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Human Nutrition and Food Option
Professor, University of Wyoming, 1994-present
Associate Professor, University of Wyoming 1986-1994
Assistant and Associate Professor, University of North Carolina-Greensboro, 1980-1985
Ph.D. Human Nutrition - Virginia Tech, 1980
M.S. Human Nutrition - Virginia Tech, 1977
B.S. Plant Science - University of New Hampshire, 1974
Sports Nutrition and Metabolism (FCSC 3145),
Advanced Nutrition (FCSC 4145/5145),
Nutrition and Weight Control (FCSC 4147),
Nutritional Aspects of Proteins and Amino Acids (FCSC 5140), Carbohydrate and Ethanol Metabolism (FCSC 5141)
Current research interests primarily focus on food oxalate content and factors that affect the bioavailability of dietary oxalate. The effect of oxalate solubility in foods on oxalate absorption and urinary excretion is one major area of emphasis.
Oxalate is consumed in normal human diets as a component of nuts, fruits, vegetables, whole grains, and legumes. The calcium salt of oxalic acid is sparingly soluble in biologic fluids at physiological pH, and human tissues cannot degrade significant amounts of oxalate. Nephrolithiasis (kidney stones) is one of the most common of all clinical disorders with a prevalence typically ranging from 1 – 15 % in the general population. Kidney stones are three times more common men than in women with the peak age of occurrence between 30 – 50 years. About 80 % of all stones are composed of calcium oxalate, alone with a nucleus of calcium phosphate. Increased urinary oxalate is a risk factor for oxalate-containing kidney stones.
Research directed by Dr. Liebman demonstrated that oxalate absorption and urinary excretion are markedly reduced when oxalate consumption is accompanied by the ingestion of calcium. It appears that calcium binds with and ties up oxalate primarily in the small intestine, which is the major site of oxalate absorption. Consuming calcium-rich foods with high oxalate-containing meals is likely to decrease the risk of kidney stones in individuals predisposed to this disorder. More recent work from Dr. Liebman’s lab has suggested that in individuals characterized by high oxalate absorption levels, the ingestion of a probiotic containing bacterial species with oxalate-degrading activity can reduce gastrointestinal oxalate absorption, which could decrease risk of kidney stones and other disorders related to high levels of urinary oxalate excretion.
Al-Wahsh, I, Wu Y, Liebman M. A comparison of two extraction methods for food oxalate assessment. Journal of Food Research 2012;1:233-239.
Al-Wahsh I, Wu Y, Liebman M. Acute probiotic ingestion reduces gastrointestinal oxalate absorption in healthy subjects. Urological Research 2012;40:191-196.
Liebman M, Al-Wahsh I. Probiotics and other key determinants of dietary oxalate absorption. Advances in Nutrition 2011;2:254-260.
Okombo J, Liebman M. Probiotic-induced reduction of gastrointestinal oxalate absorption in healthy subjects. Urological Research 2010;38:169-178.
Okombo J, Liebman M. Oxalate content of selected breads and crackers. Journal of Food Composition and Analysis 2010;23:118-121
Liebman M, Okombo J. Oxalate content of selected pasta products. Journal of Food Composition and Analysis 2009;22:254-256.
Tang M, Larson-Meyer, E, Liebman M. Effect of cinnamon and turmeric on urinary oxalate excretion, plasma lipids and plasma glucose in healthy subjects. American Journal of Clinical Nutrition 2008; 87:1262-7.