Dietary protein and functional decline in middle‐aged and older adults in the Framingham Offspring Study
Authors: Mustafa Jabed , Singer Martha R , Bradlee M. Loring , Ellison R. Curtis , Moore Lynn L 
Published: November 2023

In prospective studies and clinical trials in older adults, higher dietary protein intakes have been associated with greater preservation of lean body mass. This may in turn provide greater protection against age‐related functional decline. Prospective studies of diet and functional status in middle‐aged and older adults are needed. We used prospective data with up to 12 years of follow up for subjects in the Framingham Offspring Study (n=1894; 891 men and 1003 women) to examine the relationship between dietary protein and functional status and decline in adults ages 50 to 82 years at baseline. Diet was assessed via three‐day diet records at exams 3 and 5. Self‐reported functional status was measured at exams 5–8 using standardized instruments. For these analyses, we included the following outcome measures: heavy work at home, walking 1/2 mile, going up and down stairs, pushing/pulling heavy objects, stooping/kneeling/crouching, lifting <10 pounds, and lifting >10 lbs. Mean age was 56.5 ± 5.9 years at exam visit 5, the baseline visit for functional status change. Dietary protein intakes were expressed as grams of intake per kilogram (g/kg) of body weight. At each exam visit, subjects consuming the RDA (0.8 g/kg) for protein or more had lower risks of being dependent in these functional status measures. Since the protective effect of dietary protein was similar for those consuming 0.8–<1.2 or ≥ 1.2 g/kg (vs. <0.8 g/kg), final analyses were dichotomized as <0.8 vs. ≥0.8 g/kg (mean intakes in these two groups: 0.68 g/kg vs.1.14 g/kg, respectively). Multiple logistic regression analyses (binomial and multinomial) were used to adjust for potential confounding by age, sex, educational, physical activity, and smoking. At exam visit 5, subjects consuming ≥0.8 g/kg of dietary protein were 42% less likely (OR: 0.58; 95% CI: 0.43–0.78) to be dependent in one or more functional tasks. The effects persisted across subsequent exams and by exam visit 8, subjects were still 34% less likely (OR: 0.66, 95% CI: 0.49–0.90) to be dependent in one or more of these tasks. Further, at exam 8 we found that those consuming ≥0.8 g/kg of dietary protein had lower risks of becoming dependent in 1, 2, or 3 or more (vs. 0) functional tasks (ORs: 0.85, 0.60, 0.53, respectively (p‐trend<0.05)). Generally, the beneficial effects of dietary protein were stronger for women than for men. Finally, we examined the individual tasks that were most strongly impacted by protein intake and found that men consuming less than the RDA for protein were most likely to have difficulty with lifting and carrying heavier objects, doing heavy work at home, and walking ½ mile. Women with lower dietary protein intakes had difficulty with a wider range of tasks including lifting and carrying heavier objects, getting up from stooping/kneeling/crouching, walking ½ mile, going up and down stairs, and pushing/pulling heavy objects. These analyses suggest that adequate dietary protein intake may play a role in maintaining functional status over twelve years of follow‐up in middle‐aged and older adults.Support or Funding InformationNHLBI, Framingham Heart Study, (NHLBI/NIH Contract # N01‐HC‐25195) and the Boston University School of Medicine