As the labeling on many B vitamins will inform you, they are more “complex” than the other vitamins. That’s because each of the others — A, C, D, E and (the alphabetically disordered) K — is chemically the same thing. But it was later discovered that what scientists thought was vitamin B was actually multiple different vitamins, and because the nearby letters of the alphabet were claimed, the different versions of vitamin B were given subscripts and individual names. Here’s a rundown on a few of the more critical Bs.

B-1 (Thiamine): Nerves and muscles depend on this vitamin for proper function, making it an important supplement for those who weight-train.

B-2 (Riboflavin): B-2 helps support energy metabolism at the cellular level. Having plenty of riboflavin helps your cells effectively use the protein, carbs and fats you consume as energy rather than storing them as fat.

B-3 (Niacin): Because improved circulation is one of niacin’s benefits, it is often included in workout supplements. It’s also involved in energy metabolism.

B-6 (Pyridoxine): Known better by its number than its name, B-6 is involved in converting abundant amino acids into those in which the body is deficient. B-6 also plays an important role in hemoglobin synthesis, and it helps regulate blood glucose, support immune function and increase hormone activity.

B-12 (Cobalamin): As with B-6, this B vitamin is most often called “B-12.” It supports the production of red blood cells, helps protect nerves and build bones, and regulates DNA synthesis.

We recommend taking two doses per day of a B-complex supplement that provides 100 milligrams of B-1, B-2, B-3 and B-6 and at least 100 micrograms of B-12.