Vitamin B12

Vitamin B12- rich meals (covers at least 1 day B12):

1. Zucchini spaghetti with prawn, serves 4 people
2. Matcha rice with salmon and vegetables, serves 4 people

Scientific studies (review articles) on the relationship between vitamin B12 and disease prevention:
A review article (a collection of scientific studies on a specific topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:
"Do taking dietary supplements make sense?" Yes for a positive conclusion and no for a negative conclusion.

A review article (a collection of scientific studies on a specific topic) of cohort studies or case-control studies will answer the following question:
"Should I change my diet?".

1. Peripheral neuropathy is associated with lowered plasma vitamin B12 levels
2. Oral vitamin B supplementation does not prevent cognitive decline in cognitively unimpaired individuals
3. Vitamin B12, D and E reduce eczema
4. Low folate levels increase risk of depression among the aged people
5. Postherpetic neuralgia patients benefit from vitamin B12 supplementation
6. 1 μg/day dietary B12 intake increases esophageal cancer
7. Reduced serum levels of folate and vitamin B12 increase peripheral neuropathy risk among patients with type 2 diabetes
8. Maternal vitamin B12 deficiency increases low birth weight in newborns

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

• Vitamin B12 (cobalamin, Cbl) is a water-soluble vitamin.
  Vitamin B12 is the generic name for a specific group of cobalt-containing corrinoids with biological activity in humans.
• In foods, hydroxo-, methyl- and 5'-deoxyadenosyl-cobalamins are the main cobalamins present.
• Plant foods does not contain vitamin B12.
• Vitamin B12 only occurs in foods of animal origin, likes meat, liver, kidney, yogurt, dairy products, fish, clams, oysters, nonfat dry milk, salmon and sardines.
• The two forms of vitamin B12 having activity in B12-dependent enzymes within the human body are adenosylcobalamin (AdeCbl) and methylcobalamin (MetCbl).
• Vitamin B12 is needed for building proteins in the body, red blood cells and normal function of nervous tissue.
• B12-dependent enzymes play an important role in the folate-dependent methylation of homocysteine to methionine and in the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A.
• The estimated daily requirements of vitamin B12 are 2-5 mcg (μg).
• A dietary vitamin B12 deficiency can occur in strict vegetarians or after gastrectomy, and other diseases affecting cobalamin absorption.
• Dietary deficiency is rare in younger people living in the community but occurs more frequently in older people, particularly those living in institutional environments.
• Vitamin B12 deficiency can lead to moderate hyperhomocysteinaemia (plasma homocysteine concentrations > 12 μmol/L), a possible risk factor for occlusive vascular disease.
• Pernicious anemia (PA) is a macrocytic anemia that is caused by vitamin B12 deficiency, as a result of intrinsic factor deficiency.
• Causes of the deficiency include, most frequently, foodcobalamin malabsorption syndrome (> 60% of all cases), pernicious anemia (15%–20% of all cases), insufficent dietary intake and malabsorption.
• Dietary vitamin B12 is absorbed through the Intrinsic Factor (IF) – a glycoprotein secreted by the parietal cells of the stomach – in the ileum of the small intestine.
  The IF-cobalamin complex is saturated with dosages between approximately 1.5 and 4 μg of vitamin B12 per meal.
  At intakes around 1 μg about 50% is absorbed, at dosages around 25 μg only 5% is absorbed.
  Very small amounts (ca 1-1.2%) can be absorbed by passive diffusion, in the absence of intrinsic factor.
• In the absence of the intrinsic factor vitamin B12 injections should be given to treat a deficiency.
• The total body pool size is estimated between 1-10 mg or sufficient for 3-5 years. The liver is the predominant storage site for vitamin B12.
• Cyanocobalamin and hydroxycobalamin are the most commonly encountered supplemental forms of vitamin B12.
• The upper tolerable level (UL) for vitamin B12 has not been set yet.