Minimally processed animal protein is a premier source of essential macro and micronutrients in the diet and is important, especially to older adults who are at increased risk of nutritional deficiency and age-related physiological changes. Our central hypothesis is that adding lean animal protein within a healthy diet following macronutrient recommendations for Americans will enhance nutrient adequacy and attenuate markers of cognitive decline. This is a retrospective study leveraging samples collected from the feeding trial NCT05581953. PI for both studies are the same.

Inclusion Criteria:

• Generally, good health status based on one routine physical in the past 15 months, current health status
• Normal HbA1C, weigh 110 lb or more
• Age 65 years or more, generally healthy, all races and both sexes
• Generally practicing a meat-based dietary pattern, do not have any special dietary requirements, and
• Willingness to comply with the study protocol, including on-site meal consumption and sample/data collection.

Exclusion Criteria:

• Medication usage, probiotic, long-term antibiotic, and tobacco/drug/alcohol use
• Not on any special diet within 3 months of recruitment, and do not intend to lose weight
• Impaired kidney functions
• Active history of cancer, diabetes, heart, liver, and kidney diseases
• Major gastrointestinal disorders in the past 3 months
• History of heart attacks or stroke
• Unable to meet in-person visit requirements for dining, picking up meals, and tests
• Any mental health condition affecting the ability to provide written informed consent
• If they had not had a routine health checkup 12 months before recruitment.
• If they were unwilling to abstain from taking nutritional supplements, alcohol, non-study foods, and beverages during the study period.