Digestion of sorghum protein might be lower in older adults

In a randomized crossover study, 10 young adults aged 20 to 35 and 10 older adults aged 65 to 80 ate meals with 20 grams of protein from milk, sorghum, or black beans on three separate test days. The protein was labeled with a hydrogen isotope and served with free amino acids labeled with carbon-13. Blood was sampled over eight hours to measure tracer levels in plasma. The researchers focused on lysine and threonine, two indispensable amino acids that avoid transamination, an internal metabolic reaction that transfers chemical groups between molecules. Across all three protein sources combined, digestibility did not differ significantly by age. For sorghum alone, the tracer ratio for lysine and threonine was 19% lower in older adults than in younger adults, while milk and black beans showed no significant age differences.