The goal of this controlled feeding trial is to learn about the metabolism of polyphenols, a common class of compounds found in plant-based foods, by the gut microbiome. It will evaluate how differences in gut bacteria across individuals influence metabolism of polyphenols from foods, which may influence health benefits that people receive from different foods.

This is a randomized, cross-over controlled feeding trial. Thirty healthy adult volunteers will be selected to participate on the basis of urinary screening results measuring a gut bacterial metabolite that is produced following consumption of a soy food: 15 O-desmethylangolensin (ODMA) producers and 15 age and gender-matched ODMA non-producers will be included. Participants will be assigned to consume two diets in random order: an apple catechin diet that provides a controlled amount of catechins in apple juice, and a nutritionally-matched low catechin diet. Both diet phases will last 3 days, with a 10 day washout period in between the two diet phases.

Inclusion Criteria:

1. Completion of informed consent.
2. Stated willingness to comply with all study procedures and availability for the duration of the study.
3. Any gender identification, aged 18 - 45.
4. BMI 18.5 - 40 kg/m^2
5. Ability to consume the intervention foods and beverages and be willing to adhere to the dietary regimen.
6. Agreement to provide urine and fecal samples according to the study protocol.
7. Agreement to adhere to avoid high catechin foods (tea, chocolate) for 4 weeks.
8. Able to come to the study location for 8 visits according to the study schedule.
9. As assessed through an initial urine screening phase, a person is eligible either on the basis of (1) the presence of a urinary marker for soy isoflavone metabolism (ODMA), or (2) as a control matched for age and gender.

Exclusion Criteria:

1. Current, regular use of antacids or acid reducers.
2. Systemic antibiotic use within the past month prior to the urinary screening until completion of the dietary intervention.
3. Pregnancy or lactation, within 3 months post-partum (regardless of breastfeeding) at screening or planning to become pregnant during the study duration.
4. Known allergic reactions to components of the foods or beverages of the study diet (soy, wheat, dairy, peanut, tree nuts, apples, eggs) or any history of anaphylactic food allergy.
5. Current diagnosis of renal, hepatic, or gastrointestinal conditions.
6. History of stroke.
7. Underweight (BMI <18.5 kg/m^2) or severe obesity (BMI >40 kg/m^2).
8. Under 18 years or above 45 years of age.
9. Unwilling or unable to participate in the controlled dietary intervention or provide urine or fecal samples.
10. Has a pacemaker, implanted defibrillator, or other implanted electronic device.
11. Change of body weight >10% between screening and dietary intervention.

During the crossover trial of two diets, participants will receive the same foods during both arms. The intervention and control will be delivered by a beverage containing either the active component or a nutritionally equivalent control beverage with similar flavor. Participants will not be told the order of study arms they receive. Drinks will be labeled with a code by a different researcher than the team interacting with participants. The statistician will not know which code corresponds to which intervention until analysis is complete.