Vitamin C sometimes indicated to lower homocysteine

As a practicing clinician (or knowledgeable layperson) have you encountered patients who continue to have higher plasma homocysteine levels than you'd like despite objective laboratory evidence (such as the relevant organic acids) that they are replete for vitamin B12, folic acid and vitamin B6? (I have.) A paper just published in the Annals of Nutrition & Metabolism throws some welcome light on the matter. The authors state:

"The factors influencing total plasma homocysteine levels (tHcy) are of special interest in the attempt to reduce cardiovascular risk...This investigation aimed to assess the independent effects of antioxidant vitamins on tHcy in elderly people."

The authors examined 184 subjects in an aging population in Giessen (GISELA), Germany for the effects of plasma levels, intake and supplementation of vitamin C, vitamin E, and β-carotene on tHcy. What did their data show?

"Serum folate, the estimated glomerular filtration rate (eGFR), and plasma vitamin C showed a negative association with tHcy in simple regression analysis. In a subsequent multiple regression analysis, eGFR, serum folate, and plasma vitamin C were the relevant independent predictors of tHcy."

In other words, higher plasma vitamin C was associated with lower homocysteine (along with the already recognized folic acid and eGFR as a metric for kidney function). There is good evidence for the importance of homocysteine in brain as well as cardiovascular health. The authors' conclusion can be brought to mind when homocysteine levels fail to reach optimum despite the well-known interventions:

"Vitamin C may be an independent predictor of tHcy in free-living elderly people and, therefore, should be considered in attempts to reduce tHcy."

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