The proposed study will examine whether eating yogurt every day can improve brain and gut health in children. Prior research suggests that yogurt may support cognitive functions like self-control, but more studies are needed to confirm this. The study will follow 60 children from Central Pennsylvania, ages 8 to 10, who will be randomly assigned to drink either fruit juice (control group) or yogurt smoothies once or twice a day for four weeks.

Researchers will compare how different amounts of yogurt affect children's thinking skills (like memory and focus), brain activity, and gut bacteria. These changes will be measured through brain scans, computer-based thinking tasks, surveys, and stool samples. The study will also collect information about children's overall diet. The goal is to find out if yogurt can support healthy brain and gut development and to determine the right amount to include in a child's daily diet. Results will help guide future research on how nutrition supports children's health.

This study is a randomized, between group, dose-response study. Children will be randomly assigned to either receive the control (fruit juice) or a dosage of the experimental yogurt smoothie (1x versus 2x daily) for 4 weeks. Blinding will be established so that researchers do not know which group children are assigned to and families do not know which smoothie is expected to change outcomes. Children will be advised to minimize additional consumption of fermented dairy during the intervention (besides the yogurt provided).

Outcomes will be measured at 2 timepoints: immediately before and immediately following the exposure (2 laboratory visits). The visits will take place around 4 weeks apart. In each visit, child participants will undergo a series of tasks, including a Stop Signal Task (SST), a Flanker Task, the Wide Range Assessment of Memory and Learning (WRAML3), the Delis-Kaplan Executive Function System (D-KEFS), the Weschler Abbreviated Scale of Intelligence (WASI-II), and the N-back test. During the N-back test, participants will wear an fNIRS cap to measure and record localized brain activity. Skin carotenoid levels will also be measured using the Veggie Meter. Throughout each visit, the parent participant will complete a series of questionnaires that assess family demographics, home food security, child behavior and temperament, child executive function, family food behaviors, child pubertal development, and beverage consumption frequency. Between the two visits, along with the consumption of the juice or yogurt each day, child participants will complete a weekly food log survey. Parent participants will also complete weekly surveys that assess home food inventory, food and beverage consumption practices, and child behavior. Additionally, parent participants will be asked to collect a fecal sample from their child 1-7 nights before each visit with a provided fecal sample collection kit.

Inclusion Criteria:

• Children should be of good health, without presence of any metabolic, gastrointestinal, or developmental disorders (e.g., ADHD, autism, etc.).
• Children should not be taking medications that impact appetite or cognitive function.
• Children must be willing to consume and report liking the fermented dairy smoothie.
• Children should be between the ages of 7-9 years-old at enrollment.
• Children should speak English fluently.

Exclusion Criteria:

• They are not within the age requirements (< 7 years-old or > 9 years-old) at baseline.
• They have known emotional or cognitive delays, so that we can be assured that they understand the procedures.
• They do not speak English fluently.
• They have parentally reported medical problems that affect the digestive system or ability to eat yogurt (e.g., lactose intolerance, food allergies, Crohn's disease, Celiac disease, Esophagitis) and/or are taking a prescription medication that may affect appetite (e.g., Ritalin, methylphenidate, Adderall XR, Concerta, Vyvanse, etc.).
• They are not from families of rural communities (assessed by National Center for Education Statistics local classifications).
• Their parent is unable to attend the study visits.

In this study, Research Assistants (RAs) responsible for administering tasks and collecting data (e.g., behavioral assessments, fNIRS recordings) are blinded to group assignment.