The Effects of the MIND Diet on Oxidative Stress, Inflammation and Neurodegenerative Risk Biomarkers

American football is one of the contact sports with the highest risk in terms of exposure to repeated head impacts and the formation of neurodegenerative diseases that negatively affect the quality of life in the later stage of life. According to studies conducted in recent years, these athletes have a high risk of developing neurodegenerative diseases such as Alzheimer's, amyotrophic lateral sclerosis (ALS) and chronic traumatic encephalopathy (CTE) later in life. It has been reported that there are increases in the levels of oxidative stress, inflammation and neurodegenerative risk biomarkers and that some other biomarkers (such as BDNF, zonulin, telomere length, etc.) that may be associated with these may be adversely affected in American football players. It is necessary to develop new approaches to determine the preventive factors against the risk of neurodegenerative diseases that may occur in the later years of life due to contact sports such as American football. The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet has antioxidant (vitamins, flavonoids, phytosterols, minerals, terpenes and phenols) and anti-inflammatory (oleic acid, polyphenols and unsaturated fatty acids) properties that are thought to be effective in improving oxidative stress, inflammation and neurodegenerative risk biomarkers. The MIND diet can also reduce intestinal permeability with its abundant fiber content (prebiotic effect). It has been reported that the supplementation of some nutrients (docosahexaenoic acid, eicosapentaenoic acid, etc.) that have an important place in the composition of the MIND diet in this group of athletes has a positive effect on some of these biomarkers. However, the studies in the literature are limited, and there is no study involving the MIND diet in American football players. This study was planned considering that the MIND diet may have positive effects on oxidative stress, inflammation, and neurodegenerative risk biomarkers in American football players, who are exposed to repetitive head impacts as a nature of this contact sport.

American football players playing in the pro league will be included in this study. The sample size was calculated using the G*Power V. 3.1.9.6 program. This study will include two groups and two measurements. Accordingly, a total of 30 athletes, 15 in each group, with 95% confidence (1-α), 95% test power (1-β) and f=0.6 effect size; with 80% confidence (1-α), 80% test power (1-β) and f=0.6 effect size, a total of 20 athletes, 10 in each group, should be included.

At the beginning of the research, a face-to-face questionnaire will be used to question the athletes' American football history and player positions, socio-demographics, general health and nutritional habits. Before the start of the study, a 7-day food consumption record will be taken from the athletes. MIND scores will be questioned before the study and every week till the end of the study according to the frequency of food consumption in the MIND composition scale. It will be used to assess participants' adherence to the MIND diet. Accordingly, the MIND diet components include ten food groups (green leafy vegetables, other vegetables, nuts, berries, bean types, whole grains, seafood, poultry, olive oil, and wine) that are healthy for the brain. There are also five food groups (red meat, butter and margarine, cheese, pastries and sweets and fried / fast food / fast food) that are considered unhealthy. Frequencies of food consumption (daily, weekly, monthly) are questioned according to whether these 10 food groups specified in the template are preferred based on portion and meal or as primary, and as a result, scoring is made as 0, 0.5 and 1 points for each food group. The highest score is 15 points. Because the MIND diet template does not have specific scores for diet adherence, below the median score (7.5) will be considered low adherence. According to the MIND diet composition scale, those with a MIND diet score of <7.5 points will be included in the study, while those with a score of ≥7.5 will be excluded from the study. At the beginning of the study, body composition measurements (anthropometric measurements and bioelectrical impedance analysis) will be taken from the athletes along with the Pittsburgh sleep quality index scale scores, diet inflammatory index, and the World Health Organization quality of life scale-short form. Oxidative stress, inflammation, neurodegenerative risk and other associated biomarkers will be analyzed in blood samples.

Athletes will be randomized into two groups; MIND diet and control group. The players in the control group will sustain their habitual nutrition, while the current nutrition of the players in the MIND diet group will be adapted to the MIND diet according to the food groups in the MIND diet components and their consumption frequencies. In this context, the players will be informed about the general characteristics of the MIND diet and its importance in terms of their health. To help the participants in this regard, information will be given about the changes in the size and amount of foods and their portions in general with the "Meal and Food Photo Catalogue". As a result of the interviews with the coaches and experienced players, it was learned that the majority of the players did not consume/can't access the foods such as wine, berries, and fish included in the MIND diet template. Therefore, these foods, which are the main components of the MIND diet, will be provided by the researcher/project by the recommended frequencies. However, since wine consumption is not frequently preferred in our country due to religious and socio-cultural reasons, ''hardaliye'' (100 mL/day), which is easy to consume and has similar nutritional values to wine (resveratrol and ORAC), will be provided. Red forest fruits will be supplied in 2 portions/week, and fish (tons) in 1 portion/week. Before the study, participants assigned to the MIND diet group were provided with brochures, information, presentations, etc. so that they could adapt to the MIND diet. Participants in this group will be supported during the study period to increase their adherence to the MIND diet with information and suggestions via phone, mail, WhatsApp groups, etc. Those in the MIND diet group with an overall mean MIND score of <7.5 at mid- or end-of-study will be excluded from the study. Athletes in the control group with an overall mean MIND score of ≥7.5 at the mid- or end-of-study will be excluded from the study. Since all teams will participate in the same number of competitions and the group matches will last approximately nine weeks, the follow-up time has been determined as nine weeks. At the end of the nine-week follow-up, all parameters evaluated at the beginning of the study will be taken again, and the last values will be compared with the previous values.