Assessing the Influence of Habitual Beef Intake on Key Molecular Markers of Brain Health

Background and Rationale:

Cognitive decline and related dementias represent a growing public health crisis. While age and genetics are immutable risks, diet is a key modifiable factor for prevention and resilience. Lean beef provides a unique nutrient matrix-including vitamin B12, heme iron, zinc, selenium, creatine, and choline-that may support multiple aspects of brain structure and function. Recent advances in blood-based biomarkers now allow for the sensitive detection of neuropathological processes and neuroplasticity in response to lifestyle interventions. This project seeks to move beyond observational data to uncover the biological mechanisms that confer brain health by assessing the direct molecular impact of a dietary beef intervention.

Study Objectives:

The overarching goal of this study is to determine the impact of regular lean beef consumption on the molecular profile of brain health in healthy older adults. The primary aim is to quantify the within-person change in plasma phosphorylated tau-217 (p-tau217) following a 2-week lean beef intervention compared to a matched non-beef control. Secondary and exploratory aims include measuring within-person changes in the amyloid-beta 42/40 ratio (Aβ42/40) and Brain-Derived Neurotrophic Factor (BDNF), characterizing global shifts in the plasma lipidome, and exploring mechanisms of action via nutrient biomarkers.

Study Design:

The study is designed as a two-arm, randomized, controlled, crossover feeding trial. Twenty generally healthy adults (aged 65 years and older) will be block-randomized (1:1) to begin with either the intervention phase or the control phase.

Intervention Phase: Daily incorporation of 156 grams (5.5 oz) of lean beef for 14 days.

Control Phase: Daily incorporation of an iso-caloric, protein-matched non-beef control for 14 days.

A two-week washout period will separate the two phases to eliminate physiological carryover effects. Assignment of sequence will be randomized and counterbalanced to control for order and seasonal bias. Participants will maintain habitual eating patterns but will replace their daily protein sources with the study-provided food.

Methodology and Data Collection:

Clinical data and biological specimens will be collected at four distinct time points: the baseline and the conclusion of each 14-day dietary phase. At each clinical visit, fasted (12-hour) blood samples, as well as urine, stool, and saliva samples, will be collected. Basic anthropometric measurements, vital signs, and daily dietary records will also be obtained to monitor adherence and physical stability.

Outcome Evaluation and Analysis:

Targeted biomarkers of neurodegeneration and neuroplasticity (p-tau217, Aβ42/40, and BDNF) will be quantified using validated enzyme-linked immunosorbent assays (ELISA). Comprehensive untargeted lipidomic profiling will be conducted via Liquid Chromatography-Mass Spectrometry (LC-MS) workflows to identify lipid signatures associated with the intervention. Primary statistical analyses will utilize linear mixed-effects models to compare within-subject differences between the beef intervention and control conditions, adjusting for sequence and period effects. Appropriate statistical corrections will be applied for multiple comparisons and high-dimensional omics data.

Inclusion criteria

Adults aged 65 years and older.

Generally healthy with no acute illnesses.

Fluent in English.

Willing to consume lean beef and dairy products (cottage cheese and whey protein) daily during the intervention phases.

Willing to maintain current, habitual diet, physical activity levels, and body weight throughout the study.

Willing to fast for 12 hours prior to clinical visits and provide blood, urine, stool, and saliva samples.

Exclusion criteria

Diagnosed with Alzheimer's disease, Parkinson's disease, or other severe cognitive disorders.

History of gastrointestinal diseases (e.g., Crohn's disease, celiac disease) or major gastrointestinal surgery.

Uncontrolled diabetes, severe liver or kidney disease, or a recent cardiovascular event (within the past 6 months).

Allergies or severe intolerances to beef or dairy, or adherence to a strict vegetarian or vegan diet.

Body weight fluctuation of >5% within the past 3 months.

Use of systemic antibiotics within the 2 months prior to baseline.

Current heavy smoking or excessive alcohol consumption.