The methods used to assess people’s nutrient requirements are not perfect, and newer and potentially better techniques may change recommendations over time.
For example, new techniques suggest that official recommendations for protein intake may be too low, especially for older people.
Recently, a team of researchers evaluated the protein requirements for older men using the indicator amino acid oxidation (IAAO) technique.
Today’s review provides a detailed summary of their findings.
Older adults arguably require greater amounts of protein than younger people.
Yet, the current dietary reference intake (DRI) and WHO recommendations are the same for young and old people.
Currently, they are the following:
- Estimated average requirement (EAR): 0.66 grams per kilogram (0.3 grams per pound) of body weight per day. The EAR refers to the intake level estimated to fulfill the requirements of half of the healthy individuals in the specified group.
- Recommended daily allowance (RDA): 0.8 grams per kilogram (0.36 grams per pound) of body weight per day. The RDA refers to the intake level estimated to fulfill the requirements of 97% of healthy individuals.
However, newer studies in older women have used the IAAO technique, which is newer and possibly more accurate (7).
Additionally, studies in older people with protein intakes equal to the current RDA suggest that they may lead to loss of muscle mass (10).
One working group even proposed that the recommendations for older people should be raised to 1.2–1.5 grams per kilogram (0.55–0.68 grams per pound) of body weight per day (11).
However, the evidence is limited and, until now, no studies have estimated the protein requirements of older men using the IAAO technique.
This study assessed the protein requirements of older men using the IAAO technique.
The purpose of this randomized, crossover trial was to assess the dietary protein requirements of six men, aged 65 or older, using the IAAO technique.
The participants received a total of seven different amounts of protein in a random order in different study periods, separated by one or two weeks.
The amounts of protein tested ranged from 0.2–2.0 grams for each kilogram (0.1–0.9 grams per pound) of body weight per day.
Each level of protein intake was tested over a 3-day period, starting with two adaptation days. On day three, protein requirements were assessed using the IAAO technique (13).
On the adaptation days, the participants received a weight-maintenance diet based on a lactose-free milkshake that provided 1 gram of protein per kilogram (0.45 grams per pound) of body weight per day.
On the third day, the participants arrived at the research center after a 12-hour fast. They then consumed eight hourly meals, each of which represented 1/12th of their daily calorie requirements.
The test day diet consisted of a protein-free liquid formula, Applesauce, grape seed oil and an amino acid mixture resembling the composition of egg protein.
Depending on the amount of protein being tested, the test meal provided 40% of calories from fat, 37–57% from carbs and 3–37% from protein. The diet provided 1.5 times the calories required for weight loss at rest.
Bottom Line: The purpose of this study was to assess the protein requirements of older men using the IAAO technique and compare the findings with previous studies using the same technique.
Finding 1: Protein Requirements of Older Men Are Higher Than Recommendations
The study showed that both the EAR and RDA for protein were higher than official recommendations.
- EAR: 0.94 grams per kilogram (0.43 grams per pound) of body weight per day.
- RDA: 1.24 grams per kilogram (0.56 grams per pound) of body weight per day.
The chart below compares the current findings with the official recommendations:
Simply put, the current EAR and RDA for older people may be underestimated by 30%.
However, before any strong conclusions can be reached, larger studies need to confirm the findings.
Bottom Line: This study suggests that the current recommended protein intake for older people may be underestimated by around 30%.
Finding 2: Protein Requirements May Increase with Age
The chart below shows the comparison of the EAR for protein between groups. Protein requirements are either expressed for each kilogram of body weight per day (BW) or for each kilogram of lean body mass per day (LBM).
The protein requirements for each kilogram of body weight were equal between all three groups. However, on the basis of lean body mass, they were higher in older men and women, compared to young men.
Bottom Line: Based on lean body mass, the protein requirements of older people were higher, compared to young people.
What Are the Health Effects of Inadequate Protein Intake?
Eating inadequate amounts of protein has adverse health effects, especially in older people.
These include the following:
- Muscle loss (sarcopenia) (14, 15).
- Decreased muscle strength and function (16, 17).
- Bone loss and an increased risk of fractures (18, 19, 20, 21).
- Reduced immune response, increasing the risk of infections (22).
Accordingly, one observational study showed that higher protein intakes were associated with fewer health problems in older people (23).
Bottom Line: Inadequate protein intake may promote muscle and bone loss and reduced strength. Additionally, it may impair the body’s immune response to infections.
This study had an excellent design, but one of its main limitations was the low number of participants.
Also, since the study used a marker of protein requirements, the true relevance of the findings need to be tested in long-term trials. However, conducting such trials may be difficult.
Finally, the body may be able to adjust to low protein intakes, but this study did not take such adaptations into account (24).
Summary and Real-Life Application
This study suggests that the current recommendations for protein intake among older men is underestimated by around 30%.
However, before the recommendations can be changed, the findings need to be validated by further studies.