(P09-033-25) A Cross-Sectional Analysis of Dietary Tryptophan Intake and Serum BDNF in Older Adults With Mild Depressive Symptoms

Objectives: Brain-derived neurotrophic factor (BDNF) is an important neurotransmitter in the brain that has a putative role in preventing depression in older adults. Studies in aging rats found that diets supplemented with high levels of tryptophan increased expression of BDNF in the brain. However, whether this association translates to older adults is unclear. The objective of this work is to determine the association between dietary tryptophan with serum BDNF in older adults. We hypothesize that higher dietary tryptophan intake is associated with higher concentrations of serum BDNF.

Methods: This cross-sectional analysis was conducted on 22 older adults (≥65 years) with mild depressive symptoms who enrolled in a dietary intervention. Three day averaged dietary intake of tryptophan was estimated from 3-day diet records that were entered into Nutrition Data System for Research (NDSR) software. Serum BDNF levels were measured in fasting blood samples using a commercially available enzyme-linked immunosorbent assay. Linear regression estimated beta and standard error (SE) for BDNF per 1 g/day higher intake of dietary tryptophan, adjusting for age, sex, and calories.

Results: Participants were mean age 73 ± 5, 77% female, and 90% white. Mean dietary tryptophan intake was 0.83 ± 0.37 grams/day and mean serum BDNF was 39.1 ± 15.1 ng/mL. There was no association between dietary tryptophan intake and BDNF levels in older adults (beta: -3.1, SE: 9.2, p=0.74). Results did not change after adjusting for select covariates (beta: -8.5, SE: 10.8, p=0.44).

Conclusions: In our small sample, there was no association between dietary tryptophan and serum BDNF. This study is limited by a small and non-diverse sample size. It is possible that dietary tryptophan may not impact peripheral serum BDNF or that the levels of dietary tryptophan intake in our population were below the threshold that may be necessary to impact BDNF in serum. Replication of our analyses in a larger, more diverse sample would be more informative.

Funding Sources: This work was funded by the NIA Grant# P30AG048785.