Claudia Villalobos
Studies conducted by scientists from the Instituto Politécnico Nacional (IPN) demonstrate that silymarin, the active substance in the medicinal plant Silybum marianum, commonly known as milk thistle, can be an important ally for sports. This is after trials in animal models showed that its antioxidant and anti-inflammatory properties contribute to improving physical performance and muscle hypertrophy (muscle mass increase).
Given the scientific evidence of the hepatoprotective effect of milk thistle and considering that intense physical activity increases the production of free radicals, the expert group from the Escuela Superior de Medicina (ESM), led by Dr. José Antonio Morales González, initiated research focused on evaluating the biological activity of silymarin.
"The increase in free radicals is proportional to the intensity of training. Studies have shown that by supplementing with this flavolignan, it is possible to reduce oxidation in the liver and protect it from cellular damage. This opens up prospects for the health of athletes since the proper functioning of this organ is essential for metabolic activity and detoxification of the body," said Dr. Morales González.
Naturally, the body has antioxidant defenses, but there comes a point when these are not able to balance the damage caused by free radicals, and this balance needs to be restored with natural elements, as in the case of silymarin.
To carry out the trials, which are part of the doctoral thesis of researcher Nancy Vargas Mendoza, the research team experimented with four groups of Wistar rats. The first group (control) was fed normally and remained sedentary. The second group received food, and water, and engaged in physical activity. The third group was given food, water, and vitamin C, and underwent training, while the last group ate and drank like the others and also took the silymarin supplement.
Except for the control group, the other three were conditioned for eight weeks on a treadmill, with an increase in exercise time, speed, and incline as the days passed. After that time, the experimental animals exercised continuously for one hour.
At the beginning of the ninth week, the researchers began a test of maximum endurance capacity for the rodents. One hour before physical activity, they began intragastric administration of vitamin C to the third group and silymarin to the fourth group.
"The experiment started for all four groups at a speed of 16 meters per minute (min); every 30 seconds, the speed increased by one meter (m). The test ended when the rat was exhausted and no longer ran continuously for 5 seconds," explained the Polytechnic specialist.
At the beginning of the adaptation, the sedentary group ran an average of 58 seconds, and at the end of eight weeks, their endurance was 50 seconds. Group 2 (with physical activity and no supplementation) started with 50 seconds and ended with two minutes. The animals administered vitamin C had an initial time of one minute, and their maximum effort at 8 weeks was almost three minutes. Meanwhile, the silymarin group started in the first week with one minute and their maximum endurance at the end was 4 minutes and 10 seconds.
The doctor affiliated with Level II of the National Researchers System (SNII) stated that the control group initially ran 9.70 meters and ended at 8.40 meters; group two ran 8.50 meters in the first week and 46 meters in the eighth week. When the experiment began, the rodents supplemented with vitamin C ran 10 meters, and in the last week, they ran 71 meters.
"With this test, we confirmed that vitamin C is good for improving physical performance, but silymarin surpasses its effect. We observed that the group of animals with this supplement initially ran 10 meters and ultimately ran 105 meters. These results were reported in two articles in prestigious international scientific journals," he explained.
After conducting a histological study on the animals, the polytechnic scientists confirmed another effect of silymarin. "We observed that this active substance favors muscular vascularization (veins increase in size, leading to greater blood pumping and irrigation of tissues), which prevents cell damage in muscles, heart, lungs, liver, and kidneys," said the ESM specialist.
Furthermore, it was determined that the increase in blood flow is synonymous with greater hypertrophy. In this case, the rats that received silymarin supplementation exhibited larger muscles, specifically in the quadriceps located in the leg.
Eosinophils are a type of white blood cells associated with inflammatory processes. Researchers recorded a higher presence of eosinophils in rodents that engaged in physical activity without supplementation, while the levels were lower in the animals that ingested the active substance under study, indicating a protective effect against inflammatory processes.
In the next stage, the research will focus on quantifying the levels of free radicals in the tissues of the rodents, as well as their antioxidant defenses (catalase, superoxide dismutase, glutathione reductase, and total antioxidant capacity) to understand their balance in the tissues. "Initially, our theory is that the combination of physical activity and silymarin generates high levels of antioxidant defenses and a low quantity of free radicals, or at least a proper balance of both."
Dr. Morales González reported that during the studies, they detected the presence of the transcription factor Nrf2 (Nuclear Factor Erythroid 2-related factor), which is essential in the expression of genes that protect the cell against oxidative stress, inflammation, promote proliferative processes, and inhibit apoptosis (cell death). "We will quantify it in the samples because we have the hypothesis that silymarin activates it," he pointed out.
Although further research is needed, the results so far are promising, and it is anticipated that in the medium term, all the scientific foundations will be available to initiate a clinical study and establish that silymarin offers prospects for a safe natural product to enhance the physical performance of athletes, as it does not produce side effects like those caused by the consumption of artificial substances (steroids, anabolic agents, stimulants, and diuretics, among others), which are often illicit.
Selección Gaceta Politécnica #166. (September 30th, 2023). IPN Imagen Institucional: Read the full magazine in Spanish here
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