One of the consequences of a vegetarian diet is an increased risk of vitamin B12 deficiency. This is because vitamin B12 is generally only found in foods of animal origin. Studies investigating the ingestion of diets devoid of animal product report an increased risk of haematological problems caused by a deficiency of vitamin B12. Algae is one food that may contain vitamin B12 but is not of animal origin, and is therefore often advocated to vegans as a dietary source. Researchers have investigated the effects of two algal products and fermented plant products on the haematological status of vitamin B12 deficient children. Eleven children ages 14 to 26 months received either plant based vitamin B12 sources, fish sources of vitamin B12, or a vitamin B12 supplement. Blood samples were then taken to assess the vitamin B12 status of the plasma and evaluate mean corpuscular volume (MCV).
The results showed that in the plant based group, intakes of vitamin B12 ranged from 0.1 to 2.7µg/d with the main sources being nori (porphyra tenera) and spirulina (Spirulina). In the fish group the intake of vitamin B12 was 0.2 to 2.0µg/d mainly from fish and dairy. Plasma vitamin B12 levels increased in 4 of the 5 fish eating children and the elevated MCV in these children declined to levels close to the reference range. However, in the plant eating group, plasma vitamin B12 levels increased in 3 of the 5 children, but the MCV values further deteriorated. Despite the small number of children in the study, there was a statistical significance between the fish and plant group in terms of MCV changes. The child given the vitamin B12 supplement at a dose of 125 µg/d, improved dramatically. This study suggests that plant sources of vitamin B12 may not be bioavailable.
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