The Tryptophan Requirement in Healthy Adults
The aging population is growing rapidly. For the first time ever, Canadian seniors outnumbered young adults in 2016. Aging is associated with many physical and metabolic deteriorations including the loss of muscle mass and strength, insulin resistance, increased inflammation and oxidative stress.

The muscles of our bodies are composed of proteins and proteins are made of small building blocks called amino acids. Our bodies have the ability to make some amino acids which are called the non-essential amino acids. However, there are certain amino acids that our body's need to make protein but can only be supplied from the foods that we consume. These are called essential amino acids. Tryptophan is one of the essential amino acids that the body needs. Tryptophan is required for protein synthesis and acts as a precursor for serotonin and nicotinic acid. Therefore, there may be a need for more threonine in the diet of older adults. However, the current requirement for threonine is based on studies conducted exclusively in young adults. Thus, the purpose of this study is to find out how much tryptophan older adults need.
- EligibilityCriteria: Inclusion Criteria:  Consent provided. Aged 60 to 90 years old. In good general health as evidenced by medical history, physical health and blood draw. Fasting blood glucose, hemoglobin A1c (HbA1c), urea, creatinine. Willingness to participate in the study. BMI <30 kg/m2.  Exclusion Criteria:  Presence of chronic disease and/or acute illness known to affect protein/amino acid metabolism (e.g. HIV, diabetes, taking medications known to affect protein/AA metabolism (e.g. steroids). Inability to tolerate the diet (i.e. allergy). Significant weight loss during the past month or consumption of weight reducing diets. Significant caffeine consumption (>2 cups per day). Significant consumption of alcohol (>1 drink per day i.e. 1 beer or ½ glass of wine). Unwilling to have blood drawn from a venous access or using a ventilated hood indirect calorimeter for the purposes of the study. - HealthyVolunteers: Accepts Healthy Volunteers - Gender: All - MinimumAge: 60 Years - MaximumAge: 90 Years - StdAgeList: Adult, Older Adult