From the Guidelines
Yes, plasma homocysteine is elevated in the context of Vitamin B12 (cobalamin) deficiency.
Key Points
- Hyperhomocysteinemia is caused by nutritional deficiencies of pyridoxine (vitamin B6), folic acid, and cobalamin (vitamin B12) 1.
- Vitamin B12 plays a crucial role in the remethylation pathway of homocysteine metabolism, and its deficiency can lead to elevated plasma homocysteine levels 1.
- Studies have shown that supplementation with folic acid, vitamin B12, and/or vitamin B6 can lower plasma homocysteine levels in the general population 1.
- In dialysis patients, routine vitamin supplementation, including vitamin B12, is necessary to replace losses from dialysis and prevent elevation in serum homocysteine levels 1.
Evidence Summary
The evidence suggests that vitamin B12 deficiency is a cause of hyperhomocysteinemia, and supplementation with vitamin B12 can help lower plasma homocysteine levels. The relationship between homocysteine levels and cardiovascular disease is well established, with elevated homocysteine levels associated with a 2- to 3-fold increased risk for atherosclerotic vascular disease, including stroke 1.
Clinical Implications
- Vitamin B12 deficiency should be considered as a potential cause of hyperhomocysteinemia.
- Supplementation with vitamin B12, along with folic acid and vitamin B6, may be necessary to lower plasma homocysteine levels and reduce the risk of cardiovascular disease.
- Routine vitamin supplementation, including vitamin B12, is essential for dialysis patients to prevent elevation in serum homocysteine levels and maintain adequate nutritional status 1.
From the Research
Plasma Homocysteine Levels in Vitamin B12 Deficiency
- Plasma homocysteine levels are elevated in the context of Vitamin B12 (cobalamin) deficiency, as evidenced by multiple studies 2, 3, 4, 5, 6.
- The presence of vitamin B12 is essential in homocysteine metabolism, and deficiency of this nutrient is associated with various degrees of hyperhomocysteinemia 2.
- Elevated plasma levels of homocysteine can be caused by deficiency of either vitamin B12 or folate, leading to hyperhomocysteinemia (HHcy) 3.
- Studies have shown that vitamin B12-deficient subjects have higher total plasma homocysteine levels compared to controls and heterozygotes for homocystinuria due to cystathionine beta-synthase deficiency 6.
- Administration of hydroxycobalamin to vitamin B12-deficient subjects has been shown to decrease homocysteine levels to normal, highlighting the importance of vitamin B12 in homocysteine metabolism 6.
Relationship Between Homocysteine and Vitamin B12 Deficiency
- Hyperhomocysteinemia is associated with several human disorders, including cardiovascular disease, neurodegenerative disorders, pregnancy complications, and fractures 2, 3.
- Vitamin B12 deficiency can lead to hemolytic anemia and severely elevated homocysteine levels, which can be resolved with vitamin B12 treatment 4.
- Elevated plasma homocysteine concentration, but not a low serum vitamin B12 concentration, increases the risk of cardiovascular morbidity and mortality in patients with ischemic heart disease 5.
- The measurement of homocysteine levels may be helpful for identifying subjects at greater risk of disease, who may benefit from a more aggressive treatment of other modifiable risk factors 2, 3.