Protein Requirements Are Increased In Active Females As Determined By Indicator Amino Acid Oxidation
Bibliographic record
Abstract
PURPOSE: Protein requirements in athletes are generally greater than the current recommended daily allowance (RDA) based on nitrogen balance (NBAL), which may underestimate true requirements. Compared to males, less is known about requirements for this important macronutrient in active females. Therefore, the present study utilized the minimally-invasive Indicator Amino Acid Oxidation (IAAO) technique to evaluate the impact of variable intensity exercise on protein requirements of active females. We hypothesized the safe protein requirement would be greater than the RDA determined by both NBAL (0.8g/kg/d) and IAAO (1.2g/kg/d) in non-active adult males. METHODS: After a 2-d controlled diet, 7 females (~21y, ~63kg, ~23% body fat, ~47 mL O2/kg/min) completed 2–7 metabolic trials during the luteal phase that each involved the performance of variable intensity exercise (modified Loughborough Intermittent Shuttle Test) followed by 8 hourly mixed meals providing a variable protein intake (0.2-2.6g/kg/d), 6g/kg/d of carbohydrate, and sufficient energy. Protein was provided as crystalline amino acids modeling the amino acid profile of egg protein with the exception of tyrosine (40mg/kg/d) and the indicator phenylalanine (30.5 mg/kg/d with 5.46 mg/kg over 4h as L-[13C]phenylalanine). Breath13CO2 enrichment (isotope ratio mass spectroscopy) and CO2 production (indirect calorimetry) were used to calculate 13CO2 excretion (F13CO2) with bi-phase linear regression analysis used to determine the estimated average requirement (EAR) as the breakpoint and safe intake as the upper 95% CI. RESULTS: Preliminary analysis (n=33 trials) revealed F13CO2 conformed to a bi-phase model (r2=0.65; P<0.01) with an EAR for protein determined as 1.41g/kg/d and a safe intake of 1.76 g/kg/d. CONCLUSIONS: Our results suggest that the safe protein intake for active females during the luteal phase is 47-120% greater than the RDA in non-active individuals and is at the upper range of recommendations for athletes based on NBAL (i.e. 1.2-1.7g/kg/d, ACSM). Importantly, the EAR determined herein is similar to our previous study using the IAAO in active males (i.e. 1.35g/kg/d) suggesting that sex per se does not affect protein requirements after variable intensity exercise. Funded by the Ajinomoto Innovation Alliance Program.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".