Expert Nutrition

Vitamin B12 (Cobalamin)

Vitamin B12 also commonly known as cobalamin has a similar role to folic acid. It is needed to make red blood cells, DNA, the genetic material of cells and myelin, a sheath that surrounds nerve fibres. Vitamin B12 also assists in the activation of folate where a deficiency in vitamin B12 can manifest in a similar way to that of a folate deficiency.

Unlike most other water soluble vitamins, vitamin B12 is stored in substantial amounts, mainly in the liver. It is estimated that can take up to 5 years to exhaust these stores and therefore vitamin B12 deficiency symptoms due to depletion may take many years to develop.

Deficiency in vitamin B12 can result from a very strict vegetarian diet although is more likely to come about through a problem in the small intestine that leads to the malabsorption of the vitamin. Pernicious anaemia is one of the main concerns that develop as a result of a vitamin B12 deficiency, however nerve problems and weakness are also common.

Vitamin B12 is found in most animal products including liver, eggs, dairy, poultry, fish and red meat. Although the recommended daily intake of vitamin B12 is only small there has been very low toxicity reported in doses up to 1000 times the recommended dose.

Although a healthy diet that includes meat, fish and a wide variety of plant based foods is believed to be adequate to prevent vitamin B12 deficiency in healthy individuals, supplements that contain vitamin B12 along with folate and vitamin B6 have been proven to be the most effective in lowering blood levels of homocysteine, which is a powerful oxidising agent that is associated with an increased risk of heart disease. It is the belief of many nutritional supplement companies that by taking such a supplement we can reduce homocysteine levels and therefore reduce the risk of developing chronic diseases such as heart disease. More information on this topic can be found in the chapter that discusses nutritional supplements.

Additional possible benefits of vitamin B122

  • May protect against heart disease and nerve damage
  • May protect against neural tube defects in foetuses during the first 6 weeks of pregnancy

Recommended Dietary Intake for Vitamin B12

A recent re-evaluation of dietary requirements for all vitamins and minerals was published by the National Health and Medical Research Council for Australia and New Zealand6. The dietary recommendations for Vitamin B12 from this publication are summarised below

Please refer to the following definitions when interpreting these recommendations:

RDI-Recommended Daily Intake
The average daily intake level that is sufficient to meet the nutritional requirements of nearly all (97-98%) health individuals in a particular life stage and gender group.

AI-Adequate Intake (used when an RDI cannot be determined)
The average daily nutrient intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate.

UL-Upper Limit of Intake
The highest average daily nutrient intake level likely to pose no adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects increases.

RECOMMENDATIONS BY LIFE STAGE AND GENDER - Vitamin B12

InfantsAI
0-6 months0.4 µg/day
7-12 months 0.5 µg/day

Children and AdolescentsRDI
All
1-3 years 0.9 µg/day
4-8 years 1.2 µg/day

Boys
9-13 years 1.8 µg/day
14-18 years 2.4 µg/day

Girls
9-13 years 1.8 µg/day
14-18 years 2.4 µg/day

AdultsRDI
Men
19-30 years 2.4 µg/day
31-50 years 2.4 µg/day
51-70 years 2.4 µg/day
>70 years 2.4 µg/day

Women
19-30 years 2.4 µg/day
31-50 years 2.4 µg/day
51-70 years 2.4 µg/day
>70 years 2.4 µg/day

Pregnancy
14-18 years 2.6 µg/day
19-30 years 2.6 µg/day
31-50 years 2.6 µg/day

Lactation
14-18 years 2.8 µg/day
19-30 years 2.8 µg/day
31-50 years 2.8 µg/day

The safe upper level of intake for vitamin B12 cannot be estimated as there are no adverse events that have been associated with vitamin B12 consumption as food or through supplements.

Source: National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand. Department of Health and Ageing, Canberra 2006, copyright Commonwealth of Australia reproduced by permission.

Vitamin B12 back to Vitamins


References:
1. Stanton R. Foods that harm, foods that heal: An A-Z guide to safe and healthy eating. Readers Digest; 2006, pp378-382.
2. Wahlqvist, M.L., et al. Australia and New Zealand: Food and Nutrition. 2nd Ed. Allen and Unwin, Sydney; 2002, 258-260.
3. The Merck Manual of Medical Information 2nd Ed. Beers, M.H., Fletcher, A. J., Jones T. J., Porter, R., Berkwits, M., et al., editors. Pocket Books Reference; 2003 pp 816.
4. Mann, J., Truswell, S. Essentials of Human Nutrition. Oxford Medical Publications, New York. 2000 pp 213-216.
5. MacWilliam, L.D. Comparative Guide to Nutritional Supplements. Northern Dimensions Publishing; 2005 pp 36-37.
6. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand. Department of Health and Ageing, Canberra 2006 pp 91-96. Copyright Commonwealth of Australia reproduced by permission.


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