Tuesday, July 7, 2009
The B vitamins are eight water-soluble vitamins that play important roles in cell metabolism. Historically, the B vitamins were once thought to be a single vitamin, referred to as vitamin B (much like how people refer to vitamin C or vitamin D). Later research showed that they are chemically distinct vitamins that often coexist in the same foods. Supplements containing all eight are generally referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific name of each vitamin (e.g. B1, B2, B3 etc ).
The B vitamins often work together to deliver a number of health benefits to the body. B vitamins have been shown to:
- Support and increase the rate of metabolism
- Maintain healthy skin and muscle tone
- Enhance immune and nervous system function
- Promote cell growth and division — including that of the red blood cells that help prevent anemia.
- Reduce the risk of pancreatic cancer, one of the most lethal forms of cancer, when consumed in food, but not when ingested in vitamin tablet form.
Together, they also help combat the symptoms and causes of stress, depression, and cardiovascular disease.
All B vitamins are water soluble, and are dispersed throughout the body. Most of the B vitamins must be replenished daily, since any excess is excreted in the urine.
Different B vitamins come from different natural sources, such as potatoes, bananas, lentils, chile peppers, tempeh, liver oil, liver, turkey, tuna, nutritional yeast (or brewer's yeast) and molasses. Marmite and Vegemite bill themselves as "one of the world's richest known sources of vitamin B". As might be expected, due to its high content of brewer's yeast, beer is a source of B vitamins, although this may be less true for filtered beers and the alcohol in beer impairs the body's ability to activate vitamins.
The B-12 vitamin is of note because it is not available from plant products, making B-12 deficiency a concern for vegans. Manufacturers of plant-based foods will sometimes report B-12 content, leading to confusion about what sources yield B-12. The confusion arises because the standard US Pharmacopeia (USP) method for measuring the B-12 content does not measure the B-12 directly. Instead, it measures a bacterial response to the food. Chemical variants of the B-12 vitamin found in plant sources are active for bacteria, but cannot be used by the human body. This same phenomenon can cause significant over-reporting of B-12 content in other types of foods as well.
Vitamin B may also be delivered by injection to reverse deficiencies.