This month’s newsletter was curated and edited by: Dr. J.W. Holloway and his Team
This discussion is preamble to a series of articles that will discuss in detail the nutrients supplied by the best food in the world, red meat. Red meat is the premium food because it provides readily absorbable nutrients in an abundance that are not available in any other food. These nutrients are classified as protein (the ten essential amino acids: threonine, tryptophan, histidine, arginine, lysine, leucine, isoleucine, methionine, valine, and phenylalanine), fat (the three essential fatty acids: linoleic, linolenic, and arachidonic), vitamins (especially the B vitamins) and minerals (especially iron). Since most consumers are unconcerned about getting enough fat, this discussion is limited to an introduction of red meat as a source of protein.
Protein and Amino Acids
Meat, especially red meat, is the preeminent source of human dietary protein. However, meat protein content can vary substantially. The average protein content is 22%; however, it can be as high as 34.5% (chicken breast) or as low as 12.3% (duck meat) (Pereira and Vicente, 2013). Meat protein is of high digestibility to humans as shown by the Protein Digestibility-Corrected Amino Acid Scores (PDCAAS). The highest PDCAAS of 1.00 have been reported for egg white and casein proteins. Meat scored 0.92, while pinto beans, lentils, peas, and chickpeas widely considered important protein sources in vegetarian diets scored from 0.57 to 0.71, and wheat gluten had a 0.25 score (FAO/WHO,1991).
Meat proteins also are balanced in terms of proportions of the essential amino acids. Even the non-essential amino acids, which can be produced by the human body, must have the dietary precursors in order not to be limiting. Inadequate consumption of amino acids, the primary units of proteins, can lead to protein malnutrition. Red meat is rich in protein that is digestible and has balance in the essential amino acids while also affording the building blocks for the synthesis of non-essential amino acids thereby being pre-eminent as a protein source for humans (Williams, 2007). Vegetarians must combine cereal and legumes to get all the essential amino acids. Cereals like rice and wheat are especially poor in lysine while legumes have low contents of methionine (Elango, Ball, and Pencharz, 2009).
Current recommended dietary allowances (RDA) in America for protein of 0.95 g/kg/d for children and 0.8 g/kg/d for adults were based on nitrogen balance studies which, because of the clouding effect of endogenous nitrogen, are imprecise (Binnie et al., 2014). The more precise indicator, the amino acid oxidation method, indicates protein needs are much higher (Elango et al., 2010, 2012) in the order of 1.3 to 1.55 g/kg/d for optimal growth and development of 6-10 yr. old children (Elango et al., 2011) and 1.1 to 1.5 g/kg/d for muscle and bone maintenance to reduce risk of age-related disabilities in adults (Gaffney-Stromberg et al., 2009; and Paddon-Jones and Rasmussen, 2009).
Binnie et al. (2014) summarized the effects of higher protein diets on weight maintenance in adults by concluding that higher protein diets are more effective in weight maintenance because they are associated with greater levels of satiety and lower total caloric intakes. Also, meta analyses conducted by Siri-Tarino et al., 2010 and Chowdhury et al. (2014) of 45 epidemiological studies and 27 controlled clinical studies on dietary data from more than 600,000 people in Europe, North America, and Asia concluded that there is no cardiovascular benefit of replacing saturated fat with carbohydrate.
Role of Amino Acids in Sarcopenia
Sarcopenia is an age-related muscle-wasting syndrome common to all people that results in a reduction in muscle mass and strength possibly leading to physical disability and morbidity (Cruz-Jentoft et al., 2010). Sarcopenia can be exacerbated by simultaneous obesity (sarcopenic obesity) (Thornell, 2011) and by diabetes (Srikanthan, Hevener, and Karlamangla, 2010). For uncomplicated sarcopenia, muscle mass decreases about 0.5–1.0% per year beginning at the age of 40 (Paddon-Jones et al, 2008). Factors thought to contribute to sarcopenia are age-related changes in food intake, changes in physical exercise, and chronic inflammation (Young et al., 2013). Treatment with testosterone and growth hormone only moderately alter the course of the disease, while treatment with growth hormone releasing hormone (GHRH) may have greater impact (Borst, 2004). However, a focused dietary intervention may have the greatest potential to counteract the onset or alter the course of sarcopenia (Young et al., 2013).
Increasing daily intake of protein above the requirement of 0.8 g/kg/d can reduce muscle loss that normally occurs with age (Paddon-Jones et al., 2008). Protein quality is also important in this regard in that it contains large amounts of the functional amino acid leucine, which stimulates protein synthesis by mTOR signaling (Du et al., 2007). Paddon-Jones et al. (2008) reported that a moderate intake of lean beef could increase muscle protein synthesis in both young and elderly men and women.
The most efficient intervention for reducing the effects of sarcopenia is resistance training (Young et al., 2013). Evans (2004) reported a synergistic effect of increased meat intake and resistance training allowing an increase in muscle mass in older men. In general, sarcopenia results from an imbalance in protein turnover. The mechanism underlying this synergistic effect involves the effect of the amino acid balance in meat on the activation of satellite cells resulting in muscle anabolism following resistance training (Thornell, 2011).
If something should be remembered, it is that red meat is one of the best proteins source (with a PDCAAS score of 0.92), better than the vegeterian ones. Not only red meat contains the essential amino acids but its comsumption enhances the production of other amino acids in our body. Moreover it boosts your child growth to the optimum while reducing risks of age-related disabilities you may have.
As it concerns many women and men nowadays, high protein diets will also work toward a better weight maintenance! Furthermore, it has been proven that there is no cardiovascular advantage from replacing saturated fat with carbohydrate. Plus, an increase of the daily intake of proteins above the requirement can reduce the effect of sarcopenia (potentialy more than the hormones treatments). Its effect will be reduced by regularly doing some sports too! As such, eating red meat is benefitial for your health!
Is red meat just a source of proteins though? Find out in the next post!