A good friend and leading researcher in the field of protein metabolism (Dr Burd) has published a number of studies that show the benefits of eating protein from the whole food (matrix) is required to get the optimal benefits from amino acids - see this paper for one example. https://doi.org/10.1016/j.tjnut.2023.02.037. Linked to this point, is my suggestion that eating protein from an isolate supplementation form is less beneficial than eating an egg. After all, protein supplementations are a processed food type, much in the same way as a processed ready meals, which we all know we should avoid.
Some of my own research is investigating the possible role that over consumption of protein could lead to insulin resistance, elevated blood insulin and type 2 diabetes. Indeed, similar to sugar, carbohydrates, and fat intake (i.e. nutrient overload), excessive protein ingestion has the potential to cause in insulin resistance as the cell becomes overwhelmed with energy and switches off its ability to take more energy onboard (fat, CHO and protein). See one of our papers as an example - DOI: 10.1139/apnm-2020-0396.
To better understand the relationship between protein intake and insulin / insulin resistance, we really need to understand what happens when humans consume this energy source. After all, eating / drinking protein supplementations extend well beyond just building muscle in the human body. For example, eating protein also has a signalling action on the liver, one of the most important tissue types in the human body.
When it comes to insulin's metabolic actions on the liver in response to protein ingestion, the focus shifts to how insulin influences various metabolic processes in the liver. Here are some key points regarding insulin's effects on the liver in response to protein ingestion:
1. Inhibition of Gluconeogenesis (i.e. slows down the production of sugar from non-sugar sources): Insulin helps to slows down gluconeogenesis, which is the process by which the liver produces glucose from non-carbohydrate sources like amino acids (derived from protein), lactate, and glycerol (or fat). When you consume protein, insulin levels rise, signaling the liver to reduce the production of glucose from these energy molecules.
2. Promotion of Glycogen Synthesis (i.e. the removal of sugar from the blood for storage as larger sugar molecules in the liver and muscle): Insulin promotes the storage of glucose in the liver and muscle in the form of glycogen (lots of sugar molecules stuck together). After protein ingestion, insulin stimulates the uptake of glucose by liver and muscle cells and enhances glycogen synthesis. This helps regulate blood sugar levels and provides a readily available source of energy when needed.
3. Inhibition of Lipolysis (or the breakup of fat stores): this is key for the effects insulin has on weight loss and fat storage. Insulin inhibits lipolysis the breakdown of stored fat into fatty acids and glycerol. By reducing the release of fatty acids from fat storage sites and their uptake by the liver, insulin helps to prioritise the use of glucose as an energy source, especially after a meal rich in protein.
4. Stimulation of Protein Synthesis: While the primary site for protein synthesis is in muscle tissues, the liver also plays a role in protein metabolism. Insulin promotes the uptake of amino acids by the liver for protein synthesis and other metabolic processes.
5. Regulation of Metabolic Homeostasis: Overall, insulin plays a key role in maintaining metabolic homeostasis in response to protein ingestion. By coordinating the storage and utilization of nutrients, insulin helps ensure a balanced energy supply and demand, supporting various functions of the liver.
In conclusion, insulin's metabolic actions on the liver in response to protein ingestion involve regulating glucose production, promoting glycogen synthesis, inhibiting fat breakdown, supporting protein metabolism, and maintaining metabolic balance. These actions contribute to overall metabolic health and energy regulation in the body. Thus, protein metabolism and its actions are negatively effected when someone becomes insulin resistant as well as suffering from hyperinsulinemia (elevated blood insulin). The result of which can cause a reduction of fat release, increase in fat storage and heavier reliance on sugar for energy. Summary: 1) don't over eat protein, 2) eat protein from a whole food source 3) avoid drinking protein from a supplement source.
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