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Serum vitamin B 12 is a medical laboratory test that measure vitamin B 12 only in the blood binding to both transcobalamins. [1] Most of the time, 80–94% of vitamin B 12 in the blood binds to haptocorrin , while only 6–20% is binds to transcobalamin ll. [ 2 ] Only transcobalamin ll is "active" and can be used by the body. [ 1 ]
For this reason, elevated serum homocysteine over 15 micromol/L and methylmalonic acid (MMA) over 0.271 micromol/L are considered better indicators of B 12 deficiency, rather than relying only on the concentration of B 12 in blood. [2] However, elevated MMA is not conclusive, as it is seen in people with B 12 deficiency, but also in elderly ...
[56] [57] Low levels of serum vitamin B 12 may be caused by other factors than B 12 deficiency, such as folate deficiency, pregnancy, oral contraceptive use, haptocorrin deficiency, and myeloma. [57] High serum levels may caused by supplementing with vitamin B 12, present of antibodies to intrinsic factor, or due to underlying condition. [56]
Symptoms “A B12 deficiency can cause physical and neurological symptoms, and research is also growing to support that it can also cause psychological issues as well,” says Shapiro.
Evidence exists linking elevated homocysteine levels with vascular dementia [10] and Alzheimer's disease. [11] [12] [13] There is also evidence that elevated homocysteine levels and low levels of vitamin B6 and B12 are risk factors for mild cognitive impairment and dementia. [14]
Vitamin B12 does also accumulate in a few plant-based sources, including some mushrooms, seaweed, and nutritional yeast, but not enough to fortify vegans, who, in particular, should consider being ...
The resulting elevated concentrations of homocysteine and MMA are often found in patients with low serum vitamin B 12 and can usually be lowered with successful vitamin B 12 replacement therapy. However, elevated MMA and homocysteine concentrations may persist in patients with cobalamin concentrations between 200 and 350 pg/mL. [ 23 ]
Vitamin B 12 deficiency is preventable with supplements, which are recommended for pregnant vegetarians and vegans, and not harmful in others. [2] Risk of toxicity due to vitamin B 12 is low. [2] Vitamin B 12 deficiency in the US and the UK is estimated to occur in about 6 percent of those under the age of 60, and 20 percent of those over the ...