How often should you take protein?

If one was interested in philosophy, the above question is a perfect basis for creating countless scientific opinions. Unfortunately, this question does not have a straight answer. Numbers of experiments conclude with opposing results, and a lot is dependent on weight, age, the endocrine system, body mass without fat, and the fact whether the protein is ingested on its own or with other fats (the change in kinetics.)

If protein is ingested with glucose, or with fats and glucose, the existent reactions are much different. Macronutrients are also important, as well as the time of meal (different endocrine reactions take place in the morning and in the evening; insulin sensitivity is highest in the morning, and lowest in the evening.) In overweight women (BMI 37.1) a meal (1672kJ, i.e. ~400kcal) having 55% carbohydrates, 15% protein and 30% fats had different reactions than a meal consisting of 40% carbohydrates, 30% protein and 30% fats. After the meal consisting of 30% protein, the oxidation of fatty acids was noted as higher, than after the meal with only 15% of protein (but a higher amount of carbohydrates) – the same result was observed in groups of overweight and slimmer women (BMI 20.6). However, the pace of oxidation of glucose was not noted as any different in either group. In five overweight women, oxidation of fatty acids on an empty stomach was noted as much more efficient.

Parenteral feeding of new-borns noted the following results: intake of protein + glucose = higher processing of protein, higher breakdown of protein, and a higher level of oxidation of amino acids, compared to an intake of the same amount of protein but together with glucose and other fats. The level of protein synthesis was the same in both cases.

The above data considers the feeding of new-borns, but I would like to highlight that this may have an impact on bodybuilders, too. An often-used training efficiency marker is nitrogen balance. Bodybuilders in a research carried out by M. A. Tarnopolsky, et. al., ingesting 2.8g of protein per 1kg of body mass had fantastic results according to their nitrogen balance (there was an excess of between 12 and 20g of nitrogen a day). “Nitrogen balance compares the daily intake of nitrogen in the form of amino acids (protein) which the body is able to process with the daily loss of this element.” If nitrogen balance were a direct translation on the amount of muscle protein, one should be gaining between 300 and 500g of lean body mass a day (assuming that 75% of cells is water).

Moore supplied 24 young training men with protein. They exercised 4-6 times a week. They did exercises focusing on their legs – 5 series with the weight equal to 60-70% of their maximum, and later 4 series of 10 repetitions with the weight equal to 80% of their maximum. They were given protein within 12h after training. The first group of the men were given 80g of whey protein isolate (a portion of 40g given once every 6h), the second group were given 20g of WPI every three hours (four portions of 20g within 12h), and the third groups was given 10g of WPI every 1.5h (eight portions of protein within 12h).

Results

The highest level of synthesis of muscle protein took place in the first group (40g every 6 hours), and a little less in the second group (20g every three hours). However, the degradation of muscle protein in the second group (20g every three hours) was the lowest in comparison to the first and third groups (40g every six hours and 10g every 1.5 hours), so ultimately, focusing on the net protein balance, the most intake of 20g of protein every three hours was the most efficient.

Of course, the differences in the levels of muscle protein synthesis between the various intakes of protein at different times were minute, but on a three, six, or twelve month scale, those differences would be considerable.

References

1.Bresson JL1 Bader B Rocchiccioli F Mariotti A Ricour C Sachs C Rey J. “Protein-metabolism kinetics and energy-substrate utilization in infants fed parenteral solutions with different glucose-fat ratios” https//www.ncbi.nlm.nih.gov/pubmed/1907091
2.Tarnopolsky MA MacDougall JD Atkinson SA. Influence of protein intake and training status on nitrogen balance and lean body mass. J ApplPhysiol 1988;64
187 https//www.ncbi.nlm.nih.gov/pubmed/3356636
3.Grzegorz Kuciel Wiesława Łysiak-Szydłowska “Metody oceny niedożywienia i efektywności terapii żywieniowej” http//www.czytelniamedyczna.pl/8metody-oceny-niedozywienia-i-efektywnosci-terapii-zywieniowej.html
4.Stuart M Phillips “Protein requirements and supplementation in strength sports” https//www.researchgate.net/publication/8494999_Protein_requirements_and_supplementation_in_strength_sports
5.Labayen I1 Díez N Parra D González A Martínez JA. “Basal and postprandial substrate oxidation rates in obese women receiving two test meals with different protein content” https//www.ncbi.nlm.nih.gov/pubmed/15297093
6.Moore DR1 Areta J Coffey VG Stellingwerff T Phillips SM Burke LM Cléroux M Godin JP Hawley JA. “Daytime pattern of post-exercise protein intake affects whole-body protein turnover in resistance-trained males”. https//www.ncbi.nlm.nih.gov/pubmed/23067428

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