Effects of Increased Greek Yogurt Consumption in Senior Adults

Participants

The proposed project will follow a randomized controlled parallel design over 8 weeks. A total of 60 senior adults (aged 55+ years; males and females) from the Brock Senior Fit program and Niagara area. All participants will provide written informed consent in order to be included in the study. Potential participants will complete a standardized Get Active screening questionnaire of the Canadian Society for Exercise Physiology. Participants will be excluded from the study if they are injured and unable to participate in classes, have an allergy to dairy foods/dairy protein or have been diagnosed with lactose intolerance.

Study Design and Procedures

Participants will be invited to participate in this 8-week study, with senior fit participants being randomly assigned into the control (NYEX) or the intervention exercising (GYEX) group and non-senior fit citizens from the Niagara community will be assigned to the intervention non-exercising group (GYNE).

Control (NYEX) Group: During the 8-weeks, participants will be instructed to follow their typical, habitual diet and exercise regimen.

Intervention Exercising (GYEX) Group: During the 8 weeks, participants will be instructed to follow their typical, habitual diet and exercise regimen. Participants will be asked to consume 2 servings/day (preferably morning and night) of 175 grams of commercially available GY (0% fat, flavoured, 130 calories, 17 grams protein, 225 grams calcium (e.g., OIKOS High Protein GY) for a total of 8 weeks. For their convenience, the participants will be provided with appropriate scoops to measure out 175 grams of GY per serving of the larger 650-gram commercially available, pre-packaged containers. Although it is recommended to consume the two servings morning and night, to increase ecological validity and strengthen the feasibility of the intervention, the timing of the servings will be flexible to facilitate daily routines and lifestyles. For the same reasons, the participants will be able to choose the flavour of their GY.

Intervention Non-Exercising (GYNE) Group: During the 8-weeks participants will be instructed to follow their typical habitual diet. Participants will be asked to consume 2 servings/day (preferably morning and night) of 175 grams of commercially available GY (0% fat, flavoured, 130 calories, 17 grams protein, 225 grams calcium; e.g., OIKOS High Protein GY) for a total of 8 weeks. For their convenience, the participants will be provided with appropriate scoops to measure out 175 grams of GY per serving of the larger 650-gram commercially available, pre-packaged containers. Although it is recommended to consume the two servings morning and night, to increase ecological validity and strengthen the feasibility of the intervention, the timing of the servings will be flexible to facilitate daily routines and lifestyles. For the same reasons, the participants will be able to choose the flavour of their GY.

At weeks 0 and 8 (the beginning and end of the study), all participants will complete a series of nutrition and activity questionnaires and have their body composition measured, and their fasted, resting morning blood collected. All participants will be instructed not to consume any food or liquids (except water, as needed) 8 hours before the time of their blood draw, not to exercise for 12 hours before the blood draw, and not to make any changes to their normal routines. These measurements will take place in the Applied Physiology Laboratory at Brock University by the same investigators.

Measurements

The following measurements will be collected at the beginning (week 0) and completion of the study (week 8).

Blood analysis: A total of 10 microliters (mL) of blood will be collected from an antecubital vein by a certified phlebotomist or registered nurse using a standardized venipuncture technique. All blood samples will be centrifuged for 10 minutes. Serum and plasma will be aliquoted into pre-labelled Eppendorf tubes and stored at -80°C until analysis. The serum concentrations of markers and regulators of bone remodelling will be analyzed in duplicate using ELISA kits for osteocalcin, amino-terminal propeptide of type I collagen (P1NP), and osteoprotegerin (OPG)) and bone resorption (C-telopeptides of type I collagen (CTX), sclerostin, receptor activator of nuclear factor kappa-Β ligand (RANKL), and parathyroid hormone (PTH). The plasma concentrations of inflammatory cytokines, including interleukin-6 (IL6), interleukin-10 (IL10), tumour necrosis factor-alpha (TNFα), insulin-like growth factor 1 (IGF1), irisin and brain-derived neurotrophic factor (BDNF), will be measured in triplicate using commercially available ELLA kits. Plasma analyses will be performed in-house at the Centre for Bone and Muscle Health at Brock University.

Body Composition: Body mass and body composition, including lean body mass (LBM), fat mass (FM), and relative body fat percent (%BF), will be measured using bioelectrical impedance analysis (BIA; InBody520 bioelectrical impedance analysis system (Biospace Co. Inc. Los Angeles, CA, USA) following standard procedures.

Dietary and Physical Activity Assessment: Participants' energy intake and expenditure, including dietary intake, as well as macronutrient, micronutrient, vitamin, and supplement intakes will be recorded at weeks 0 and 8 using a standardized Food Frequency and Activity Questionnaire (FFAQ). In addition, participants' nutrition knowledge will be assessed using the self-reported 97-item General and Sport-Specific Nutrition Knowledge Questionnaire (GeSNK) developed by Calella et al. (2017). The GeSNK encompasses 64 items assessing general and sport-specific nutrition knowledge, to explore knowledge regarding macro- and micronutrients in various food choices, awareness of diet-health associations, knowledge of fluid replacement, supplement intake, and food choices regarding sport recovery meals. As mentioned above, the GeSNK will be completed online along with the medical screening questions used to screen for inclusion criteria.

Sample size calculation

To our knowledge, no study has assessed the impact of dairy consumption on markers of bone metabolism and inflammation in male and female seniors. Using G*Power analysis for a repeated measures analysis of variance (3 intervention groups, 2 timepoints, sex as covariate), we calculated that a total sample size of n = 54 (i.e., 18 per intervention group) would be required to detect a medium effect of partial η2 = 0.06 with a power of (1-β) = 0.90, and a probability level of p = 0.05. Thus, the proposed total of 60 participants is more than adequate to detect significant effects and interactions, while allowing for a 20% attrition rate.