Vitamin B12.(Section 2: Key nutrients delivered by red meat in the diet)

KEY POINTS

* Subclinical vitamin B12 deficiency (low serum vitamin B12, and/or raised methylmalonate) occurs in 10% or more of older people, in Australia and other developed countries. Causes include inadequate liberation of vitamin B12 from its natural binding to the protein in foods because of poor gastric acid production. There is evidence that in some cases, the diet has been inadequate in animal foods. At present, it is not clear whether these low biochemical values lead to any serious consequences.

* The recent recommended dietary allowance reports for vitamin B12 in the USA and Canada recommend that older people should obtain most of their vitamin B12 from fortified foods or from supplements of free (crystalline) vitamin B12. In Australia and New Zealand, advice in the Nutrient Reference Values report is that older people with low stomach acid secretion 'May require higher intakes of vitamin B12 rich foods "(e.g. meat)" vitamin B12 fortified foods "(not generally available here)" or supplements'.

* Dietary deficiency of vitamin B12 occurs in strict vegans. It is usually subclinical. But very severe clinical deficiency has been reported in infants breastfed by a vegan mother.

* Now that folate intakes have been increased by fortification of foods--mandatory in North America, at present voluntary in Australia and New Zealand--some experts and some evidence warn that it may be advisable for people to increase B12 intake.

* Meat and meat products are the major source of vitamin B12 in Britain. Presumably this would be similar in Australia. Liver and kidney are the foods richest in this vitamin.

INTRODUCTION