OAT-GUT-BRAIN: Effects of Oats and Rice on Comprehensive Health of Metabolically Challenged Individuals

Serum total cholesterol will be measured from fasting blood samples at the baseline (week 0) and after 6 week of the dietary intervention (week 6).

Interleukin-10 is measured from fasting plasma samples at the baseline (week 0) and after the 6-week diet intervention (week 6). It will be analysed as part of the Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden) that provides absolute quantities for 45 different proteins, such as interleukins, interferons, chemokines and growth factors that are related to inflammation.

Cholesterols (HDL, LDL), Triglycerides and Free fatty acids (FFA) are measured from fasting blood samples before and after the 6-week dietary intervention.

Glucose and insulin are measured from fasting blood samples before and after the 6-week dietary intervention.

Glucose and insulin in blood is measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

Inflammation markers of 45 different proteins, such as interleukins, interferons, chemokines and growth factors are measured from fasting plasma samples at the baseline before and after the 6-week diet intervention. The absolute quantities of the markers will be analysed with Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden).

Circulating metabolites are measured from fasting plasma samples before and after the 6-week dietary intervention.

Circulating tryptophan metabolites are measured from fasting plasma samples before and after the 6-week dietary intervention to study modulation of the gut-brain-axis.

Blood samples are taken at the fasting state before and after the 6-week diet intervention. Plasma is analysed by using UHPLC-MS to see the changes in plasma SCFA concentrations.

PYY concentrations in blood are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

The antioxidant status of plasma will be analysed with commercial kits of Ferric Reducing Antioxidant Power (FRAP) and Oxygen Radical Absorbance Capacity (ORAC) from fasting blood samples before and after the 6-week dietary intervention.

Stool samples are collected from the participants at the baseline (week 0) and after the 6-week diet intervention (week 6), and the metagenome is sequenced from the extracted DNA by shotgun metagenomics by Novogene GmbH (Munich, Germany). Changes in fecal microbiome during the dietary intervention are investigated by changes in alpha and beta diversities, taxonomy and metabolical pathways.

Blood pressure (systolic and diastolic) is measured twice, with a 1-min break between measurements at the baseline (week 0) and after the 6-week diet intervention (week 6).

Weight (kg), height (cm), and waist circumference (cm) are measured after an overnight fast at the baseline (week 0) and after the 6-week diet intervention (week 6). BMI is calculated from the measured results.

Food records are collected from three consecutive weekdays and one weekend day at the baseline (week 0) and after the 6-week diet intervention (week 6). AivoDiet software (AivoDiet 2.2.0.0, Mashie, Malmö, Sweden) is used to calculate nutrient intake from the 4-day food records.

Diet quality is measured through validated Food Frequency Questionnaire (FFQ) by Leppälä et al. (2010, doi: 10.1177/1403494810382476) including questions regarding oat and rice intakes to evaluate compliance to the study diet. FFQ is collected at the baseline, after 3 weeks of the diet and in the end of the intervention (week 6).

The changes in bowel movement frequency and stool consistency are recorded using a defecation record with the 7-step Bristol stool chart for the same 4 days as the food record. Participant will record the time of the bowel movement and the dominant type of the stool. The Bristol types will be categorized as hard (types 1 and 2), normal (types 3, 4, and 5), or loose stools (types 6 and 7).

Gastrointestinal symptoms (self-reported) are measured by a Gastrointestinal Symptoms Rating Scale (GSRS) questionnaire at the baseline (week 0) and after the 6-week diet intervention (week 6). The GSRS results are rated according to the severity of a symptom and divided into subcategories of stomachache, bloating, flatulence, constipation, and diarrhea in addition to the total score. A higher score refers to more symptoms.

Perceived well-being (self-reported) is measured by a RAND-36 questionnaire, derived from the Short Form-36 Health Survey (SF-36) at the baseline (week 0) and after the 6-week diet intervention (week 6). The RAND-36 answers are rated according to the instructions for indices that are then divided into scales of physical and social functionality, role limitations caused by physical and emotional health problems, bodily pain, general health perception, vitality, and mental health in addition to the total score. A higher score refers to better perceived health.

Established and well-validated computerised neuropsychological tests to measure cognitive load will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the cognitive load (Serial Sevens Task) test.

Established and well-validated computerised neuropsychological tests to measure reaction time and attention will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the reaction time and attention (Color Word Stroop test) test.

Established and well-validated computerised neuropsychological tests to measure response control will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the response control (Cued Go/No-Go Task) test.

Inflammation markers of 45 different proteins, such as interleukins, interferons, chemokines and growth factors are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6). The absolute quantities of the markers will be analysed with Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden).

SCFAs in blood are measured during 3 hours (3 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

Circulating metabolites are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

The antioxidant capacity of plasma is measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6). Commercial kits of Ferric Reducing Antioxidant Power (FRAP) and Oxygen Radical Absorbance Capacity (ORAC) will be used.

Satiety related sensations are evaluated before and right after consuming the test meal and repetitively during 3 hours for 8 time points after the starting point of the consumption using 10 cm visual analogue scales (VAS) anchored with extremes (0 = not at all, 10 = extremely). The evaluated sensations are hunger, fullness, satiety, and desire to eat. The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

HRV is measured with Bittium Faros ECG Sensor that is attached with three electrodes to approx. 2 cm below the clavicles, about halfway of the bone horizontally (2 electrodes), as well as to the left at the bottom of the rib arch, approximately in the same vertical line with the upper electrode. HRV is measured through the full study day during the postprandial meal test and neuropsychological tests. The changed HRV is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).

Stool samples are collected from the participants at the baseline (week 0) and after the 6-week diet intervention (week 6), and the changes in fecal bile acids during the dietary intervention are investigated.