Understanding the B Complex

The water-soluble B vitamins are collectively referred to as B complex. They include thiamin (B1), riboflavin (B2), niacin or niacinamide (B3), pyridoxine (B6), folic acid, vitamin B12, biotin and pantothenic acid (B5). In addition, choline, inositol and PABA (para-aminobenzoic acid) are compounds that are not technically B vitamins, but which have related functions and so are often included with B complex products. Each of the B vitamins has its own functions to serve in the body; but, in general, they play a role in energy metabolism and promote homeostasis when the body is under stress. The use of the entire B complex is recommended, since the individual B vitamins affect one another’s absorption, metabolism and excretion.¹  

Energizing Vitamin

Each of the B vitamins is converted into coenzymes in the body. These B vitamin coenzymes are involved, directly or indirectly, in energy metabolism. Some facilitate the energy-releasing reactions themselves within the mitochondria; others help build new cells to deliver the oxygen and nutrients that permit the energy pathways to run. Research shows thiamin is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle; riboflavin is required for the flavoenzymes of the respiratory chain; NADH is synthesized from niacin and is required to supply protons for oxidative phosphorylation; pantothenic acid is required for coenzyme A formation, and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation; and biotin is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation.² Folic acid and choline are believed to be central methyl donors required for mitochondrial protein and nucleic acid synthesis through their active forms.³

Active individuals with poor or marginal nutritional status for a B vitamin may have decreased ability to perform exercise at high intensity. Exercise stresses metabolic pathways that depend on thiamine, riboflavin and B6. Consequently, the requirements for these vitamins may be increased in athletes and active individuals.⁴ In fact, exercise could increase the need for these micronutrients in several ways: through decreased absorption of the nutrients; by increased turnover, metabolism or loss of the nutrients; through biochemical adaptation as a result of training that increases nutrient needs; by an increase in mitochondrial enzymes that require the nutrients; or through an increased need for the nutrients for tissue maintenance and repair. Other research suggests exercise may increase the requirements for riboflavin and vitamin B6, and possibly for folic acid and vitamin B12.⁵ Biochemical evidence of deficiencies in some of these vitamins in active individuals has been reported, including riboflavin and B6.⁶ Exercise appears to decrease nutrient status even further in active individuals with preexisting marginal vitamin intakes or marginal body stores. Thus, active individuals who restrict their energy intake or make poor dietary choices are at greatest risk for poor B vitamin status, and should consider supplementing with B complex vitamins.