Micronutrients- B12

Ways B-12 Absorption can be disrupted

Absence or defective R-protein, pancreatic proteases or intrinsic factor Defective binding of the intrinsic factor/B-12 complex Absence or surgical removal of much of the ileum and stomach Disease in the ileum like Crohn's disease Bacterial overgrowth in the small intestine Tapeworm infestation Use of certain anti-reflux meds Use of metformin to lower blood sugar Chronic malabsorption syndromes that may occur with various gastrointestinal disorders

Absorption

Absorption of B-12 is quite complex In food B-12 is bound to protein HCL and pepsin in gastric juice release vitamin B-12 from these proteins In the stomach the free vitamin B-12 binds to R-protein, which originates in the salivary glands The free vitamin B-12 combines with intrinsic factor a protein like compound produced by parietal cells in the stomach that enhances Vit B-12 absorption In the small intestine pancreatic protease enzymes release vitamin B-12 from R-protein/vitamin B-12 complex Vitamin B-12 intrinsic factor complex travels to ileum, where vitamin B-12 is absorbed and transferred to the blood transport protein transcobalamin II This complex enters the portal vein and is delivered to the liver

Storage of B-12

B-12 is continually secreted into the bile, but most of it is reabsorbed Little B-12 is excreted in the urine, what is not used is reabsorbed Normally healthy adults absorb about 50% of the B-12 in foods The liver can store enough vitamin B-12 to last several years.

Functions of Vitamin B-12

Coenzymes that move 1-C groups Citric acid cycle Oxidation of fatty acids Folate metabolism Nervous system functions - maintenance of myelin sheath

Two forms of supplemental B-12

Cyanocobalamin Methylcobalamin

B 12 in Foods

Plants do not synthesize vitamin B-12 All vitamin B-12 compounds are synthesized exclusively by microorganisms, mainly bacteria Animals acquire vitamin B-12 from ingesting soil while they graze Ruminant animals also synthesize vitamin B-12 from bacteria in the multiple compartments of their stomachs

Deficiency in infancy

infancy can lead to diminished brain growth, poor intellectual development and degeneration of the spinal cord

Can B-12 be supplemented via oral dose? (5 hour energy)

it needs to be bound to something to be absorbed so more than likely you are not absorbing it

Vitamin B-12 Needs and Upper Level

RDA of vitamin B-12 for adults is 2.4 ug/day Daily value on food and supplement labels is 6 ug Average adult man consumes 3 times the RDA and women 2 times the RDA This high intake provides the average meat-eating person with 2-3 years storage of vit. B-12 in the liver There is no upper limit, no adverse effects observed from excess intakes of B-12

Food sources of B12

Vitamin B-12 sources for humans are of animal origin (meat, poultry, seafood, eggs, and dairy) Especially rich sources are liver, kidney, heart and fortified foods like ready to eat cereals Foods like tempeh and miso contain vitamin B-12 analogs, but this type of B-12 cannot be used by the body

B-12 Deficiencies

20% of older adults have poor B-12 status Due to impaired absorption due to atrophic gastritis Does not cause anemia but may cause neurological problems and elevated blood homocysteine Consumption of crystalline vitamin B-12 in foods or as a supplement can improve status! Two forms of supplemental B-12: Cyanocobalamin Methylcobalamin

Dx with an impaired absorption of B-12

3 options 1)B-12 nasal gel 2)B-12 shot 3)Very high oral doses of 1-2 mg daily. A very small amount can be absorbed by passive diffusion and does not require the intrinsic factor system

Diseases

Looks like folate deficiency Causes Usually due to decreased ability for absorption Consequences Pernicious anemia Nerve degeneration, weakness Tingling/numbness in the extremities (parasthesia) Paralysis and death

Treatment

Monthly injections Nasal gel Weekly ingestion of megadoses

Susceptible populations

Older adults Infants of vegan mothers Vegans (after many years) People with malabsorptive diseases

Uniqueness

One way- foods of animal origin are the only reliable sources of B-12 Second way- it is the only vitamin that contains a mineral cobalt as part of its structure The discovery of B-12 and how it prevents pernicious anemia was so significant between the years of 1934-1965 researchers were awarded 6 Nobel Prizes during this time period

Consequences or signs of a B-12 deficiency?

Tingling of fingers and toes, pernicious anemia, nerve degeneration, weakness, paralysis, death

Vegans breastfeeding

Vegans that choose to breastfeed their infants need to be aware their breast milk may deficient in B-12