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To the Editor.—The conclusion of the article by Dr Rimm and colleagues1 and the Editorial by Dr McCully2 that intake of folate and vitamin B6above the current dietary content may be important in the primary prevention of coronary heart disease (CHD) in women is not warranted because the data do not prove that the association established is a causal one. For such proof, controlled trials with homocysteine-lowering therapy are required.
The data in the study by Rimm et al actually support a confounding variable rather than a causal factor. Lifestyles of the women in the lowest quintile were definitely unhealthy as estimated by the presence of hypertension, amount of exercise, and intake of fat, fiber, and alcohol. In contrast, women in the highest quintiles had healthy lifestyles to the extent of taking vitamin supplements.
Although some of the risk factors for CHD were adjusted in the analysis, others were not, such as cholesterol level and psychosocial lifestyle factors including life stress, job demand, depression, and exercise. Considering the major impact of unhealthy lifestyles on well-established risk factors for CHD, the difference in risk of CHD was probably not the consequence of levels of folate and vitamin B6intake but rather of difference in lifestyles.
Another argument in favor of confounding is that slightly or even moderately elevated homocysteine levels, as seen with heterozygous cystathionine synthetase deficiency, did not give rise to increased risk of CHD.3 Even the homozygous form of this disease, with more than 100-fold levels of homocysteine (although it commonly gave rise to severe peripheral vascular disease), gave rise to CHD in 10 of 629 patients (less than 2% of the cases).4 We believe that homocysteine is not as harmful for the heart as it may seem.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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