorption. People who can't make intrinsic factor typically need B12 shots to get the vitamin into their bodies.

Many other people, however, as they age, lose the ability to make stomach acid. They have intrinsic factor to absorb B12, but the low acid condition in their stomach makes it hard to release the B12 from foods. In this situation, taking B12 supplements by mouth in capsules or tablets that dissolve easily or via liquid supplements can replace the body levels of the vitamin without needing shots in most cases.

In recent years, there has been increased interest in folate, B12, and B6, which are important in different steps for processing and detoxifying the amino acid homocysteine. Homocysteine can build up in the bloodstream and cause damage to blood vessels. In addition to cholesterol, homocysteine is a risk factor for heart disease, stroke, and Alzheimer's disease. The good news is that taking supplements of folate, B12, and B6 can often lower elevated levels of homocysteine and perhaps side-step or at least delay or lessen the health risks.

Many people do not realize how interactive the body's biochemistry really is. For instance, thyroid hormone regulates use of vitamin B2. In turn, vitamin B2 is needed to catalyze a reaction that generates the active form of vitamin B6. To clear out homocysteine, there are many metabolic steps, some of which require adequate amounts of B6, folate, and B12. In other words, the B complex vitamins are part of a biochemical network. Pushing the dose of any single vitamin might imbalance the interactions with the rest of the network. So, the bottom line at this point is to take a good multivitamin including all of the B complex vitamins in adequate amounts (at least the recommended daily allowance and perhaps a bit more).

Be careful of excess B vitamins. Although they are water soluble, high doses of B6 (200 mg or so per day for many months) can cause damage to peripheral nerves. Daily doses around 10-25 mg/day are probably OK for most people (but consult your physician for your own case). Excess folate can lead to insomnia and/or GI distress. People probably need somewhere between the RDA of 0.4 mg and the amount suggested for pregnant women to prevent the birth defect of spina bifida, of 0.8 mg/day. Higher doses may over-activate the nervous system and cause insomnia or irritability.

So, more is not always better, but the right amount for you is essential. In the world of complex interactions in networks, linear relationships are not common. Think instead of an upside down or inverted U shaped graph - too little or too much is bad, but somewhere in the middle is just right.

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