Hypothesis identification in article analysis

¶ … Chen, Ho, Lam, Ho, & Woo, 2003)

The article used for this research is a free full-text manuscript that may be found on PubMed.

The purpose of the present study was to investigate the effects of dietary intake of soy isoflavones on bone loss in postmenopausal women. Subjects were aged 48 to 62 years and within 10 years of natural menopause. Exclusion criteria for this study included any diseases or medications, including use of exogenous estrogens, corticosteroids, thiazine, or any medication known to effect bone mass. This trial was a double-blind, placebo-controlled, randomized study that examined two doses of isoflavones (40 mg and 80 mg daily) and placebo on bone mass maintenance in early postmenopausal women. The alternate hypothesis of this study was that dietary isoflavone supplementation would prevent bone mineral loss in early postmenopausal women.

Subjects in the three intervention arms of the study had similar demographic characteristics. Annualized rates of bone mineral density change were similar among the three treatment groups. However, annualized bone mineral content change at the hip and trochanter was greater in the 80-mg group compared to the 40-mg and placebo group. Stratified analyses revealed that this beneficial effect was only noted in subjects with a low initial bone mineral content value. This beneficial effect was not observed in subjects with bone mineral content values above the median as baseline. Multiple regression analyses confirmed the positive effects of soy isoflavones on bone mineral content. For each 10-mg increase in isoflavone supplementation per day, annualized bone mineral content increases of 0.18%, 0.30%, and 0.20% were observed at the total hip, trochanter, and intertrochanteric regions of interest. Bone mineral content and density at the lumbar vertebrae was unchanged at all levels of isoflavone supplementation.

Common side effects reported with dietary isoflavone supplementation included abdominal distention, constipation, breast disorders, and menses-like bleeding. However, the incidence of these events was not significantly greater than the incidence observed in the placebo group.

Overall, the hypothesis statement in the introduction was very vague and not indicative of the study results. First, the authors speculated that soy isoflavone supplementation would prevent bone loss in postmenopausal women. However, the supplementation strategy did not show benefit in bone mineral density, only bone mineral content. Second, stratified analyses showed that these effects were only observed in subjects who presented with bone mineral content values below the sample median. Thus, the authors' hypothesis was incorrect because only one of the two measured variables showed a benefit and this benefit was only observed in a subset of the total sample.