Hyperhomocysteinemia and cobalamin deficiency in young Asian Indians in the United States.

Hyperhomocysteinemia, a risk factor for vascular disease, may be a particular problem in Asian Indians, but information is limited, especially in the U.S., despite its growing Asian population. Moreover, suggestions have been made that folate deficiency is responsible for the hyperhomocysteinemia in Indians. Therefore, we studied homocysteine status in healthy Asian Indians in the U.S. prospectively, determined the frequency of cobalamin and folate deficiency as contributors to it, and examined whether food-cobalamin absorption contributed to cobalamin deficiency. Homocysteine levels were higher in Asian Indian men than in 4 other ethnic groups (P < 0.0001); 10/39 Indian men (25.6%) were hyperhomocysteinemic. Cobalamin levels were lower in Indian men (P = 0.000005) and women (P = 0.03) than in non-Indians; low levels were found more frequently in both Indian men (23/39; 59.0%) and women (5/21; 23.8%) than in others. Measuring methylmalonic acid in 10 selected subjects showed that the low cobalamin levels reflected cobalamin deficiency, and high methylmalonic acid levels were found in some subjects without hyperhomocysteinemia. Evidence of folate deficiency was not found in any subjects. Food-cobalamin absorption was normal in all 13 Indian subjects tested, including those with Helicobacter pylori infection. The results show that hyperhomocysteinemia is strikingly common in apparently healthy, young Asian Indian men. The cause appears to be cobalamin deficiency, which affected more than half of the Indian men, may be largely subclinical, is underestimated by homocysteine levels alone which were not always abnormal, and is probably largely dietary in origin. Folate deficiency is rare. This public health problem is amenable to prevention and treatment in this growing segment of the U.S. population. It was, parenthetically, noteworthy that many of the affected subjects were young physician trainees. Copyright 2002 Wiley-Liss, Inc.