A DGA-aligned pulse-protein diet may support iron homeostasis in older adults: an exploratory analysis of the...

Iron homeostasis is essential for healthy aging, yet whether Dietary Guidelines for Americans (DGA)-aligned diets support iron status in older adults remains unclear, particularly when iron is provided exclusively as non-heme iron. This exploratory secondary analysis of PRODMED1 examined iron-related outcomes, and nutrient-responsive signals involving methionine and FGF21 in older adults consuming DGA-aligned meat- and pulse-protein diets.

In an 18-week randomized crossover controlled-feeding trial, adults aged ≥60 years (n = 47) consumed a meat-protein diet (MPD) and a pulse-protein diet (PPD) for 8 weeks each, separated by a ≥ 2-week washout. Diets were matched for total iron but differed in heme iron exposure and sulfur amino acid content. Exploratory correlation analyses were first used to identify nutrient-iron biomarker relationships, followed by multivariable predictive analyses (MVPA) evaluating methionine and FGF21 as nutrient-responsive predictors of iron-related outcomes.

PPD provided iron exclusively as non-heme iron and had lower methionine content than MPD. MPD increased serum methionine, cystine, and homocysteine (all p ≤ 0.004), whereas FGF21 increased significantly only after PPD (p = 0.038). Exploratory correlations identified diet-specific nutrient-iron biomarker relationships, supporting the selection of methionine and FGF21 for MVPA. In MVPA models, ferritin was the only iron-related outcome associated with nutrient-responsive predictors; methionine (β = +15.2 ± 3.6, p ≤ 0.0001) and FGF21 (β = +26.2 ± 10.5, p = 0.012) were independently and positively associated with ferritin, with no significant associations observed for total iron-binding capacity, transferrin saturation, or soluble transferrin receptor.

These exploratory findings suggest that a DGA-aligned pulse-protein diet may be compatible with maintained iron homeostasis in older adults despite exclusive non-heme iron intake. Methionine and FGF21 were associated with ferritin, suggesting a potential nutrient-sensing link, alongside established dietary and absorption-related determinants, both of which merit further clinical and mechanistic investigation. These findings also indicate that pulse-based protein sources may offer older adults additional shelf-stable dietary protein options, which is particularly relevant for rural communities with limited year-round access to fresh foods, without compromising iron homeostasis.