A plant-based diet and its relationship with oxidative biomarkers in footballers

In a recent study published in Scientific Reports, researchers investigated the association between plant-based diets and oxidative biomarkers by calculating the plant-based diet index score and determining the levels of urinary biomarkers for oxidative stress in professional footballers.

Background

The accumulation of reactive oxygen species in the body leads to the damage of protein, lipids, and deoxyribonucleic acid (DNA), which is known as oxidative stress. The concentrations of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and F_2alpha-isoprostane (F_2a-IP) in urine have often been used as markers of oxidative stress. Diets that are largely plant-based have been thought to reduce oxidative stress and protect against reactive oxygen species.

Plant-based diets are also becoming increasingly popular, especially among athletes who have high energy and endurance requirements. These diets are categorized based on the proportion of plant to animal-based components in the diet. They range from completely plant-based, such as vegan diets, to semi-vegetarian diets that include some animal-based components.

Given that football is a sport that consists of activities such as intense bursts of running, jumps, and sprints that require high energy levels, adherence to nutritional diets is vital to the performance of footballers. They provide an ideal group to investigate how plant-based diets are associated with oxidative stress.

About the study

In the present study, the researchers compared the levels of urinary biomarkers F_2a-IP and 8-OHdG and the plant-based diet index scores between professional male footballers and matched non-athlete controls to examine whether plant-based diets were associated with decreased oxidative stress.

Footballers who had at least two years of professional experience and had strict training schedules were included in the study if their metabolic equivalent of the task was greater than 3000 minutes per week. They were also required to be non-smokers and not consume alcohol or take any antioxidant supplements. Healthy males with matched ages and body mass index (BMI) measures who had a metabolic equivalent of task between 600 and 3000 minutes per week were included as controls.

Interviews were conducted to determine the medical history, food intake data, physical activity levels, and general information on nutrition from all the participants. Anthropometric measurements such as height and weight were measured to calculate the BMI, and urine samples were obtained to measure the oxidative stress biomarker levels. A questionnaire was also used to determine physical activity levels.

A semi-quantitative food-frequency questionnaire was used to determine the food intake of all the participants over the previous year, including the consumption of specific items being determined in terms of grams per day. The plant-based diet index score was calculated using this information, and the results were used to classify the diets into three major groups — healthy plant foods, less healthy plant foods, and animal foods.

The healthy plant foods diets consisted of vegetables, fruits, nuts, whole grains, legumes, coffee, tea, and vegetable oils, while the less healthy plant food diets consisted more of refined grains and sugar-sweetened beverages and desserts. The diets that were predominantly animal food-based consisted mainly of meat, eggs, seafood, fish, dairy, and animal fat.

Results

The results showed that the plant-based diet index score of the footballers was significantly higher than that of the matched non-athlete controls, but the healthy and unhealthy plant-based diet index scores that were separately calculated based on the diet groups were not significantly different for the footballers and non-athletes.

Furthermore, plant-based diets were found to be linked to lower levels of the oxidative stress biomarker F_2a-IP in the urine samples of all participants, indicating improved antioxidant status due to plant-based diets. Compared to non-athletes, footballers were also found to be more adherent to plant-based diets, as hypothesized by the researchers.

Footballers were found to consume more vegetables, fruits, legumes, and nuts than non-athletes, while the consumption of total and animal fats was lower among footballers than non-athletes.

The researchers also discussed the potential role of antioxidants and polyphenols present in plant-based diets in lowering oxidative stress. They also discussed findings from other studies that found inverse associations between F_2a-IP concentrations and vegetable components such as lycopene, beta-carotene, and lutein, suggesting that diets rich in vegetables lower oxidative stress.

Furthermore, dietary fats are known to increase the production of F_2a-IP and influence the concentrations of F_2a-IP transporters in plasma, which could potentially explain why diets low in dietary fats were associated with lower F_2a-IP levels in the urine.

Conclusions

Overall, the results suggested that adherence to plant-based diets among footballers was linked to lower levels of the oxidative stress biomarker F_2a-IP in urine. Additionally, the plant-based diet scores also showed that footballers were more likely to adhere to nutritional plant-based diets than non-athletes.