To the Editor: In their study of phytoestrogens and risk of lung cancer, Dr Schabath and colleagues1 report on the intake of lignans in a US population. Their results, while interesting, are discrepant with those of other studies.
In their article, the total intake of lignans was calculated as the sum of the plant lignans secoisolariciresinol and matairesinol and the mammalian enterolignans enterodiol and enterolactone. Enterolignans are not present in foods but can be determined via in vitro fermentation. Enterolignans are formed by bacteria in the colon at the expense of plant lignans. Summing plant lignans and enterolignans counts food contribution to the lignan intake twice. As a result, the estimates of total lignan intakes and the odds ratios based on these (in Tables 2, 4, and 6) may be biased.