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Reply to JE Baggott

Jean Mayer USDA Human Nutrition Research, Center on Aging, Tufts University, 711 Washington Street, Boston, MA 02111, E-mail: paul{at}hnrc.tufts.edu
Division of Health Examination Statistics, National Center for Health Statistics, Centers for Disease Control and Prevention, 6525 Belcrest Road, Room 1000, Hyattsville, MD 20782

Dear Sir:

Baggott suggests that the data presented in 2 recent papers in the Journal (1, 2) conflict with the well-established inverse relation between circulating total homocysteine and folate concentrations (3–5). The basis of his assertion is the fact that Mexican American females in the third National Health and Nutrition Examination Survey (NHANES III) had on average lower serum total homocysteine concentrations (1) and lower serum folate concentrations than non-Hispanic white females (2). However, Baggott's statement that "The trend for lower mean serum folate concentrations is apparently associated with the lower mean serum homocysteine concentrations" is incorrect. In more recent analyses, higher serum folate concentrations were a strong predictor of lower total homocysteine concentrations in the NHANES III sample and this relation was not affected by race or ethnicity (6). When the relation between the logarithm of serum total homocysteine and the logarithm of serum folate was examined separately for Mexican American females, homocysteine concentrations were observed to be 16% lower with each doubling of serum folate concentrations (P < 0.001). Moreover, the difference in homocysteine concentration between Mexican American and non-Hispanic white females was independent of serum folate or vitamin B-12 concentrations. After adjustment for these vitamins as well as age and serum creatinine concentrations, the geometric mean total homocysteine concentration was 6% lower for Mexican American females than for non-Hispanic white females in the NHANES III sample, a small but significant difference (P < 0.01).

We have not yet identified the reason for the lower total homocysteine concentration in Mexican American females, but many factors other than folate and vitamin B-12 concentrations influence homocysteine concentrations. The large differences in homocysteine concentrations between males and females and young and old persons are not explained by circulating concentrations of folate or vitamin B-12 (6). Lifestyle factors and racial and genetic differences influence circulating total homocysteine concentrations (7–10). Until the basis for the lower homocysteine concentrations in Mexican American females is examined, we only know for certain that the lower total homocysteine concentration in this population is not the result of higher serum folate and vitamin B-12 concentrations.

REFERENCES

1. Jacques PF, Rosenberg IH, Rogers G, et al. Serum total homocysteine concentrations in adolescent and adult Americans: results from the third National Health and Nutrition Examination Survey. Am J Clin Nutr 1999;69:482–9.[Abstract/Free Full Text]
2. Ford ES, Bowman BA. Serum and red blood cell folate concentrations, race, and education: findings from the third National Health and Nutrition Examination Survey. Am J Clin Nutr 1999;69:476–81.[Abstract/Free Full Text]
3. Selhub J, Jacques PF, Wilson PWF, Rush D, Rosenberg IH. Vitamin status and intake as primary determinants of homocysteinemia in the elderly. JAMA 1993;270:2693–8.[Abstract/Free Full Text]
4. Refsum H, Ueland PM, Nygård O, Vollset SE. Homocysteine and cardiovascular disease. Annu Rev Med 1998;49:31–62.[Medline]
5. Boushey CJ, Beresford SM, Omen GS, Motulsky AG. A quantitative assessment of plasma homocysteine as a risk factor for vascular disease: probable benefits of increasing folic acid intakes. JAMA 1995; 274:1049–57.[Abstract/Free Full Text]
6. Selhub J, Jacques PF, Rosenberg IH, et al. Serum total homocysteine concentrations in the third National Health and Nutrition Examination Survey (1991–1994): population reference ranges and contribution of vitamin status to high serum concentrations. Ann Intern Med 1991;131:331–9
7. Nygård O, Refsum H, Ueland PM, Vollset SE. Major lifestyle determinants of plasma total homocysteine distribution: the Hordaland Homocysteine Study. Am J Clin Nutr 1998;67:263–70.[Abstract]
8. Ubbink JB, Vermaak WJ, Delport R, van der Merwe A, Becker PJ, Potgieter H. Effective homocysteine metabolism may protect South African blacks against coronary heart disease. Am J Clin Nutr 1995;62:802–8.[Abstract/Free Full Text]
9. Ubbink JB, Christianson A, Bester MJ, et al. Folate status, homocysteine metabolism, and methylene tetrahydrofolate reductase genotype in rural South African blacks with a history of pregnancy complicated by neural tube defects. Metabolism 1999;48:269–74.[Medline]
10. Arruda VR, Siqueira LH, Goncalves MS, et al. Prevalence of the mutation C677T in the methylene tetrahydrofolate reductase gene among distinct ethnic groups in Brazil. Am J Med Genet 1998; 78:332–5.[Medline]

This Article Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jacques, P. F Articles by Johnson, C. L Search for Related Content PubMed Articles by Jacques, P. F Articles by Johnson, C. L Agricola Articles by Jacques, P. F Articles by Johnson, C. L