UCSF DIABETES, ENDOCRINOLOGY & METABOLISM TRAINING PROGRAM FACULTY RESEARCH SUMMARIES

My research program centers on the effect of nutrition and environmental factors on skeletal metabolism which I have investigated through both smaller GCRC-based trials and large multicenter trials. The relationship between dietary protein intake and skeletal health during aging is complex, in part because different sources of dietary protein may have different effects on bone metabolism. Animal protein may increase fracture risk by providing a dietary acid load, leading to negative calcium balance and increased bone resorption. In contrast, vegetable sources of protein, while providing some acid due to their protein content, provide proportionally more base that counters the dietary acid load. The effect of dairy products, which are rich in animal protein but also contain potential base precursors not found in vegetable foods, has not been established. Finally, soy protein sources may have a dual benefit: soy foods provide base precursors as well as plant estrogens that may have a beneficial effect on bone.

Utilizing data from the Study of Osteoporotic Fractures, a multi-center observational study coordinated at UCSF, I demonstrated that women in this cohort with a high ratio of dietary animal to vegetable protein had increased bone loss and rates of hip fracture. Using this finding as preliminary data, I developed a randomized trial of four diets, equal in calories, protein, calcium, and sodium, but differing in that 80% of the protein comes from either animal, vegetable, dairy, or soy sources, with outcomes of calcium and acid-base metabolism in postmenopausal women. This study is in progress.

Pursuing the potential effects of alterations in dietary acid-base balance, I have been working to develop a multicenter randomized trial of alkaline potassium supplements. The treatment arms were selected based on the observation that thiazide diuretics lower urine calcium to a similar magnitude as potassium citrate and that the combination of the two agents has an additive effect on urine calcium-lowering. After reviewing the options for designing a smaller trial, I felt that the largest gap in knowledge and the area with the most intervention potential is a simple, two arm potassium citrate vs. placebo trial. This design addresses one of the most pressing research needs identified during the development of the Institute of Medicine's most recent dietary intake recommendations for minerals and has extensive public health implications. It tests an intervention that could both be easily implemented on a population basis and have a substantial impact on preventing the age-related deterioration in skeletal health.

I am also currently analyzing data from the Health, Aging, and Body Composition multicenter study in which I implemented a sub-study that measured arterialized venous blood gasses in the 3000 elderly participants in this cohort. We are examining the relationship between arterialized venous bicarbonate and musculoskeletal outcomes.

back to faculty list