Research Program, M.D. Van Loan

My most recent research has focused on 1) the role of phyto-estrogens, specifically soy isoflavones, in reducing post menopausal bone loss and 2) the effect of different diets and eating patterns on body composition, weight and fat loss, and bone metabolism.

Biography

     A native of West Springfield, Massachusetts, Dr. Van Loan obtained a Ph.D. degree in 1985 in exercise physiology from the University of Illinois, Urbana, IL.

     As a Research Assistant at the University of Illinois, Dr. Van Loan received extensive training in a full range of body composition methodologies from whole body 40K counting to skinfolds and underwater weighing.  She left Urbana, IL. in 1982 to assume a position with the  newly created USDA Western Human Nutrition Research Center (WHNRC) in San Francisco, CA.  Dr. Van Loan's responsibilities at the new Center included the development of a body composition laboratory for the assessment of nutritional status.

     At the WHNRC, her primary focus has been on the development and validation of new body composition methodologies.  She has conducted numerous studies to validate methods such as total body electrical conductivity (TOBEC), bioelectrical impedance analysis (BIA), dual energy xray absorptiometry, (DXA), and bioelectrical impedance spectroscopy (BIS).  More recently her research interests have shifted to the influence of eating behaviors and dietary patterns on bone integrity and weight loss.  She has published over 70 related articles in scientific journals and textbooks.

     Dr. Van Loan serves as a peer reviewer for numerous scientific journals such as the Journal of Applied Physiology, Medicine and Science in Sports and Exercise, and the American Journal of Clinical Nutrition.  In addition to her work as a peer reviewer, Dr. Van Loan is a Fellow in the American College of Sports Medicine and the Human Biology Council.  She has served as a member of the Program Planning Committee for the 1994 Nutrient Requirements and Functional Endpoints Meeting as well as for the 1998 Annual Meeting of the American Society for Clinical Nutrition and the 2006 and 2007 annual meeting of the American College of Sports Medicine.

Research Objectives

     To determine the three-year efficacy of isoflavone-rich soy extract in attenuating bone loss in postmenopausal women. The central hypothesis is that soy isoflavones will attenuate bone loss in early postmenopausal women by maintaining bone formation, modulated by growth factors and isoflavone metabolism. The rationale for this research is that current hormone therapy is fraught with side effects that adversely affect women, resulting in non-compliance. This randomized double-blind placebo controlled clinical trial is designed to examine the effects of two doses (80 or 120 mg/d) of isoflavone-rich soy extract on bone in non-osteoporotic early postmenopausal women (N=280). Specific Aims are to:  1) Determine the bone-preserving effects of isoflavones on bone mass and on serum markers of bone turnover; 2) Identify potential mechanisms of the effects of isoflavones in preventing bone loss and in modulating bone turnover by measuring endogenous estrogens, sex hormone-binding globulin, follicle stimulating hormone, and insulin-like growth factor-I (IGF-I) and its binding protein; 3) Evaluate the extent to which individual variability in isoflavone metabolism influences the effects of isoflavones on bone. Changes in bone mass and serum bone markers will be the primary bone outcomes. Multiple regression analysis will be used for each outcome to estimate the treatment effects, while accounting for ethnic group, customary intake of soy, bone biomarkers, baseline bone mass, reproductive hormones, IGF-I and its binding protein, circulating isoflavones, and other factors known to affect bone mass. This study will provide valuable data to help elucidate the mechanisms by which isoflavones impact bone in postmenopausal women, contributing to our understanding of isoflavones as an alternative to traditional hormone therapy.  This study is presently in the third year of intervention with the last research cohort expected to complete the 3 year intervention in May 2008.

     To determine how inclusion of 3 or more servings of dairy per day in a calorie-restricted diet changes the amount of visceral adiposity in overweight and obese subjects.  We are also conducting unique studies to evaluate the potential mechanism(s) by which dairy promotes weight and fat loss during dieting, through an examination of adipocyte size, gene expression, and inflammatory markers.  The hypotheses under investigation are (1) that inclusion of dairy foods in a modest energy restricted diet will significantly increase body fat loss compared to a control diet; (2) that dairy products in a modest energy restricted diet will result in greater fat loss from intra-abdominal adipose tissue compared to the control, 3) components of dairy products up- or down-regulate the secretion of metabolically-relevant hormones during the postprandial and inter-meal periods, 4) dairy products will promote satiety and/or satiation, 5) dairy foods reduce adipocyte differentiation and/or enhance adipocyte apoptosis, leading to concomitant white adipose tissue (WAT) expression changes for genes playing a role in these processes,  6) dairy foods will reduce adipocyte lipid storage and enhance pathways associated with thermogenesis and mitochondrial function in WAT, as reflected in gene expression changes and reduced adipocyte size, and 7) dairy foods included in a modest energy restricted diet will decrease inflammation in WAT and other tissues, thus decreasing circulating cytokines, improving zinc status, reducing expression of inflammatory markers in WAT, and reducing WAT macrophage infiltration.   In this project more than 60 research volunteers will be fed a diet with either 1 or less serving of dairy foods per day or 3 or more servings of milk, yogurt and cheese daily for 12 weeks.  Anticipated completion is December 2008.

Research Accomplishments

     Using multiplex luminex technology for simultaneous assessment of multiple cytokines we found a negative relationship among pro-inflammatory cytokines and bone mineral content in early postmenopausal women without hormone therapy.

     Evaluated the contribution of leisure time physical activity to bone strength and characteristics of bone geometry in postmenopausal women.  We found that a minimum of 4 hours of weight bearing leisure activity per week was needed to maintain cortical bone density and functional geometry.