Nutrition during exercise: The roles of carbohydrates, proteins, and vitamins

Food is the fuel for the human body, this biological machine.

People ingest energy-containing foods, which are then oxidized within cells using inhaled oxygen.

As a result of food oxidation, the necessary energy is released to sustain human survival and enable people to perform various activities.

Therefore, nutrition plays a very important role in exercise.

Exercise training requires energy, and the three major nutrients that supply energy to the human body are carbohydrates, fats, and proteins, among which carbohydrates are the most important.

1. Carbohydrates

Different foods contain varying amounts of sugar. Starchy foods are high in sugar, and the most common examples are foods made from rice, flour, sweet potatoes, and potatoes.

The average sugar content in these raw materials is around 70%.

Meat contains little sugar.

Based on the rate and magnitude of the increase in blood glucose levels after eating, foods and drinks can be classified into three categories: high, medium, and low glycemic index.

Foods with a high glycemic index include: bread, steamed buns, rice, cornflakes (or porridge), bananas, chocolate, boiled (or baked) potatoes, honey, glucose solution, sucrose solution, and maltodextrin; foods with a moderate glycemic index include: noodles, oatmeal porridge, potato strips, sweet potatoes, grapes (juice), and oranges (juice); foods with a low glycemic index include: fructose, ice cream, milk, yogurt, and tomato soup.

Carbohydrates have the following advantages as an energy source: they can be broken down in large quantities to provide energy, whether the muscles are well-oxygenated during exercise or when the muscles are relatively poorly oxygenated during heavy exercise; the energy produced by consuming the same amount of oxygen is higher than that produced by fat; the product of complete oxidation of carbohydrates is lactic acid, which can be used by the body to resynthesize glycogen or be re-oxidized.

Athletes, especially those engaged in high-intensity training, competitions, or endurance events, have an increased need for energy, which in turn increases their need for carbohydrates.

Foreign sports nutritionists recommend that, under the above conditions, the daily intake of carbohydrates should be 8-10 grams per kilogram of body weight, accounting for 60%-70% of the total energy.

An athlete weighing 70 kg needs 560-700 grams per day, which is equivalent to 0.7 kg of rice or a meal or pasta made from standard flour.

Based on the above, choosing the right foods is the most effective way for athletes to increase glycogen stores in the body before exercise, and an important method to increase muscle glycogen content before exercise and replenish glycogen consumed during exercise.

Eat more sugary foods such as pasta, rice, potatoes, and sweet potatoes in your daily life, and supplement with sugar 4 to 7 days before the competition (the specific method depends on the competition schedule).

2. Protein

High-protein foods are like building materials for human tissues.

Proteins are essential for the human body to build new cells and tissues during growth and development, and are used to replace some of the cells that are constantly damaged and aging.

Because of their different amino acid structures, there are many types of proteins, and plant proteins and animal proteins are not the same.

Human tissues need to ingest certain amino acids. Without these amino acids, a person cannot live healthily because the human body cannot synthesize them. These amino acids are called essential amino acids.

Poultry, fish, eggs, milk, and cheese contain proteins with appropriate amounts of essential amino acids.

These types of foods are the best sources of protein.

Adults need about 1 gram of adequate protein per kilogram of body weight per day.

An adult needs about 70 grams of protein per day.

Athletes need slightly more protein during high-intensity training, especially strength training.

Protein is a basic component of the human body. High-intensity training can cause a negative nitrogen balance and exercise-induced anemia in the body.

If an athlete's nutritional status remains unchanged, but the amount of exercise is increased, hemoglobin levels will decrease, urinary nitrogen excretion will increase significantly, and a negative nitrogen balance will occur.

Increasing protein intake during high-intensity training can help maintain hemoglobin levels and prevent exercise-induced anemia.

Therefore, athletes in their growth and development period should appropriately increase their protein intake if they experience weight loss in the early stages of exercise or when increasing the intensity of training.

3. Vitamins

When engaging in physical exercise, the body's metabolic processes are enhanced, increasing the need for vitamins.

Strenuous exercise can accelerate the onset of vitamin deficiencies.

An athlete's vitamin requirements are related to the amount of exercise, as well as their original physical function and nutritional status.

Early signs of vitamin deficiency in athletes often include decreased athletic performance, weakened immunity, and fatigue. Supplementing with vitamins at this time can improve these functions.

However, those with good nutritional status do not need to supplement with vitamins, especially excessive intake of a certain vitamin, which can cause an imbalance between some nutrients in the body.

Some fat-soluble vitamins can accumulate in the body, and excessive amounts can cause poisoning.

The vitamins that athletes often supplement include vitamin B₁, vitamin B₂, vitamin B6, vitamin C, vitamin E, vitamin A, and vitamin PP (niacin).

They play a beneficial role in human sugar metabolism, the breakdown and synthesis of acetylcholine, maintaining the body's energy metabolism, participating in the body's reduction processes, and enhancing the body's resistance to hypoxia.

Vitamins play an important role in the nutrition of athletes.

When using vitamins, attention should be paid to the appropriate ratio and antagonistic effects between various vitamins.

Vitamins and other nutrients in food, such as sugars and fats, should also be kept in appropriate proportions.

The proportions of various nutrients in natural foods are generally appropriate. Overemphasizing one type of food or using too much of a nutrient supplement can disrupt the proper proportions of various nutrients in the body.

Under good nutritional conditions, there is no need to supplement with vitamin preparations. However, during the winter and spring seasons when vegetables and fruits are scarce or during periods of increased exercise, it is appropriate to supplement with some multivitamins.

4. Fat

Fat has a small volume but a high calorie content, which helps reduce food intake and increase the body's ability to withstand cold.

Prolonged exercise increases the body's fat consumption, raises ketone levels in the liver and blood, accelerates the oxidation of ketones in the heart and skeletal muscles, inhibits glucose oxidation, and reduces the release of amino acids from muscles. Fat plays a role in conserving glycogen and protein in the body.

Fat is difficult to digest, and excessive consumption can reduce the absorption of other nutrients, especially protein, in the intestines.

Fat oxidation can increase the body's oxygen requirements.

Foods high in fat can affect appetite.

Hyperlipidemia slows blood flow, affecting the body's oxygen supply and hindering exercise.

In some anaerobic sports, a high-fat diet can increase the levels of ketoacids and lactic acid in the blood of athletes.

When athletes consume fats, they should try to use vegetable oils rich in unsaturated fatty acids, and the P/S ratio (unsaturated fatty acids/saturated fatty acids) of the fat should be greater than 1.

Only in this way can exercise be beneficial.

The calories and nutrients provided by the food consumed by athletes in their three meals should be in balance with the energy required to complete their daily exercise.

From a nutritional perspective, there should be sufficient energy, and the content and ratio of protein, fat, and carbohydrates should be appropriate, as well as sufficient inorganic salts, vitamins, trace elements, and water. In other words, the selection of various types and quantities of food each day should be appropriate and sufficient.

Some people experience muscle and joint soreness and fatigue after exercise and believe that eating more poultry, fish, and eggs can replenish nutrients and relieve fatigue.

In fact, this idea is a cognitive bias.

When the human body exercises, muscles and the brain work at high intensity, and large amounts of carbohydrates, fats, and proteins are broken down in order to ensure the body's energy needs during activity.

During the process of energy metabolism and decomposition, the body produces a large amount of acidic metabolic products such as lactic acid and phosphoric acid. These acidic metabolic products accumulate in tissues such as blood, muscles, brain, and internal organs, which can cause discomfort such as muscle and joint pain, fatigue, and weakness.

At this time, simply eating more acidic foods such as meat will aggravate the acidification of the blood, which is not conducive to the elimination of metabolic products and makes it difficult to relieve muscle soreness and fatigue.

To eliminate these discomforts, these metabolic "wastes" must be neutralized and excreted from the body. Therefore, it is advisable to eat more alkaline foods such as vegetables and fruits rich in vitamins and fiber to neutralize blood acidity, maintain blood slightly alkaline, promote the excretion of metabolic products, maintain the basic acid-base balance of the body, and restore normal physiological state as soon as possible.