Association between dietary phosphate intake and skeletal muscle energetics in adults without cardiovascular disease.

Highly bioavailable inorganic phosphate (Pi) is present in large quantities in the typical Western diet and represents a large fraction of total phosphate intake. Dietary Pi excess induces exercise intolerance and skeletal muscle mitochondrial dysfunction in normal mice. However, the relevance of this to humans remains unknown. The study was conducted on 13 individuals without a history of cardiopulmonary disease (46% female, 15% Black participants) enrolled in the pilot-phase of the Dallas Heart and Mind Study. Total dietary phosphate was estimated from 24-h dietary recall (ASA24). Muscle ATP synthesis was measured at rest, and phosphocreatinine (PCr) dynamics was measured during plantar flexion exercise using 7-T 31P magnetic resonance (MR) spectroscopy in the calf muscle. Correlation was assessed between dietary phosphate intake normalized to total caloric intake, resting ATP synthesis, and PCr depletion during exercise. Higher dietary phosphate intake was associated with lower resting ATP synthesis (r = -0.62, P = 0.03), and with higher levels of PCr depletion during plantar flexion exercise relative to the resting period (r = -0.72; P = 0.004). These associations remain significant after adjustment for age and estimated glomerular filtration rate (both P < 0.05). High dietary phosphate intake was also associated with lower serum Klotho levels, and Klotho levels are in turn associated with PCr depletion and higher ADP accumulation post exercise. Our study suggests that higher dietary phosphate is associated with reduced skeletal muscle mitochondrial function at rest and exercise in humans providing new insight into potential mechanisms linking the Western diet to impaired energy metabolism.NEW & NOTEWORTHY This is the first translational research study directly demonstrating the adverse effects of dietary phosphate on muscle energy metabolism in humans. Importantly, our data show that dietary phosphate is associated with impaired muscle ATP synthesis at rest and during exercise, independent of age and renal function. This is a new biologic paradigm with significant clinical dietary implications.

Evaluation of a Shelter-Based Diet and Physical Activity Intervention for Homeless Adults.

BACKGROUND: The current study evaluated the feasibility and effectiveness of a diet and physical activity intervention for homeless adults. METHODS: Shelter residents (N = 32) were randomly assigned to a 4-week diet and physical activity intervention (n = 17) or an assessment-only control group (n = 15). Intervention participants received tailored educational newsletters, pedometers with step goals, and twice daily fruit/vegetable snacks. Key measures included 24-hour dietary recall interviews and accelerometer-measured moderate-to-vigorous intensity physical activity (MVPA). RESULTS: At baseline, 68.8% of participants were overweight or obese, 93.8% reported food insecurity, and 43.8% reported activity levels below physical activity guidelines. Baseline dietary recall interviews indicated low fruit/vegetable consumption, and elevated intake of added sugar, saturated fat, and sodium relative to current dietary recommendations. During the 4-week study period, intervention participants engaged in significantly greater accelerometer-measured daily MVPA (P < .001) than controls (median = 60 daily minutes p vs. 41 daily minutes). Between groups differences in fruit/vegetable consumption at the end of treatment did not reach statistical significance. Most participants reported that the intervention was helpful for increasing fruit/vegetable intake and physical activity. CONCLUSIONS: Findings highlight the potential to improve dietary quality and increase physical activity among sheltered homeless adults.