Kefir Versus Milk on Time-Trial Performance in Masters Athletes (KVM)

Effect of Flavored Kefir Versus Flavored Milk on Time-Trial Performance in Endurance Master Athletes

The purpose of this study is to determine the effects of added probiotic cultures to a carbohydrate + protein recovery beverage compared to a similar recovery beverage without probiotic cultures, in its ability to impact endurance performance, perceived ratings of gastrointestinal symptoms and markers of inflammation and intestinal damage.

Study Overview

• Status: Completed
• Conditions: Exercise Performance; Gastrointestinal Complication; Aerobic Endurance
• Intervention / Treatment: Other: Water; Other: Flavored Kefir; Other: Flavored Milk

Detailed Description

In a randomized, crossover fashion, the investigators will assess changes in exercise performance, gastrointestinal symptom rating scale scores, as well as interleukin-6 and intestinal fatty-acid binding protein levels following consumption of either water, kefir or flavored milk.

• Study Type: Interventional
• Enrollment (Actual): 11
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Missouri
    • Saint Charles, Missouri, United States, 63301
      • Exercise and Performance Nutrition Laboratory

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Provide voluntary signed and dated informed consent.
• Be in good health as determined by medical history and routine blood chemistries.
• Normotensive (seated, resting systolic blood pressure < 140 mm Hg and diastolic blood pressure < 90 mm Hg. If the first measurement is slightly elevated above these limits, the subject will be given a brief (5 minute) rest period, and two more measurements will be taken. The average of all three measurements will be used to determine eligibility.
• Normal seated, resting heart rate (< 90 beats per minute).
• Age between 40 and 75 years of age
• Body Mass Index <30 kg/m2 or Body Fat <30% for females and <25% for males
• Performing aerobic exercise > 150 mins/week and training for at least 3 years
• Well-trained will be defined as athletes that meet two of the four following criteria: training frequency is 3-7 sessions/week; duration of training sessions is 60-240 min; training background is at least 3 y; race frequency is at least once a year.

Exclusion Criteria:

• Individuals currently diagnosed or being treated for any cardiac, respiratory, endocrine, psychiatric, musculoskeletal, renal, hepatic, neuromuscular or metabolic disease or disorder that in the judgement of the study participant's personal physician or research nurse that will preclude their safe participation or will contraindicate quality control over the collected data
• Individuals currently diagnosed with or are being treated for celiac disease, lactose intolerance, digestive insufficiencies or other gastrointestinal complications such as irritable bowel syndrome, ulcerative colitis, etc.

Alcohol consumption (more than 2 standard alcoholic drinks per day or more than 10 drinks per week) or drug abuse or dependence.

• Smokers or individuals who have quit smoking within the last 6 months
• Participants that are unwilling to refrain from caffeine, nicotine, and alcohol intake for 12 hours prior to each study visit.
• Known sensitivity to any ingredient in the test formulations as listed in the Nutrition Facts label.
• Individuals who are determined to be on a ketogenic diet.
• Individuals who are cognitively impaired and/or who are unable to give informed consent.
• Participants that are unwilling to refrain from taking biotin at a minimum of 72 hours before visit 3 through the end of the study due to potential interference with laboratory analyses.
• Individuals taking a medication known to impact digestive function or hormonal functions that may impact how our body digests, absorbs or metabolizes nutrients
• Individuals that are currently taking a probiotic or a dietary supplement that may impact digestive function or hormonal function that may impact how our body digests, absorbs or metabolizes nutrients
• Participants that are unwilling to refrain from fermented foods and yogurt, as well as maintain normal consumption levels of prebiotics throughout the study.
• Pregnant women, women trying to become pregnant, or nursing women.
• Individuals who indicate they are actively restricting calories or attempting to lose weight.
• Participants that are unwilling to keep their self-directed training protocols the same throughout the course of the study
• Participants that are unwilling to wear the same shoes and similar clothing for all testing visits.
• Individuals who participate in aerobic exercise < 2 days/week or have been aerobically training < 3 years
• Individuals that do not meet the criteria to be defined as well-trained
• Unwillingness to intake a supplement or follow the study protocol
• Any other condition which in the investigator's opinion may adversely affect the subject's ability to complete the study or its measures or which may pose a significant risk to the subject.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Water	Other: Water; 340 mL plain tap water consumed immediately following glycogen depleting exercise
Experimental: Flavored Kefir; 1% Lowfat Kefir manufactured by Lifeway Kefir and containing 18 g of CHO, 10 g of protein, and 2 g of fat	Other: Flavored Kefir; 320 mL kefir consumed immediately following glycogen depleting exercise
Active Comparator: Flavored Milk; 1% Lowfat Milk manufactured by Prairie Farms and containing 24 g of CHO, 8 g of protein, and 2.5 g of fat	Other: Flavored Milk; 240 mL flavored milk consumed immediately following glycogen depleting exercise

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Aerobic Performance Times	5 kilometer running time-trial on a curved, non-motorized treadmill	Through study completion, an average of 3 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood Interleukin-6	Blood interleukin-6 concentrations in response to intense exercise	Through study completion, an average of 3 weeks
Blood Intestinal fatty-acid binding protein	Blood Intestinal fatty-acid binding protein concentrations in response to intense exercise	Through study completion, an average of 3 weeks
Gastrointestinal Symptoms	Gastrointestinal Symptoms measured using the Gastrointestinal Symptoms Rating Scale (GSRS) in response to intense exercise. The scale asks 15 questions, and asks participants to rate their gastrointestinal symptoms on a 7 point scale with 0 being no discomfort at all and 7 being very severe discomfort. Lower total GSRS scores indicate a better outcome.	Through study completion, an average of 3 weeks

Collaborators and Investigators

• Sponsor: Lindenwood University
• Investigators: Principal Investigator: Chad M Kerksick, PhD, Lindenwood University

Study record dates

Study Major Dates

• Study Start (Actual): March 7, 2023
• Primary Completion (Actual): August 15, 2023
• Study Completion (Actual): August 15, 2023

Study Registration Dates

• First Submitted: November 16, 2023
• First Submitted That Met QC Criteria: December 8, 2023
• First Posted (Estimated): December 11, 2023

Study Record Updates

• Last Update Posted (Estimated): December 11, 2023
• Last Update Submitted That Met QC Criteria: December 8, 2023
• Last Verified: December 1, 2023

More Information

Terms related to this study

• Keywords: Milk; Aerobic Endurance; Exercise Performance; Gastrointestinal Symptoms; Kefir
• Other Study ID Numbers: IRB-23-71

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: The investigators do not plan to make IPD available to other researchers

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No