The various nutrients required by the human body must be continuously supplied and supplemented through food. So, what exactly should we eat? This involves the proportional relationship of food, that is, establishing a balanced relationship between the body's physiological needs and dietary nutrient supply, which is the concept of "dietary balance."
A balanced diet refers to establishing a balanced relationship between dietary nutrient supply and physiological needs in four aspects simultaneously. Namely: amino acid balance, energy nutrient composition balance, acid-base balance, and balance among the intake amounts of various nutrients. Only in this way can it be beneficial to the absorption and utilization of nutrients. If this relationship is disrupted, that is, if the diet does not meet the body's physiological needs, it will have adverse effects on human health, and may even lead to certain nutritional diseases.
Amino Acid Balance
The nutritional value of food protein largely depends on the quantity and proportion of the 8 essential amino acids contained in the food. Only when the quantity and proportion are close to the body's needs can human tissue proteins be synthesized; otherwise, the utilization of protein in the food will be affected. The World Health Organization has proposed the proportion of the 8 essential amino acids required by the human body. The closer the proportion is to this, the higher the physiological value. When the physiological value approaches 100, that is, 100% is absorbed, it is called complete amino acid balance.
Food Protein Amino Acid Composition Score: Human milk 100, egg 100, milk 95, soybean 74, rice 67, peanut 65, millet 63, wheat 53, sesame 50.
Proteins that can achieve complete amino acid balance are called complete proteins. This standard can be used to score the amino acids of proteins in various foods. The amino acid proportions in human milk and eggs are extremely close to those of the human body, so they can be called amino acid-balanced foods.
However, most foods have an unbalanced amino acid composition, so their protein nutritional value is affected. For example, excessive leucine in corn affects the utilization of isoleucine; excessive arginine in millet affects the utilization of lysine. Therefore, a diet that is primarily plant-based should pay attention to the rational combination of foods to coordinate the imbalance in amino acid composition proportions. For example, mixing grains with legumes to make soybean-corn flour, soybean-millet flour, etc., can improve the utilization rate and nutritional value of protein.
Energy Nutrient Composition Balance
Carbohydrates, fats, and proteins can all provide energy for the body, so they are called energy nutrients. When these three substances are taken in appropriately, their respective special functions can be brought into play and they can promote and protect each other. This situation is called energy nutrient composition balance.
The suitable ratio of intake for carbohydrates, proteins, and fats is 6.5:1:0.7. After physiological combustion in the human body, they provide energy for the body as follows: carbohydrates account for 60%-70%, proteins account for 10%-15%, and fats account for 20%-25%. This is called energy nutrient balance; otherwise, adverse consequences may occur.
When the intake of carbohydrates in the diet is too high, the energy proportion will increase, disrupting the balance among the three, leading to obesity, increasing the burden on the digestive system and kidneys, and reducing the opportunity for intake of other nutrients; when the energy provided by fat in the diet is too high, it will cause obesity, high blood lipids, and heart disease; when the energy provided by protein is too high, it will affect the normal function of protein, cause protein consumption, and affect the nitrogen balance in the body. Conversely, when the energy supply from carbohydrates and fats is insufficient, the protective effect of protein will be weakened. The three are interrelated. Once an imbalance occurs, it will affect health.
Balance Among the Intake Amounts of Various Nutrients
The various nutrients we consume in our diet, within a certain period, should be kept within a range of no more than 10% deviation from the standard supply. This mutual ratio can be called the basic balance of nutrients.
Acid-Base Balance
Under normal conditions, due to its own buffering effect, the pH value of serum is generally maintained between 7.3 and 7.4. Consuming appropriate amounts of acidic and alkaline foods will maintain the acid-base balance of body fluids, but if foods are improperly matched, it will cause physiological acid-base imbalance.
Common acidic foods include: egg yolk, rice, chicken, eel, flour, carp, pork, beef, dried squid, beer, peanuts, etc.
Common alkaline foods include: kelp, spinach, watermelon, radish, tea, bananas, apples, strawberries, pumpkin, green beans, cucumbers, lotus root, etc.
When foods are improperly matched and the amount of acidic food in the diet exceeds the required amount, it leads to acidic blood, darker blood color, and increased viscosity. In severe cases, it can also cause acidosis; at the same time, it will increase the consumption of cations such as calcium, magnesium, and potassium in the body, causing calcium deficiency. This phenomenon is called an acidic constitution, which will affect health.