Exploratory Analysis of the PRODMED1 Trial Suggests Pulse-Protein Diet Supports Iron Homeostasis in Older Adults

An exploratory secondary analysis of the PRODMED1 trial indicates that a Dietary Guidelines for Americans (DGA)–aligned pulse-protein diet may aid in maintaining iron homeostasis in older adults, even when iron is consumed exclusively as non-heme iron. The analysis involved adults aged 60 and older who participated in an 18-week randomized crossover controlled-feeding trial, which included two diets: a meat-protein diet (MPD) and a pulse-protein diet (PPD), each lasting eight weeks with a two-week washout period in between. Both diets were matched for total iron content but differed in heme iron exposure and sulfur amino acid composition.

Forty-seven participants completed both dietary phases. The PPD provided non-heme iron exclusively and had lower methionine content than the MPD. Results showed that the MPD increased serum methionine levels, while significant increases in fibroblast growth factor 21 (FGF21) were observed only after the PPD. Correlation analyses identified relationships between diet-specific nutrients and iron biomarkers that justified further evaluation using multivariable predictive analyses (MVPA).

Multivariable analyses revealed that ferritin was significantly correlated with both methionine and FGF21. Specifically, higher levels of methionine predicted increased ferritin levels (β=15.2, p≤0.0001), as did higher levels of FGF21 (β=26.2, p=0.012). However, no significant associations were observed with total iron-binding capacity, transferrin saturation, or soluble transferrin receptor.

These findings suggest that a DGA-aligned pulse-protein diet may be effective in supporting iron homeostasis among older adults, challenging the notion that plant-based diets are inferior for maintaining iron status. Further research is needed to confirm these results and explore the underlying mechanisms, particularly the interactions between methionine, FGF21, and ferritin within the context of dietary patterns.

The PRODMED1 study underscores the complexities of iron metabolism in aging and emphasizes the potential role of pulse-based protein sources as a viable and affordable dietary option, particularly in rural settings where access to fresh foods may be limited.