A recent controlled feeding trial, published in the journal Current Developments in Nutrition, investigated the impact of integrating minimally processed red meat into a plant-forward diet on short-term biomarkers related to physical and cognitive aging in healthy older adults.
Study Objective
The research aimed to explore dietary patterns as modifiable risk factors for age-related conditions, particularly cognitive impairment like dementia, which is projected to affect 14 million Americans by 2060.
Study Design and Interventions
This crossover feeding trial recruited community-dwelling adults aged 65 years or older. Participants were randomized into two dietary interventions:
- Minimally Processed Pork (MPP) Diet: Participants consumed 162 g/day of minimally processed lean pork as the primary protein source.
- Minimally Processed Lentil (MPL) Diet: An equivalent amount of protein was provided from chickpeas, lentils, split peas, and black beans.
Both diets adhered to the 2020–25 Dietary Guidelines for Americans (DGA), incorporating plant foods, moderate amounts of eggs, dairy, and plant oils. Each intervention lasted eight weeks, separated by a two-week washout period. Participants abstained from non-study foods, alcohol, and specific supplements to maintain dietary control.
Outcome Measures
Blood samples were collected at baseline and after each dietary phase to measure a range of cardiometabolic, nutritional, and neuroactive biomarkers. These included triglycerides, glucose, high-density lipoprotein (HDL), total cholesterol (TC), insulin, ferritin, vitamin B12, brain-derived neurotrophic factor (BDNF), free choline, phosphatidylcholine, homocysteine, and biogenic amine metabolites (gamma-aminobutyric acid [GABA], glutamic acid, tryptophan, tyrosine, phenylalanine). Body composition was assessed via dual-energy x-ray absorptiometry (DXA), and muscle strength and function were evaluated using handgrip strength and chair-rise tests.
Key Findings
Of the 57 participants, 36 completed the full study protocol (average age 71, 72% female).
Both the MPL and MPP diets produced broadly similar short-term changes in biomarkers:
- Glucose: Decreased significantly after the MPL diet and non-significantly after the MPP diet.
- Insulin: Decreased in both phases, indicating improved insulin sensitivity.
- Total Cholesterol: Significantly lower after both phases, with no significant group differences.
- HDL: Lower across diets, but the reduction was smaller following the MPP diet, resulting in higher post-intervention HDL levels compared to the MPL diet.
- Triglycerides: Decreased by a smaller margin in both groups.
- BDNF: Showed a modest, non-significant increase after MPL but was unchanged with MPP.
- Choline: Serum choline levels were stable, but phosphatidylcholine was significantly lower after both MPP and MPL phases.
- Homocysteine: Levels increased modestly following MPP, primarily in a subgroup with elevated baseline concentrations, but remained unchanged after MPL. Vitamin B12 levels stayed within the clinical range, and ferritin increased in both groups.
- Neurochemical Markers: Both groups exhibited significant increases in GABA and reductions in its excitatory precursor, glutamic acid, alongside elevated levels of tryptophan, tyrosine, and phenylalanine.
- Body Composition and Physical Function: Body weight and lean mass decreased after both phases. Handgrip strength and lower-body function (chair stand test) remained stable.
Interpretation
The study concluded that plant-forward dietary patterns incorporating either minimally processed lentils or pork yielded broadly similar short-term changes in cardiometabolic, nutritional, and neuroactive biomarkers related to cognitive and physical aging. These results suggest that minimally processed red meat, when consumed as part of a DGA-aligned dietary pattern, may not be broadly unsuitable for older populations. The findings are based on short-term biomarker and functional measures, not clinical outcomes like cognitive decline or dementia, necessitating longer-term trials in more diverse populations for clinical relevance.