Glycemic Index (GI) and Protein Nutrition: Choose low-GI foods and utilize amino acid complementarity to enhance nutritional value.

Blood glucose refers to the glucose in the blood. The main source of blood glucose is food, especially carbohydrates. After digestion and absorption, carbohydrates enter the bloodstream to provide the body with usable glucose. In healthy individuals, blood glucose levels remain relatively stable. After eating, blood glucose rises, stimulating the pancreas to secrete insulin, which prevents excessive increases in blood glucose. Two hours after a meal, blood glucose levels return to pre-meal levels. The rate and magnitude of the post-meal blood glucose rise are related to the food consumed. Different foods have different effects on blood glucose.

In 1981, Jenkins proposed using an index called the Glycemic Index (GI) to measure how much a food raises blood sugar levels after a meal. The GI measures the level of blood sugar response caused by consuming a particular food. Some foods, such as refined white rice and high-gluten flour buns, are easily digested and absorbed in the gastrointestinal tract, and the glucose released from their breakdown quickly enters the bloodstream, causing a rapid rise in blood sugar. These foods have a high GI value.

Other foods, such as whole grains and mixed grains, are high in dietary fiber, which is digested and absorbed more slowly. They stay in the gastrointestinal tract longer, resulting in a slower release of glucose and a lower peak blood glucose level, leading to a more gradual blood sugar response. These foods have a low glycemic index (GI). The GI can be used as a reference for food selection. Eating low-GI foods results in a gradual rise in post-meal blood sugar, preventing a large secretion of insulin and requiring only a small amount of insulin to control blood sugar within the normal range.

Consuming high-GI foods causes a rapid rise in blood sugar, stimulating a large secretion of insulin. This is not only detrimental to blood sugar control in diabetic patients, but also damages blood vessels due to persistently high insulin levels. Protein. Protein is an essential component of human tissues and organs; muscles and internal organs contain large amounts of protein. Protein plays vital physiological functions in the human body. The amino acids that make up proteins can be arranged in different ways to form thousands of different proteins with varying functions.

(I) The building blocks of proteins

Proteins are composed of many amino acids linked together. Both human proteins and food proteins are composed of approximately 20 different amino acids. One amino acid can be converted into another through metabolic pathways in the body, or it can be synthesized from the metabolic products of carbohydrates and fats. However, there are nine essential amino acids that the human body cannot produce, or cannot produce at a rate sufficient to meet its needs, and must be obtained from food. These nine amino acids are called essential amino acids: tryptophan, lysine, phenylalanine, methionine, threonine, leucine, isoleucine, valine, and histidine.

(II) Physiological functions of proteins

1. Protein is an essential component of human tissues and organs. Human muscles, internal organs, and even bones and teeth contain large amounts of protein. Children and adolescents need to constantly synthesize proteins for growth and development, and adults also need to continuously renew their body's proteins; all of this requires sufficient protein intake from food daily. 2. Protein constitutes various physiologically active substances in the body. For example, hemoglobin carries and transports oxygen throughout the body, enzyme proteins aid in digestion and absorption, and immune proteins maintain the body's immune function.

3. Maintaining fluid balance. Proteins in the blood regulate osmotic pressure, attracting fluid and retaining it in the blood vessels. If protein intake is insufficient, the protein content in the blood decreases, causing a large amount of fluid to accumulate in the intercellular spaces outside the blood vessels, resulting in edema. 4. Providing energy. Each gram of protein produces 4 kilocalories of energy through oxidation and breakdown in the body. Dietary protein typically provides 10% to 20% of the total energy intake.

(III) Nutritional value of food protein

Different types of proteins and proteins from different foods have different nutritional values. One factor is how easily the protein is digested and absorbed in the body. Another factor is its amino acid composition; the closer the amino acid composition of a food protein is to that of human protein, the higher its utilization rate. For example, animal-derived proteins such as milk, eggs, and beef are more efficiently utilized than plant-derived proteins such as wheat and rice. The nutritional value of protein is also limited by the deficiency of the one of the nine essential amino acids. For example, lysine in grains is the weakest link. To improve this, grains should be eaten with foods high in lysine, such as meat, eggs, milk, and beans, to achieve amino acid complementarity, which will greatly improve the nutritional value of the ingested protein.