Email updates

Keep up to date with the latest news and content from Nutrition & Metabolism and BioMed Central.

Open Access Research

No protein intake compensation for insufficient indispensable amino acid intake with a low-protein diet for 12 days

Eveline A Martens1*, Sze-Yen Tan2, Richard D Mattes2 and Margriet S Westerterp-Plantenga1

Author Affiliations

1 Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, PO Box 616, 6200, MD Maastricht, The Netherlands

2 Department of Nutrition Science, Purdue University, West Lafayette, IN 47905, USA

For all author emails, please log on.

Nutrition & Metabolism 2014, 11:38  doi:10.1186/1743-7075-11-38

Published: 20 August 2014

Abstract

Background

Protein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days.

Methods

Two 12-day randomized crossover design trials were conducted in healthy subjects [n = 70/67 (M/F); age: 19-70 y; BMI: 18.2-38.7 kg/m2]. The relative dietary protein content was lower than [5% of energy (En%)], similar to (15En%), and higher than (30En%) customary diets. These diets had a limited variety of protein sources, containing wheat protein as a single protein source (5En%-protein diet) or 5En% from wheat protein with 10En% (15En%-protein diets) or 25En% (30En%-protein diets) added from whey with α-lactalbumin, soy or beef protein.

Results

There was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001). Nitrogen balance was maintained on the 5En%-protein diet, and was positive on the 15En%- and 30En%-protein diets (P < 0.001) over 12 days. Protein intake from the 5En%-protein diet did not reach the amount necessary to meet the calculated minimal IAA requirements, but IAA were sufficiently obtained from the 15En%- and 30En%-protein diets. In the 15En%- and 30En%-protein conditions, a higher protein intake from the soy-containing diets than from the whey with α-lactalbumin or beef containing diets was needed to meet the minimal IAA requirements.

Conclusion

Protein intake did not compensate for an insufficient indispensable amino acid intake with a low-protein diet for 12 days.

Trial registration

These trials were registered at clinicaltrials.gov as NCT01320189 and NCT01646749.

Keywords:
Protein intake; Nitrogen balance; Indispensable amino acids; DIAAS; Protein source