What's in a B-complex vitamin?

Q:    How many B vitamins make up a B-complex vitamin? Some B-complex products contain 4 different B vitamins, like B1, B2, B3, and B6, while others also include B-12.

There is no standard or official formula for what a B-complex vitamin should contain. That’s because “B-complex” was a term that wasn’t meant to describe any particular grouping of B vitamins. A vitamin formulation labeled as B-complex may contain any number of the eleven different B vitamins in various doses and combinations.

Although we are used to thinking about vitamins as having an alphabetical designation, like vitamins A, C, D, and E, not all B vitamins are referred to by a number. Although B-1 and B-6 are obviously B vitamins, they have other names too. For example, B-1 is also referred to as thiamine, and the vitamin named B-6 is also called pyridoxine.

There are other B vitamins, too, but you may not realize what they are because they have "plain" names, like folic acid, biotin, and pantothenic acid.

When scientists began discovering critical nutrients needed by our bodies, they called these newly discovered compounds "vitamins ." The first vitamin identified was a fat-soluble compound that researchers named Vitamin A. Next found were two water-soluble compounds, christened vitamin B and vitamin C.

Then, in 1930, the scientists hit a snag. Although vitamins A and C were easy to identify as single compounds, vitamin B was much more complex. Initially identified as one specific molecule, vitamin B turned out to be much more: a cluster of several unique compounds. Instead of having one particular vitamin B, scientists ended up isolating, identifying and naming one “vitamin B” component after another.

When the first individual B vitamin was identified, it was called vitamin B-1, or thiamine. This was followed by the discovery of a second B vitamin, called Vitamin B-2, or riboflavin. A third vitamin entity, B-3, is even more complex, with 4 different names: nicotinic acid, nicotinamide, niacin, and niacinamide.

After it was accepted that vitamin B was not a single compound, scientists referred to it as "B-complex" to express the potential of more than one vitamin that might be considered a B vitamin. Over time, several more specific vitamin B nutrients were isolated, but they weren't always given a "B" designation.

Eventually, 11 different vitamins were found inside the initial "vitamin B" compound. All eleven B vitamins are water soluble, and eight are essential human nutrients.

Today, each B vitamin has a name, not just a numeric designation like B1, B2, or B3. If you are interested in taking a supplement containing B vitamins, choose one containing the eight essential B vitamins, including thiamine (B1), riboflavin (B2), and pyridoxine (B6).

Vitamin B-3, another essential B vitamin, can be confusing because the same compound has four different common names: niacin, nicotinic acid, niacinamide, and nicotinamide. Other "essential" B vitamins include folacin, also known as folic acid, pantothenic acid, and biotin, which was once called vitamin H.

Although biotin deficiency is rare, taking a supplement containing biotin may help reduce hair loss if you are deficient in biotin. The recommended amount of biotin is 30 mcg daily. Unfortunately, some hair loss supplements contain very high doses of biotin, up to 5,000 mcg per serving. High levels of biotin can interfere with the accuracy of thyroid function tests. You can end up taking too much or too little thyroid supplement medication.

5 key facts about B-complex vitamins:

1. There are no standardized B-Complex formulas.

All B vitamins come from the original B vitamin compound. A supplement containing more than one B vitamin can be labeled as B-complex. There’s no consistency in which individual B vitamins are included in B-Complex supplements.

2. There are 8 essential B vitamins.

Of the 11 different individual B vitamins identified, 8 are considered essential in humans. B-Complex vitamins usually contain three to eight of these.

3. B vitamins have multiple names.

Although many B vitamins are identified by the letter B followed by a number, each of the B vitamins also has its own name.

4. All B vitamins are water-soluble and eliminated in urine.

Any excess B vitamin will be eliminated by your kidneys into your urine. Riboflavin (vitamin B-2) is responsible for the characteristic bright yellow urine experienced by many people who take B vitamins.

5. If you take a thyroid supplement, beware of high doses of biotin.

Hair, Skin, and Nails supplement formulas often contain very high amounts of biotin, which can interfere with the accuracy of thyroid blood testing.

Dr. Louise Achey, Doctor of Pharmacy, is a 44-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog, TheMedicationInsider.com.   Ó2023 Louise Achey