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Food Science and Human Nutrition, Iowa State University, Ames, IA 50011-1123
* To whom correspondence should be addressed. E-mail: shendric{at}iastate.edu.
Apparent absorption of isoflavones varies greatly among individuals but is relatively stable within an individual. We hypothesized that high urinary isoflavone excreters would show less plasma non-HDL cholesterol (non-HDL-C) than low isoflavone excreters after soy protein feeding. Fifty Golden Syrian hamsters were fed a high-fat/casein diet (n = 10) or a high-fat/soy protein diet (n = 40) for 4 wk. We identified 2 distinct urinary isoflavone excretion phenotypes based upon HPLC analysis of urinary glycitein using a pairwise correlation plots analysis, or based upon total urinary isoflavone using a hierarchical cluster test. High isoflavone excreters showed greater urinary isoflavones (P < 0.05) than did low isoflavone excreters at wk 1 and 4. The low urinary glycitein excretion phenotype was more stable than the high urinary glycitein excretion phenotype by McNemar's test. High urinary isoflavone excreters had significantly less non-HDL-C than did the low isoflavone excreters or casein-fed controls (P < 0.05). Plasma total and non-HDL-C were negatively correlated with urinary daidzein, glycitein, and total isoflavone excretion (r = 0.45 to 0.58, P < 0.05). Urinary isoflavone excretion phenotypes predicted the cholesterol-lowering efficacy of soy protein. Isoflavone absorbability, probably due to gut microbial ecology, is an important controllable variable in studies of effects of soy protein on blood lipids.