THE EARLY YEARS OF LIFE--FROM CHILDHOOD THROUGH ADOLESCENCE--ARE A CRITICAL TIME FOR SETTING THE FOUNDATION FOR LIFELONG HEALTH. WHILE MANY STUDIES HAVE LOOKED AT NUTRITION AFFECTS DURING GESTATION AND LACTATION, THERE'S MUCH LESS RESEARCH ON HOW WHAT CHILDREN AND TEENS EAT IMPACTS THEIR HEALTH AS ADULTS. THIS IS ESPECIALLY CONCERNING, BECAUSE NATIONAL DIETARY DATA SHOWS THAT MOST CHILDREN AND TEENS IN THE U.S. HAVE POOR DIETS--SCORING BELOW 55 OUT OF 100 ON THE HEALTHY EATING INDEX. BREAST CANCER IS THE MOST COMMON CANCER AMONG FEMALES IN THE UNITED STATES, WITH OVER 310,000 NEW CASES EXPECTED IN 2024 ALONE. IT ALSO REMAINS THE SECOND LEADING CAUSE OF CANCER-RELATED DEATHS IN FEMALES. WHILE ADVANCES IN SCREENING AND TREATMENT HAVE HELPED REDUCE DEATH RATES SINCE 1990, THE NUMBER OF NEW BREAST CANCER CASES CONTINUES TO RISE--ESPECIALLY AMONG YOUNGER FEMALES. ALARMINGLY, ABOUT HALF OF FEMALE WHO DIE FROM BREAST CANCER IN THE U.S. TODAY ARE UNDER THE AGE OF 45. ONE KEY GAP IN OUR UNDERSTANDING IS WHY BREAST CANCER IN YOUNGER FEMALE HAS BEEN INCREASING OVER THE PAST 50 YEARS. OUR PROJECT AIMS TO EXPLORE WHETHER POOR WESTERN-STYLE DIET (WSD) DURING CHILDHOOD AND ADOLESCENCE PLAYS A ROLE IN THIS TREND--AND IF IMPROVING EARLY-LIFE NUTRITION COULD HELP PREVENT BREAST CANCER LATER ON. IN OUR EARLY STUDIES USING ANIMAL MODELS, WE FOUND THAT EATING A HIGH-FAT DIET DURING YOUTH LED TO LONG-LASTING CHANGES IN THE GUT MICROBIOME AND IN BREAST TISSUE--CHANGES THAT MAY INCREASE THE RISK OF DEVELOPING BREAST CANCER LATER IN LIFE. THESE FINDINGS SUGGEST THAT THE RISE IN BREAST CANCER AMONG YOUNG FEMALE MAY BE LINKED, AT LEAST IN PART, TO THE INCREASING POPULARITY OF WESTERN-STYLE DIETS, WHICH ARE OFTEN HIGH IN FAT AND LOW IN FIBER AND ESSENTIAL NUTRIENTS. BEANS ARE A POWERFUL, NUTRIENT-RICH FOOD THAT CAN HELP IMPROVE THE QUALITY OF WSD. THEY CONTAIN FIBER, PROTEIN, AND OTHER IMPORTANT NUTRIENTS THAT MANY PEOPLE IN WESTERN COUNTRIES DON'T GET ENOUGH OF. HOWEVER, WE STILL DON'T KNOW ENOUGH HOW EFFECTIVE TO INCORPORATE BEANS INTO WSD FOR CHILDREN AND ADOLESCENTS AND THEREBY TO PROMOTE BREAST HEALTH, REDUCING THE RISK OF EARLY-ONSET BREAST CANCER. THIS PROJECT WILL FOCUS ON THREE MAIN GOALS: 1) TO EXAMINE HOW ADDING BEANS TO A WESTERN-STYLE DIET DURING CHILDHOOD AFFECTS THE GUT AND BREAST HEALTH LATER IN LIFE; 2) TO INVESTIGATE WHETHER THIS DIETARY CHANGE CAN REDUCE THE RISK OF DEVELOPING BREAST CANCER IN ADULTHOOD; AND 3) TO UNDERSTAND THE ROLE OF THE GUT MICROBIOME IN CONNECTING EARLY-LIFE DIET TO BREAST HEALTH OUTCOMES. BY EXPLORING THESE QUESTIONS, WE HOPE TO DEVELOP PRACTICAL, SCIENCE-BASED DIETARY STRATEGIES TO HELP REDUCE THE RISK OF BREAST CANCER--STARTING WITH BETTER NUTRITION IN THE EARLY YEARS OF LIFE.