Men and women over 65 need more protein than nutritionists advise. That’s the message in two studies that Canadian nutritionists have published in the Journal of Nutrition. Not all their colleagues agree with them, but that’s not stopping this free webzine from sharing some of the information with you.
In 2015 and 2016 the researchers published studies on the protein requirements of men and women over the age of 65. [J Nutr. 2015 Jan;145(1):18-24.] [J Nutr. 2016 Mar 9. pii: jn225631. [Epub ahead of print].] For this the Canadians used the indicator amino acid oxidation technique. You can read more about this method here.
At present nutritionists use the nitrogen balance to determine protein requirements. For this you measure at different protein intakes the ratio between the amount of nitrogen a person consumes and the amount of protein that leaves the body. The requirement is the protein intake at which the two values are equal.
According to this method, both men and women over 65 need 0.8 g protein per kg bodyweight per day.
The Canadians discovered that the estimated average requirement [EAR] for women was 0.96 g protein per kg per day. A recommended daily amount [RDA] based on this would be 1.29 g per kg per day.
“Results generated using this approach provide validation to the increasing school of thought that the current protein recommendation for older adults is too low,” the researchers concluded.
Not all nutritionists agree with them. They believe that the method used is suitable for determining the best protein intake for a short period, but that it is not useful for determining protein requirements over a longer period. [J Nutr. 2015 Jan;145(1):5-6.]
Dietary Protein Requirement of Men >65 Years Old Determined by the Indicator Amino Acid Oxidation Technique Is Higher than the Current Estimated Average Requirement
The current estimated average requirement (EAR) and RDA for protein of 0.66 and 0.8 g ⋅ kg−1 ⋅ d−1, respectively, for adults, including older men, are based on nitrogen balance data analyzed by monolinear regression. Recent studies in young men and older women that used the indicator amino acid oxidation (IAAO) technique suggest that those values may be too low. This observation is supported by 2-phase linear crossover analysis of the nitrogen balance data.
The main objective of this study was to determine the protein requirement for older men by using the IAAO technique.
Six men aged >65 y were studied; each individual was tested 7 times with protein intakes ranging from 0.2 to 2.0 g ⋅ kg−1 ⋅ d−1 in random order for a total of 42 studies. The diets provided energy at 1.5 times the resting energy expenditure and were isocaloric. Protein was consumed hourly for 8 h as an amino acid mixture with the composition of egg protein with L-[1-13C]phenylalanine as the indicator amino acid. The group mean protein requirement was determined by applying a mixed-effects change-point regression analysis to F13CO2 (label tracer oxidation in breath 13CO2), which identified a breakpoint in F13CO2 in response to graded intakes of protein.
The estimated protein requirement and RDA for older men were 0.94 and 1.24 g ⋅ kg−1 ⋅ d−1, respectively, which are not different from values we published using the same method in young men and older women.
The current intake recommendations for older adults for dietary protein of 0.66 g ⋅ kg−1 ⋅ d−1 for the EAR and 0.8 g ⋅ kg−1 ⋅ d−1 for the RDA appear to be underestimated by ∼30%. Future longer-term studies should be conducted to validate these results. This trial was registered at clinicaltrials.gov as NCT01948492.