Protein bioavailability relates to how much protein the body absorbs and can potentially be used for normal healthy body function. Many protein product formulations are based on taste and convenience over bioavailability. That may serve the athletic/sports market but not the bariatric nutrition user.

Food and dietary supplements need to provide only what the body can absorb. Protein supplements are probably the most popular sports nutrition product on the market because of the interest in muscle building with proteins derived from a range of sources—whey, soy, hemp, pea, and algae. Bariatric patients are increasingly using the heavily marketed sports nutrition products for their source of high-protein supplements because of their lower cost and convenient availability.

Free Amino Acids versus Protein Powders

Amino acids are required for every function in the human body. Nine of the twenty amino acids required for synthesis of proteins cannot be produced in human tissues and must be provided by the diet. In addition, individual amino acids play an important part in producing hormones and neurotransmitters, detoxification of chemicals, and antioxidant protection along with bile acid production for digestion [45].

The need and pool of amino acids is so important for metabolism that therapeutic supplementation needs to be considered for each bariatric surgery patient because food proteins are slow to be digested and absorbed into the blood while amino acid needs are continually required for all tissues—gut, muscles, and brain.

Free amino acids are pure and have rapid uptake in the blood so they are available to reduce fatigue, promote DNA and RNA synthesis, and hormone production [46, p. 178]. Estimates of average protein intake required to sustain amino acid status are of VERY limited usefulness [46, p. 180]. Amino acid testing, which may be helpful for patients with chronic fatigue, depression, and bipolar disorders, is available. L-tryptophan is needed in every human tissue for rebuilding every cell yet many bariatric patients come into nutrition counseling on selective serotonin reuptake inhibitors (SSRI) drugs which deplete tryptophan. Without free amino acid supplementation, the dietary tryptophan needed for serotonin synthesis will not be met, resulting in mood, sleep, appetite, and neuropsychiatric disorders like depression, migraine, and anxiety [46, p. 183].

Bariatric nutrition protein supplements that are currently available on the market have insufficient research about the amino acid bioavailability of the protein sources and composition. Of particular concern is digestibility when lactose-containing products predominate the market.

Protein supplements made from whey—the waste product of the dairy industry’s cheese manufacturing—is exposed to acid processing and high drying temperatures that reduce bioavailability. In addition, the Journal of Food Science in October 2015 reported a study regarding the bleaching methods of whey protein isolates affecting functionality. Most of the fluid whey produced in the United States is derived from cheddar cheese curds with annatto coloring and needs to be bleached to remove the yellow color. The soluble protein level is decreased and protein degradation occurs [47].

As Stephan van Vliet et al. state in the Journal of Nutrition, efficacy of dietary strategies on muscle protein synthesis remains to be studied. The use of plant-based proteins versus animal-based proteins needs further evaluation. Grass-fed bovine milk and animal amino acids need to be compared with plant-based proteins with or without leucine supplementation [48]. A high whey protein, leucine and vitamin D3 enriched supplement was used to reduce the risk of sarcopenia [49]. Bojsen-Moller et al. reported that post Roux-en-Y gastric bypass (RYGB) basal plasma leucine concentrations did not change but caseinate digestion and amino acid absorption accelerated, resulting in faster and higher plasma amino acids [50]. The need for selected amino acid supplementation in bariatric formulas requires further research for improved patient health and well-being.

Bariatric surgery modifies the gastrointestinal tract, changing the pepsin and hydrochloric acid available for protein digestion. Reducing the stomach size changes the level of positively charged hydrogen (stomach acid) produced by parietal cells. These cells begin the digestion of protein ingested and activate pepsin, the main gastric enzyme produced by stomach cells. Without the intrinsic factor produced by parietal cells, transport of vitamin B12 to the ileum is compromised. Digestive enzymes may be needed by individuals unable to achieve healthy plasma albumin and protein levels.

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