Development of a Novel Method to Study in Vivo Fatty Acid Metabolism Using Stable Isotope Labeled Fatty Acids in Humans

Vegetable oils high in the specific fatty acids of interest - stearic (found in cocoa butter, meats), palmitic (found in meats, dairy and some plant oils) and stearic acid's metabolic product, oleic (found in olive and corn oil) - will be used to displace each other in a standardized diet and fed to mildly hypercholesterolemic postmenopausal women using a randomized-controlled crossover design. Six women who are enrolled in 10150 - Study A will be invited to participate in this study. Each of the phases will be 5 weeks in length with a 2-4 week break between phases. All food and drink will be provided to study volunteers. Blood pressure and body weight will be monitored once per week and adjustments made, if necessary, to maintain a stable weight. During week 1 of the 18:0 and 18:1 dietary phases, a fasting blood sample will be drawn. A single stool sample will be collected on any of the study visits after week three. On Day 1 of week 5, following a 12 hour fast, each volunteer will receive their usual diet divided into 15 hourly small meals. A purified tracer dose (1 mg/kg bodyweight \[BW\]) of 13C fatty acid will be incorporated into the 1pm meal. Blood samples will be collected from a catheter inserted into the subcubital vein just before consuming the first hourly meal and then 2, 5, 7, 8, 9, 11, 13 and 15 hours thereafter. Breath samples will be collected before the first hourly meal as well as at various time-points after. Additional fasting blood samples will be collected on Days 2, 3, 4 and 5 of the 18:0 and 18:1 diet phases. At the end of Day 1, volunteers will have the option of returning home or staying overnight at the Jean Mayer Human Nutrition Research Center.