Abstract
The study aimed to assess the prevalence and rate of development of a low (below normal) serum B12 level in clinically well persons on a total vegetarian diet (TVD) with and without supplementation/fortification with B12.
Serum B12 and red cell mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were measured in participants on a TVD for 12–340 months. Ability to absorb B12 orally was tested. In addition, urinary methylmalonic acid/creatinine ratio (UMMMCr) was measured in a subgroup of 27.
In 47 of 78 adults the B12 level was below 200 pg ml-1, and the MCV was 94.2 ± 4.0. The other 31 adults had a B12 level of 200 or above, averaged 293 ± 85 pg ml-1 and an MCV of 92.6 ± 4.6. Eight children and 12 adults were on the same TVD, but were using B12-fortified soy milk instead of cow's milk. Their B12 level ranged from 255 to 690 (average 417 pg ml-1) with a mean MCV of 88.8 ± 3.5 fl. The serum B12 level of seven of 16 adults with a low serum B12 who chewed a 100 μg tablet of B12 once a week for 6 weeks increased by 150%, whereas the serum B12 level increased by only 12% in the nine who gulped down the tablets (with water). In 10 who changed from a lacto-ovo-vegetarian (LOV) diet to a TVD, the mean serum B12 level dropped 35% from 415 ± 187 to 268 ± 75 pg ml-1 (p < 0.005) 2 months after starting the TVD. Seven of 11 participants with a B12 below 200 pg ml-1 had an elevated UMMA/Cr ratio, whereas all 16 with serum B12 levels above 200 pg m1-1 were normal.
Serum B12 levels decreased noticeably within 2 months on a TVD. Sixty-one per cent of those on the TVD for 1 year or more had serum B12 levels below normal, but those on the TVD had a slightly greater average MCV and MCH than those using cow's milk or soy milk fortified with B12. Two-thirds of those with low serum B12 had increased urinary methyl-malonic acid levels. The serum B12 increased with oral supplementation only if the tablet could be readily dissolved.