**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** IN GENERAL, DIETARY SATURATED FATTY ACIDS (SFAS) ARE CONSIDERED UNHEALTHY BECAUSE OF THEIR ADVERSE EFFECTS ON CARDIOVASCULAR DISEASE (CVD) RISK FACTORS. HENCE, THE DIETARY GUIDELINES FOR AMERICANS (DGA) RECOMMENDS THAT THE INTAKE OF SFA BE LESS THAN 10% OF THE TOTAL DAILY FAT INTAKE. THIS GENERALIZED GUIDELINE GROUPS ALL SFAS TOGETHER INCLUDING STEARIC ACID (18:0), WHICH IS ONE OF THE MAJOR SOURCES OF DIETARY SFAS IN OUR DIETS. HOWEVER, DATA ACCUMULATED OVER THE PAST 50 YEARS INDICATE THAT 18:0 IS UNIQUE AMONG THE SFAS, AS IT HAS A NEUTRAL EFFECT ON BLOOD LIPID PROFILES, AND DOES NOT INCREASE CVD RISK. THIS HAS LED TO THE SUGGESTION THAT 18:0 NOT BE GROUPED TOGETHER WITH OTHER UNHEALTHY SFAS ON FOOD LABELS.ALSO PROPOSEDIS THAT 18:0 BE USED TO REPLACE UNHEALTHY TRANS FATTY ACIDS IN THE FOOD SUPPLY. HOWEVER, WE STILL NEED TO FULLY UNDERSTAND 18:0 METABOLISM AND ITS METABOLIC CONSEQUENCES WITHIN THE BODY BEFORE IMPLEMENTING ANY CHANGES. THIS PROJECT WILL ADDRESS THIS BY DETERMININGIF THENEUTRAL EFFECTS OF DIETARY 18:0 ON CVD RISK IS MODULATED BY GUT MICROBIOTA AND COMPOUNDS PRODUCED IN THE GUT (CALLEDMICROBIAL METABOLITES) ON HOST METABOLISM. WE WILL USE A COMBINATION OF TECHNOLOGIES (METAGENOMICS AND METABOLOMICS) TO MEASURE GUT MICROBIOTA COMPOSITION AND FUNCTION, AS WELL AS VARIOUS METABOLITES IN STOOL AND BLOODSAMPLES COLLECTED FROM POSTMENOPAUSAL WOMEN WHO PARTICIPATED IN A RANDOMIZED, CONTROLLED CLINICAL TRIAL. PARTICIPANTSWERE FED ADIETENRICHED IN A VEGETABLE OIL WITH A HIGH 18:0 CONTENT (FULLY HYDROGENATED COTTONSEED OIL) AS WELL AS A FAT NATURALLY HIGHIN 18:0, (COCOA BUTTER), AND 2 ADDITIONALDIETS CONTAINING OTHER MAJOR VEGETABLE OIL SOURCES, NAMELY 16:0 (PALM OIL) AND 18:1 (HIGH OLEIC SAFFLOWER OIL). RESULTS FROM THIS STUDY WILL PROVIDE A DEEPER UNDERSTANDING OF THE EFFECTS OF CONSUMING DIETARY 18:0, AND CONTRIBUTE TOWARD BOTH ONGOING EFFORTS TO OPTIMIZE DIETARY SFA GUIDELINES/FOOD LABELSAND IDENTIFYING ADDITIONAL VEGETABLE OIL/FAT ALTERNATIVES TO REPLACE TRANS FATTY ACIDS IN THE FOOD SUPPLY.