Elderly people often develop vitamin B12 deficiencies as the effects of ageing impact the body's ability to absorb nutrients from food. Yet the vitamin has been shown to reduce levels of the amino acid homocysteine, high levels of which are linked to increase risk of heart disease and Alzheimer's.
Traditional treatment for this vitamin deficiency is through injections of cobalamin but taking supplements is a painless and therefore, preferable method.
Yet when a team led by Dr Lisette de Groot of Wageningen University in the Netherlands investigated the doses of cyanocobalamin supplements needed to correct this deficiency, they found that only daily doses of at least 647 mug of cyanocobalamin could reduce the deficiency by 80-90 per cent.
Their study tested different daily doses of vitamin B12 supplements in 120 people over the age of 70.
"The lowest dose of oral cyanocobalamin required to normalize mild vitamin B12 deficiency is more than 200 times greater than the recommended dietary allowance, which is approximately 3 mug daily," the authors write in the 23 May issue of the Archives of Internal Medicine.
Neither the US nor the European authorities have set upper safe levels for B12 supplements but an expert group commissioned by the UK recently proposed that 2000mcg be recommended as the upper safe level for this vitamin.
Changing RDAs to the maximum level tested in this study would therefore be within guidance safety levels.