(P16-028-23) The Minimum Methionine Requirement of Adults >60 Years Is the Same as Young Adults

Objectives: The primary aim of this study was to determine the minimum methionine requirement in healthy adult males and females ≥60 y using the indicator amino acid oxidation (IAAO) method and to compare the requirement estimates between older males and females. The secondary aim was to compare the requirement estimates in older adults to the previously derived IAAO requirement in young males.

Methods: The minimum methionine requirement was determined using the IAAO method with L-[1-¹³C]phenylalanine as the indicator. Fifteen adults (n = 7 males and n = 8 females; ³60 y; BMI £ 30 kg·m²) were assigned to receive 2 to 7 methionine intakes (0 – 20 mg · kg⁻¹· d⁻¹) in the presence of excess dietary cysteine (40 mg · kg⁻¹· d⁻¹) in random order. The mean minimum methionine requirement was determined from oxidation of L-[1-¹³C]phenylalanine (F¹³CO₂) using a biphasic linear mixed-effects model. The 95% CI was calculated using parametric bootstrap. To assess whether the breakpoints were different between older males and females or between older and young adults the overlap in the 95% CI was calculated. The null hypothesis was accepted if the interval contained zero.

Results: The mean minimum methionine requirement was the same in older males and females (Difference in CI: 0.8 ± 4.12) and so the data was pooled to determine a group mean. Biphasic linear regression analysis of the F¹³CO₂ data resulted in a breakpoint of 5.1 mg . kg-1. d-1 (R2 = 0.46, P < 0.01) and upper 95% CI of 6.53 mg . kg^-1. d^-1. The mean minimum methionine requirement of older adults was not different than the IAAO estimate in young males (Difference in CI: 0.5 ± 2.87).

Conclusions: This is the first study to estimate the minimum methionine requirement in older adults. The requirement determined in older adults is the same as young adults. These finding are especially relevant in light of the current recommendations for increased plant protein consumption, since methionine content is relatively less in pulses/legumes. The results will help in determining the appropriate balance of dietary sulfur amino acids – methionine+cysteine to satisfy the requirements of older adults.

Funding Sources: This study was funded by The Canadian Institute of Health Research. First author Alyssa Paoletti funded by Restracomp Scholarship provided by the Research Training Centre at SickKids Hospital.