September/October 2024

September/October 2024 Issue

The Power of Protein
By Stephanie Dunne, MS, RDN, IFNCP
Today’s Geriatric Medicine
Vol. 17 No. 5 P. 10

Optimizing Protein Intake to Maintain Robust Status in Older Adults

Ensuring that patients and clients experience the highest quality of life—remaining comfortable in their bodies and capable of participating in meaningful activities—is of utmost importance for health care practitioners. Proper nutrition is a critical component of health maintenance across all ages, and it becomes increasingly essential to maintain physical function as people age.

An older adult’s ability to ingest, digest, and metabolize sufficient amounts of protein can prevent the loss of skeletal muscle, thereby helping to sustain strength and mobility for a longer period of time. The aging process, however, introduces numerous challenges that can impede adequate protein consumption.

As individuals age, they face increased rates of muscle atrophy, diminished digestive capability, and reduced appetite, all of which make it difficult for older adults to ingest the protein necessary to preserve their health and vigor. “Adequate intake and digestion of protein is important for older adults for a number of reasons, including preventing or limiting loss of muscle mass, keeping a healthy immune system, fighting off infections or illness, and aiding faster recovery if they do get sick,” says Bailey Franklyn, RD, a registered dietitian and owner of Ontario-based Harvest Table Nutrition. Recognizing these physiological changes and implementing appropriate dietary strategies to optimize protein intake can help ensure that older adults maintain their vitality and independence longer.

Protein Needs and Average Intake in Older Adults
According to the Institute of Medicine, most healthy individuals aged 51 and older can meet their protein needs with an average daily intake of 0.8 g/kg of body weight or 0.36 g/lb of body weight, with no distinction made for those who are at least 65 years old.1 However, research studies suggest that optimal daily protein intake for healthy older adults might be higher—1 to 1.2 g/kg of body weight (0.45 to 0.55 g/lb). For older adults who are physically active or dealing with acute or chronic conditions such as sarcopenia and frailty, the recommended intake increases to 1.2 to 2 g/kg (0.55 to 0.91 g/lb).2-4 For older people with kidney disease not requiring dialysis, protein intake may need to be limited, as increased protein seems to deteriorate renal function in those with preexisting renal disease.2

Unfortunately, many older individuals fail to meet even the minimum recommended protein intake each day. The protein consumption of men between the ages of 60 and 70 often meets the 0.8 g/kg of body weight for men, but the same is not true for women. And by the age of 71, approximately 50% of women and 30% of men do not consume the Recommended Dietary Allowance (RDA) for protein.5

Impact of Inadequate Protein Ingestion
“As adults age, there is an increased risk of bone fractures and an overall decrease in muscle mass,” explains Moushumi Mukherjee, MS, RDN, a Michigan-based dietitian and owner of Dietitian Moushumi LLC. Both of these issues are closely linked to inadequate protein ingestion. Specifically, lower protein consumption has been associated with lower total body and spine bone mass density.6 Additionally, older adults with lower protein intake tend to exhibit decreased mobility, a lower percentage of lean body mass, and poorer performance on tasks that evaluate lower body physical capability.2

Inadequate protein intake has been shown to influence other functions as well. Research shows that older adults’ cognitive function, including memory and spatial learning, is negatively affected when protein intake is inadequate. Furthermore, higher levels of insoluble amyloid proteins, which have been linked to an increased risk of Alzheimer’s disease, are found in the brains of those with inadequate protein intake. Finally, dietary protein influences how the central nervous system communicates with the cardiovascular system, and inadequate levels may contribute to the development of cardiovascular diseases such as high blood pressure, diabetes, and obesity.2,4

Although it’s generally accepted that protein ingestion is one strategy to counteract the increased muscle protein breakdown seen in older adults, merely increased protein consumption may not be sufficient to preserve muscle strength and function. Keeping in mind that 43% of older adults are not meeting the RDA for protein, some studies have found no positive correlation between higher protein consumption and robust status, muscle mass, or strength for those older adults who are consuming at least the RDA.7-10 This discrepancy suggests that physiological changes associated with aging may influence both the ability to consume sufficient amounts of protein and the body’s ability to fully benefit from it.

Overcoming Oral Function Decline
Older adults may experience difficulties in chewing or swallowing due to dental issues or reduced oral strength. Fortunately, research suggests that older adults tend to increase their number of chews per bite to compensate for the decline in functionality.11 However, this loss of functionality may affect their choice to consume high protein foods, which may be tough, chewy, fibrous, and/or contain gristle, especially when eaten rare or undercooked.

To address these challenges, Franklyn says, “First, I would try changing the texture of high protein foods such as meat, poultry, or pork to see if minced or pureed forms allow for increased intake. Alternatively, consuming soft, protein-rich foods that are easier to chew, such as fish, eggs, Greek yogurt, cottage cheese, beans, and lentils, can help older adults reach their protein intake goals.” Mukherjee recommends enhancing the protein content of meals by adding cottage cheese or Greek yogurt to sauces and gravies, making foods softer and more palatable.

Managing Reduced Protein Digestion Capability
Aging also influences the stomach’s ability to digest food efficiently. In young adults, the pH of the resting stomach is quite low, rises when food is ingested, and falls again as the stomach produces hydrochloric acid to enable digestion. An acidic environment with plenty of pepsin—formed when hydrochloric acid and pepsinogen interact—is necessary for effective protein digestion, the release of vitamins B12 and D from the food matrix, and the conversion of iron to an absorbable form.

However, in older adults, the mean fasting pH of the stomach is significantly higher, and the stomach takes longer to return to an acidic state when food is present. Also, pepsin production is 40% lower for individuals older than 65 years of age compared with younger individuals, and fat digestion capability decreases by 80% by age 60, further affecting the stomach’s ability to digest meals containing both fat and protein. These physiological changes slow gastric emptying and reduce the completeness of protein digestion by the time the chyme enters the small intestine.11

Reduced secretion of trypsin—a key enzyme in protein digestion—by the pancreas into the small intestine of older adults exacerbates the problem of partial protein digestion. While small intestine transit time is maintained, reduced protein digestion means fewer amino acids, vitamin B12, vitamin D, and iron are absorbed into the body regardless of how much protein is consumed.11,12 Delayed and reduced absorption of these musclebuilding blocks may prevent or slow protein synthesis in aging muscles.13

To counteract these changes, “I suggest making every bite count,” Franklyn advises. “Prioritizing protein-rich foods first, rather than filling up on low-calorie or low-protein foods, can ensure older adults get enough of this important macronutrient.” She suggests a high-protein smoothie as a practical way to incorporate easy-to-digest protein.

Mukherjee adds, “Consumption of soup made with finely chopped meat and bone broth is a great way to get more easily digestible protein in the diet.”

If an older adult continues to lose muscle strength or mobility despite consuming adequate amounts of protein, digestive enzyme enhancers should be considered. Taking betaine hydrochloride with pepsin or a digestive enzyme supplement with a broader pH range with a meal can help return the stomach to an acidic condition while also providing the components necessary for protein digestion. A few drops of Swedish bitters tincture placed directly on the tongue or mixed into another liquid, such as sparkling water or herbal tea, can also enhance gastric acid function, as can drinking 1/2 to 2 tablespoons of apple cider vinegar diluted with room temperature or warm water.

Optimizing Protein Sources and Timing for Best Outcomes
The Dietary Guidelines for Americans 2020–2025 highlight that older adults generally have a higher diet quality compared with younger age groups.5 As such, the goal is to optimize protein sources and intake timing to best stimulate muscle protein synthesis with the goal of maintaining muscle mass and function.

Because older adults’ muscles are less responsive to low doses of protein intake, consuming 30 to 35 g of protein at each of the three main meals helps older adults achieve protein intake saturation, signaling the brain to promote muscle growth.4,7 Regular consumption of adequate protein at each meal is linked to greater lean body mass, higher gait speed, and improved lower-limb strength.7,10,14 Unfortunately, 42% of older adults do not consume at least 30 g of protein at any meal, and another 43.5% do so at only one meal. Breakfast and lunch are particularly deficient, with 91.5% and 77% of older adults, respectively, consuming less than 30 g of protein.8 Not reaching protein intake saturation at each meal may explain why some older adults experience loss of lean body mass even when meeting RDA.9 Therefore, Mukherjee emphasizes, “When optimizing protein intake, ensure protein is consumed throughout the day at all meal times and with snacks as well,” aiming for 30 g at each main meal.

Meeting the target of 30 g of protein in a single meal can be challenging for some older adults. For those who consume animal-based foods, approximately 5 oz of meat, poultry, or seafood will provide the necessary amount. In contrast, individuals would need to consume about five eggs or 11/2 cups of Greek yogurt to reach the same protein content. If meeting protein needs through food alone is difficult, a liquid protein supplement may be necessary, given how critical protein intake is to maintaining health, strength, and mobility. Whey protein, in particular, is easily digestible, rich in leucine, and more effective for muscle protein synthesis with lower doses than supplements like soy or casein.9,14

In addition to the timing of protein ingestion, the type of protein may also be a factor when optimizing protein status. Multiple studies have demonstrated that plant-based protein intake is associated with worse health outcomes, including lower bone mass density and reduced muscle protein synthesis, compared with animal-based protein.6,14 This difference may be because many plant-based proteins do not contain all of the essential amino acids and typically contain less leucine than animal-based proteins. Leucine is both a component of protein creation and an upregulator of the protein synthesis process.9 Prioritizing leucine-rich foods like pork, chicken, beef, and hard cheeses can therefore be beneficial but may not be a solution for all individuals. “Knowing an individual’s dietary restrictions and preferences is very important when meal planning or considering supplements,” Mukherjee says. Fortunately, for those who prefer a vegetarian or vegan eating pattern or who are not reaching protein intake saturation, supplementing with leucine can enhance muscle protein synthesis even when protein intake is not optimal.14

Additional Considerations
While optimizing protein intake is vital for maintaining health and functionality in older adults, other factors contribute to the loss of lean body mass and mobility in this population. Physical activity is essential to preserve muscle strength. Individually tailored exercises for both endurance and strength are required for maximum muscle protein synthesis when combined with adequate protein intake.3,7

Also, the impact of vitamin status on the relationship between protein intake and physical capability cannot be disregarded. For instance, supplementing omega-3 polyunsaturated fatty acids, such as those found in fish oil, has been found to increase muscle mass, strength, and function in older adults.14 Similarly, supplementation with vitamin D and calcium, along with leucine, has improved muscle mass in older adults with low serum vitamin D levels compared with those with adequate levels receiving the same supplements.15

Finally, Franklyn suggests that health care practitioners consider how medications and disease may affect an older adult’s appetite or protein digestion. These factors, along with mood disorders, inflammation, and chronic conditions like sarcopenia, can significantly influence the interplay between dietary protein and physical health.2

Key Takeaways
Optimizing protein intake is a fundamental aspect of maintaining health and functional capacity in older adults. Recognizing and addressing the unique challenges to protein consumption, digestion, and metabolism that aging poses allows health care practitioners to better support older adults in meeting their nutritional needs.

Personalized dietary strategies, including the selection of easily digestible and leucine-rich protein sources, along with appropriate timing and distribution of protein intake throughout the day, can significantly enhance muscle mass, strength, and mobility. For individuals who struggle to meet their protein requirements through food alone or for whom it is determined that protein digestion isn’t sufficiently effective, supplements such as whey protein and digestive enzymes can offer effective solutions.

Moreover, it’s essential to consider the broader context of each individual’s health status, including their physical activity levels, medication use, and potential vitamin deficiencies, when considering interventions to maintain or regain robust status.

As we continue to advance our understanding of nutritional needs in aging populations, it becomes increasingly clear that supporting optimal protein intake is a cornerstone of care for older adults. Doing so empowers older adults to remain active, resilient, and engaged in activities that preserve their robust status and contribute to a higher quality of life.

— Stephanie Dunne, MS, RDN, IFNCP, is an integrative registered dietitian, freelance writer, and owner of Nutrition Q.E.D. in St Petersburg, Florida.

References
1. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, D.C.: The National Academies Press; 2006. https://doi.org/10.17226/11537

2. Coelho-Júnior HJ, Milano-Teixeira L, Rodrigues B, Bacurau R, Marzetti E, Uchida M. Relative protein intake and physical function in older adults: a systematic review and meta-analysis of observational studies. Nutrients. 2018;10(9):1330.

3. Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559.

4. Baum JI, Kim IY, Wolfe RR. Protein consumption and the elderly: what is the optimal level of intake? Nutrients. 2016;8(6):359.

5. US Department of Agriculture; US Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf. Published December 2020.

6. Groenendijk I, Grootswagers P, Santoro A, et al. Protein intake and bone mineral density: Cross-sectional relationship and longitudinal effects in older adults. J Cachexia Sarcopenia Muscle. 2023;14(1):116-125.

7. Coelho-Júnior HJ, Rodrigues B, Uchida M, Marzetti E. Low protein intake is associated with frailty in older adults: a systematic review and meta-analysis of observational studies. Nutrients. 2018;10(9):1334.

8. Gaytán-González A, Ocampo-Alfaro MdJ, Torres-Naranjo F, et al. Dietary protein intake patterns and inadequate protein intake in older adults from four countries. Nutrients. 2020;12(10):3156.

9. Moore DR. Keeping older muscle “young” through dietary protein and physical activity. Adv Nutr. 2014;5(5):599S-607S.

10. Ten Haaf DSM, Van Dongen EJI, Nuijten MAH, Eijsvogels TMH, De Groot LCPGM, Hopman MTE. Protein intake and distribution in relation to physical functioning and quality of life in community-dwelling elderly people: acknowledging the role of physical activity. Nutrients. 2018;10(4):506.

11. Menard O, Lesmes U, Shani-Levi CS, et al. Static in vitro digestion model adapted to the general older adult population: an INFOGEST international consensus. Food Funct. 2023;14(9):4569-4580.

12. Ems T, St Lucia K, Huecker MR. Biochemistry, iron absorption. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2024. Updated April 17, 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448204/.

13. Milan AM, D’Souza RF, Pundir S, et al. Older adults have delayed amino acid absorption after a high-protein mixed breakfast meal. J Nutr Health Aging. 2015;19(8):839-845.

14. Witard OC, Wardle SL, Macnaughton LS, Hodgson AB, Tipton KD. Protein considerations for optimizing skeletal muscle mass in healthy young and older adults. Nutrients. 2016;8(4):181.

15. Kang Y, Kim N, Lee Y, An X, Chung YS, Park YK. Muscle mass changes after daily consumption of protein mix supplemented with vitamin D in adults over 50 years of age: Subgroup analysis according to the serum 25(OH)D levels of a randomized controlled trial. Clin Nutr Res. 2023;12(3):184-198.