March 7, 1986

Dietary Intake, the First Law of Thermodynamics, and the Properties of Yoga-Reply

Author Affiliations

Harvard Medical School Brigham and Women's Hospital Boston
Buckingham, Va

JAMA. 1986;255(9):1136-1137. doi:10.1001/jama.1986.03370090058013

In Reply.—  Dr Mann raises some methodological issues regarding our study in which we found that ingestion of dairy products selectively raised plasma low-density lipoproteins (LDL) rather than high-density lipoproteins. Dr Mann misapplies the problems of comparing nonconcurrent groups to our study. The two groups of vegetarians in our study were surveyed six years apart (rather than 12 years apart, as Dr Mann states). Use of "historical controls" in case-control studies can be misleading since incidence of a disease of interest can drift over years. However, our work dealt with the biologic effects of ingestion of dairy fat. These effects were studied by examining a group of lactovegetarians and comparing the findings with those made six years earlier in a group of strict vegetarians. What variables might confound such a comparison since the methods were kept constant? We consider it unlikely that evolutionary changes could have occurred in six years