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Milk and Vitamin B12

The only natural source of vitamin B₁₂ is food of animal origin. Foods rich in B₁₂ include dairy, fish, meat, poultry, eggs and shellfish. Inadequate intakes have been shown to be an important contributor to low vitamin B₁₂ serum concentrations. Recent studies show that the vitamin B₁₂ in meat, the major source of vitamin B₁₂ for most individuals, may be less available than the vitamin B₁₂ in dairy products¹. Nutritional B₁₂ deficiency can develop easily in strict vegetarians and those who follow macrobiotic diets since they typically avoid the foods that are rich in B₁₂.

There is little information on the prevalence of B₁₂ deficiency in Canada. But a recent Canadian cross-sectional study of 1,424 pregnant women in Newfoundland found that 43.6% of women were B₁₂ deficient or had marginal B₁₂ levels².

We know that specific nutrient deficiencies can cause low birth weight and spina bifida, so it is also possible to envisage nutrient deficiencies affecting brain development in infants causing adverse effects. Reports of B₁₂ deficient infants (several of strict vegetarian mothers) showed anemia, irritability, anorexia and failure to thrive, as well as marked developmental regression and poor brain growth^3,4. The age of onset of symptoms may be important, as may the duration of symptoms. Although the response to treatment in the short term is encouraging, complete neurologic recovery may never be complete³. In a review by Graham, only 2 of 6 reported cases had normal intellectual outcome at 9 - 11 years. Another study reporting on older children discovered that B₁₂ deficiency early in life, due to macrobiotic diet consumption to the age of 6 years, may not be overcome in adolescence following moderate consumption of B₁₂ after the age of 6 years⁵.Children on macrobiotic diets until the age of 6 with marginal vitamin B₁₂ status were not able to overcome cognitive problems, due to the deficiency, regardless of moderate B₁₂ intakes in later years⁶. In fact, previously ‘macrobiotic’ subjects with low or normal vitamin B₁₂ status scored significantly lower in intelligence tests measuring reasoning, capacity to solve complex problems, abstract thinking ability and ability to learn³. These studies demonstrate the potential long-term risk in cognitive function that can occur in children who persistently avoid animal products due to medical reasons, beliefs, poverty or eating habits during the formative years.

Vitamin B₁₂ deficiency is estimated to affect 10-15% of people over age 60⁷. Prevalence of B₁₂ deficiency increases with age, especially over 65, and is frequently associated with Alzheimer’s disease⁸. Neurologic complications are found in 75-90% of individuals with clinically apparent vitamin B₁₂ deficiency. While low serum cobalamin levels are often found in apparently normal older subjects, a major worry of leaving vitamin B₁₂ deficiency untreated is that it may lead to subtle deterioration in cognitive function⁷.

Cognitive syndromes such as dementia, hallucination, frank psychosis, paranoia, depression, violent behaviour and changes in personality are not frequent, but vitamin B₁₂ deficiency should be considered as a possible cause of these symptoms⁹. In fact vitamin B₁₂ assay is part of the routine investigation of dementia in the United Kingdom. A study by Eastley et al¹⁰ of 1,432 patients found a positive treatment effect of B₁₂ among patients presenting with cognitive impairment. However, in the same study none of the B₁₂ deficiency-related-dementia was reversed with the treatment of B₁₂.

Keywords: B12

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  The contribution of milk products (milk, yogurt and cheese) to the daily nutrient intake of Canadians is divided as follows.¹

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