The Research on the Effect of the Food with Different Glycaemic Index and Glycaemic Load on the Immunity of Endurance Athletes.

For studying the effect of eating the food containing carbohydrates with different glycaemic index and glycaemic load 2 hours before athletics on the exercise tolerance and immune function, select 10 men long-distance endurance athletes, use not completely random balance repeated testing methods, randomized complete the three endurance tests. And each test interval is not less than seven days. The results suggest that there is no apparent effect of eating the food containing carbohydrates with different glycaemic index and glycaemic load 2 hours before athletics on the exercise tolerance and immune function. Compared with the glycaemic index and glycaemic load of food, the carbohydrate content of the diet before athletics may be the more important factor affecting the immune response in endurance sports.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Long, moderate-intensity sports cause fatigue. The main reason is the body glycogen depletion or lowering blood glucose concentration. Previous studies have shown that pre-exercise filling carbohydrate (CHO) can improve endurance exercise capacity subsequently [1]. Especially for longer than 90 minutes of exercise time, effect of moderate-intensity endurance exercise is more evident. The potential mechanism may be that CHO intake before exercise increases glycogen stores. Movement appears to save glycogen, and blood glucose levels remain stable oxidation state. However, the previous intake CHO mainly pure glucose, fructose or glucose polymers filled. This approach is not consistent with the practical application of training athletes [2]. Before exercise to optimize energy substances, mainly need to improve CHO reserves and stabilize uses it in motion. Because the body is too large energy consumption of materials, endurance sports usually to increase the body's glycogen reserves by ingestion of some containing CHO-rich foods [3], while increasing the body's own satiety. However, this approach ignores the differences between individuals for CHO-containing food absorption and digestion. And among the field of sports nutrition research in recent years, by controlling the glycaemic index, a method to adjust the CHO intake, better able to make sporting events before [4], during and after filling CHO-containing foods reach a more optimal level of athletes, coaches and Sports workers to provide better nutrition supplement ideas.

The rest of the paper is organized as follows. In Section 2, related knowledge is described in detail. In Section 3, experiments are presented and the results are discussed in Section 4. Finally, a conclusion is provided in Section 5.

DESCRIBED RELATED KNOWLEDGE IN DETAIL

For a long time, moderate-intensity endurance exercise, sugar and fat have become a major source of energy supply. In the body fat reserves is considerable, mainly in the form of triglyceride storage, equivalent to 60 times of the amount of glycogen stores in vivo. While so much body fat content, but the fat structure is more complex, rarely used as a source of energy for the energy metabolism of cells. So long, moderate-intensity exercise mainly uses sugar as the main material. When doing endurance exercise, energy substances will be excessive consumed. Usually not simply supply CHO. But add some containing CHO-rich foods to increase the body's glycogen reserves, increasing the body's own satiety. CHO foods contain a variety of nutrients [5]. Food digestion and absorption are significantly different, causing different glycaemic responses and insulin responses. The glycaemic index is a kind of a way for assessing the body digest and the extent of absorption by glycaemic response after eating food containing the CHO. This method has been gradually applied in the field of sports nutrition [6].

THE EFFECT OF CARBOHYDRATES ON THE IMMUNE SUPPRESSION CAUSED BY MOVEMENT

Compared with the control group and the low-carb diets, before exercise intake carbohydrate and before and after exercise supplementary in sugary drinks, there is a close relationship between the blood sugar concentration of the body's and immune function improvement.

Humble found that sugar for the normal function of lymphocytes and giant antibiotic has an important role, and in vitro cell culture, also found that strength by concanavalin stimulated proliferation of these cells rely on the body is beyond the physiological range of glucose concentrations. In the beginning stages of prolonged strenuous exercise, blood glucose concentrations remains at a quiet level. In the later stages of the movement, due to the decline of muscle and liver glycogen, athletes greatly depend on the body's blood sugar to provide energy. For some athletes, blood sugar could fall to 5mmol/L, causing the symptoms of low blood sugar. It may endanger macrophages and lymphocyte function. However, compared with the cyclists, the danger of impaired immune function of endurance athletes is low. This is because the blood sugar of cyclists is easily fall in the long campaign. Endurance athletes are not so easy to fall [7].

Glycemic Index

Concept of the glycaemic index is first proposed in 1981 by a Canadian nutritionist Jenkins. It arranges food by glycaemic response of the body after 2 hours of eating foods containing CHO. Its most prominent feature is to prevent the problem of absolute blood glucose response CHO-containing foods have a greater difference between the individuals. For some time, GI has played a pivotal role in clinical practice in diabetes control diet and obesity. In recent years, GI studies have gradually applied to the field of sports nutrition, providing a new way for the deployment of science diet athlete training and competition [8].

The method for calculating GI is that after the organism empty stomach for 12 hours, fasting, and eating 50 grams test food containing CHO, then calculate the ratio between the increase area under the glucose curve and the area in the glucose curve eating the same component reference food containing CHO, that’s:

SCHO is the area under the glucose curve. is the area in the glucose curve eating the same component reference food containing CHO. GI also usually reflects the digestion and absorption of CHO food. High GI food represents that CHO-containing food has a faster digestion and absorption capacity.

The main factors affecting food G workers are (4): (1) food components, including differences in monosaccharide components, such as glucose, fructose, galaxies; (2) nature of starch, amylose and amylopectin content and proportion; (3) starch interaction with other ingredients; (4) food processing methods, such as the degree of processing, starch gelatinization degree; (5) anti-nutritional factors in food. Such as photic acid, polyphenols and phospholipids, these substances can reduce digestion and absorption of protein and minerals.

The study found: the higher the degree of gelatinization, starch is more vulnerable hydrolysed by enzymes in the body (8), so that the GI value of food increased; the higher ratio of amylopectin and amylose in food, the higher the food's GI. These factors are more or less affecting the digestion and absorption of food, so will affect the GI of CHO food.

Data Statistics Methods

Variance is a measure the degree of deviation between random variables and its mathematical expectation (i.e. mean). The variance of a random variable X is its second central moment, the expected value of the squared deviation from the mean:

This definition encompasses random variables that are discrete, continuous, neither, or mixed. The variance can also be thought of as the covariance of a random variable with itself:

In many practical problems, studding the degree of deviation between random variables and mean is of great significance.

RESEARCH METHODS

Experimental Subjects

The subjects were 10 male professional endurance athletes of our school, where average age is 20.6, average height is 176.8, average weight is 68.2, and average BMI is 20.1. Subjects have engaged in endurance sports for more than 4 years, training four times a week, each time lasting more than one hour and per week of running a distance of 40 km. Before exercise, all subjects have no symptoms of infection, and in the six weeks before the experiment cannot take any medication, and two days before the official test are prohibited high-intensity exercise.

Experimental Procedures

After 10 to 12 hours fasting, in the first experiment, subjects were randomized to eat HH, LL or HL meal. Make glycogen depletion in the morning in the first day, in horizontal treadmill run 30min with the speed of 9 km/h, and run 30min with the speed of 12 km/h. At 12:00 have lunch, and at 18:00 have dinner.

Test Indicators

(1) General indicators: heart rate, body composition;

(2) Subjective judgment: subjective feeling;

(3) Respiratory metabolic indexes: maximal oxygen uptake, oxygen uptake;

(4) Immune parameters: white blood cells, lymphocytes, T lymphocyte subsets, monocytes, neutrophils counts and interleukin-6.

Table shows the experimental sample data of the test, which is circulating concentrations of leukocytes, neutrophils, lymphocytes, and monocytes.

Blood Collection

Subjects arrived at the laboratory, sitted 20min, and then inserted the indwelling needle into the forearm veins, collected venous blood of quiet levels. After ingestion of diet 15min, 30min, 45min, 60min, 90min and 120min, sports 20min, 40min and 60min, sports 5km, 10km, after exercise 60min and 120min, take fingertip blood, measure the blood glucose concentration.

COMPUTATIONAL RESULTS AND COMPARISONS

Compared with the previous exercise, with eatting three different diets, after 60 minutes exercise, lymphocyte proliferation was inhibited. And resume to basal levels at the end of the two hours exercise. There are no significant differences between the three conditions, as shown in Fig. ().

Fig. () shows that compared with the response of big ups and downs of blood glucose after eating food H-H, after eating food L-L blood sugar level is relatively stable throughout the experiment.

Known from Fig. (), when the athletes ingested HH meal 2h before exercise postprandial, glucose area is about 1.5 times the LL meal and HL meal.

In this study, the reaction of immune cells is consistent with previous reports in three dietary conditions: Exercise can improve blood leukocytes, neutrophils and lymphocytes concentration; Neutrophils and leukocytes increased can last several hours to recovery period; the lymphocyte will rapid decline in recovery period. Some studies show that changes in stress hormones and hemodynamic changes in immune cells which may be related to the exercise-induced. Both factors related to exercise intensity. In this study, three exercise intensity under three meal conditions are substantially the same. Therefore, in low-CHO (HL) conditions, blood immune cell counts obvious changes may be related to differences of hormone concentrations caused by movement energy supply differences. Most of these hormones come from the edge of the pool and the bone marrow. When recovery period two hours, a moderate correlation of neutrophils and serum cortisol may partly explain this speculation. However, compared with the other two conditions, due to less CHO content in HL dietary, the available CHO reserve is low. Thus, in the latter part of the movement and recovery, this may lead to the content of residual CHO in the digestive tract is inadequate [9, 10].

CONCLUSION

In this study, direct observant the influence of the GI and GL foods in endurance sports for immune function. The results showed that, compared with the low-CHO (HL), two hours before exercise, intake of high CHO (HH, LL) foods can reduce the inhibition of leukocyte, neutrophil and lymphocyte proliferation and reduces recovery immediately after exercise and proliferation amplitudes. Meanwhile, after the intake of high CHO sports, serum cortisol in two hours and recover faster after exercise. The lymphocyte proliferation test results under three conditions, no significant difference in diet.

On the other hand, the results suggest that there is no apparent effect of eating the food containing carbohydrates with different glycaemic index and glycaemic load 2 hours before athletics on the exercise tolerance and immune function. Compared with the glycaemic index and glycaemic load of food, the carbohydrate content of the diet before athletics may be the more important factor affecting the immune response in endurance sports.

Table 1.

Circulating concentrations of leukocytes, neutrophils, lymphocytes, and monocytes before, during, and after exercise in the H-H, L-L and H-L trials.

No	Pre-Ex	60min	10km	Post 60min	Post 120min
Leukocyte
H-L	10.5	15.2	18.2	14.6	13.4
L-L	10.9	15.7	19.0	13.8	13.0
H-H	11.2	15.5	18.6	14.4	13.8
Neutrophils
H-L	7.6	8.7	10.5	11.2	12.5
L-L	7.0	8.5	11.2	11.6	12.0
H-H	7.9	9.0	10.4	11.7	12.8
Lymphocytes
H-L	2.5	3.2	3.5	2.8	1.8
L-L	2.6	3.6	3.9	2.5	1.9
H-H	2.1	3.8	4.3	2.6	1.6
Moncytes
H-L	0.8	0.9	1.7	0.6	0.4
L-L	0.5	1.0	1.8	0.5	0.4
H-H	0.6	1.0	1.6	0.8	0.5