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. 2023 Sep 23;15(19):4112. doi: 10.3390/nu15194112

Figure 2.

Figure 2

The effect of methionine intake with excess dietary cysteine on the production of 13CO2 from phenylalanine oxidation (F13CO2, mean ± SEM) by IAAO in older adults ≥ 60 years of age; n = 7 male and n = 8 female subjects; and 86 IAAO studies. Biphasic linear regression analysis of the F13CO2 data identified a breakpoint of 5.4 mg/kg/d for males (95% CI: 1.92, 8.88) and 4.6 mg/kg/d for females (95% CI: 2.40, 6.80), which represents the estimated mean minimum methionine requirement (A). The breakpoint for males and females combined was 5.1 mg/kg/d (Rm2 = 0.46, Rc2 = 0.77; p < 0.01) (B). The 95% CI of the combined estimate was 3.67 and 6.53 mg/kg/d. IAAO, indicator amino acid oxidation.