Nutrition to prevent frailty

Nutritional intake for the prevention and management of frailty

1. Frailty and Malnutrition
   • -The older people are prone to malnutrition due to unbalanced dietary habits caused by aging-related deterioration in physiological function, social psychological isolation, illness and medications, decreased activity, incorrect eating habits, and poor nutritional knowledge (Lee, 1999).
   • -The Cardiovascular Health Study (Fried et al., 2001) and the InCHIANTI study (Bartali et al, 2006) reported that nutritional deficiency was associated with sarcopenia and frailty. Millne et al. (2006) conducted a meta-analysis and also found that when oral nutritional supplements were administered to malnourished older people patients, complications and mortality of the inpatients decreased.
2. Frailty and Proteins
   • -Among the nutrients affecting frailty, protein is the most frequently studied nutrient; a study in Koreans showed that the higher the protein intake, the lower the likelihood of falls (Gang et al., 2009).
   • -Overseas nutritional intervention studies also have reported that protein supplementation improved the frailty score, muscle strength of lower extremities, scores in simple physical function test, standing up from a chair, and walking after standing up from a chair in the older people diagnosed as frailty or pre-frailty (Ng et al, 2015; Bauer et al, 2015; Tieland et al, 2012; Verreijen et al, 2015).
   • -However, unfortunately, the conclusion has not been reached as to how much protein intake is appropriate for the older people.
3. The Amount of Proteins and Sarcopenia
   • -There are more studies on the effects of protein intake on sarcopenia than those on the relationship between frailty and protein; sarcopenia is also a major indicator of frailty (Fried et al, 2001).
   • -Sarcopenia is a common condition observed in the older people and its connection to malnutrition, particularly poor protein intake, is universally accepted without objections (Cruz-Jentoft et al, 2010); several nutritional intervention studies have shown that muscle mass increased by protein supplementation, which also led to prevention of sarcopenia (Aleman-Matero et al, 2012; Solerte et al, 2008; Katsanos et al, 2006). On the other hand, another study reported that at least 20g of protein/meal was required for older people with sarcopenia (Campbell et al, 1997).
   • -It was reported that when 0.8g/kg of protein was provided to older people, an increase in nitrogen excretion to urine and muscle loss were observed, suggesting that their protein intake was not sufficient (Campbell et al, 2001). In addition, a nutritional intervention study, in which 1.1g/kg or 1.3g/kg of protein was provided to malnourished older people for 12 weeks, showed that the respiratory muscle strength was improved in the 1.3g/kg protein intake group (Smoliner et al., 2008); there was another report showing that when older people men and women consumed 1.2 g/kg of protein rather than 0.9 g/kg, their lean body fat increased while their body fat decreased (Iglay et al., 2007). Likewise, the Health ABC epidemiological study also reported that the older people group that consumed 1.2 g/kg of protein showed less reduction in their lean body fat than the older people group that consumed 0.8 g/kg of protein (Houston et al, 2008).
   • -When setting the recommended amount of protein, 0.8 g/kg of protein would be appropriate if it is set focusing on nitrogen equilibrium. However, considering elevated metabolism, especially oxidation, of amino acids in older people, some people suggest that 1.15-1.29 g/kg is more appropriate (Humayun et al., 2007 ; Elango et al., 2011; Tang et al., 2014; Stephens et al., 2015)
   • -Recently, the PROT-AGE Study Group recommended 1.2 - 1.5g/kg of protein for older people with chronic or acute illness and 2.0g/kg for malnourished older people with severe illness or injury (Bauer et al, 2013).
   • -The recommended amount of protein intake for the older people in Korea has been set to the same as for adults at 0.8 g/kg. However, considering that catabolism is more robust than anabolism in the protein metabolism of the older people, the current recommended amount of protein intake may not be sufficient (Evans, 2004).
   • -According to the National Health and Nutrition Survey, the amount of protein intake was lower than the recommended amount in more than 30%of people, and protein intake was decreased in both men and women as age increased (National Health and Nutrition Survey, Figure 1). Therefore, appropriate measures should be taken to increase protein intake for the older people in Korea.

Figure 1. Trend of Protein intake in both men and women as age increased

(National Health and Nutrition Survey)

1. Protein Types and Sarcopenia
   • -There have been studies reporting that different protein types, that is, amino acid compositions, have different effects on the inhibition of muscle loss. It has been reported that the intake rate of essential amino acids is important for the prevention of sarcopenia in the older people, and another study also showed that intake of animal proteins is associated with muscle mass (Paddon-Jones & Rasmussen, 2009).
   • -Meta-analysis of nine studies which compared carbohydrates in proteins from milk, wheat, and soybeans has shown that wheat protein inhibited the reduction of lean body fat (Phillips et al, 2009). Wheat protein has a higher content of leucine than milk, casein, and soybeans, and there was also a report that leucine increases the synthesis rate of muscle proteins (Pennings et al, 2011).
   • -In a randomized, double-blind, placebo-controlled study, in which leucine was administered to older people with sarcopenia, limb muscle mass was significantly increased (Bauer et al, 2015).
   • -Leucine is rapidly absorbed. It is known to not only act as a substrate for protein synthesis, but also inhibit protein catabolism and promote protein synthesis by involving in the expression of the mTOR protein (Phillips et al, 2009).
   • -Beta-hydroxy-beta-methylbutyrate (HMB), a derivative of leucine, reduces exercise-related muscle damage, increases or preserves muscle mass, inhibits protein breakdown, and increases protein synthesis (Molfino et al, 2013).
   • -Of the double-blind placebo-controlled clinical intervention studies in which 2 to 3 g of HMB was administered, six studies were conducted in older people, and most of these studies showed that HMB was effective in suppressing loss of muscle mass. It is also expected to be effective in preventing frailty, which requires further research.