This clinical trial aims at assessing whether consumption of olive pomace oil in the diet may benefit persons with type 2 diabetes mellitus or persons at risk of developing the disease (prediabetic persons).
The main questions the study aims to answer are:
* May olive pomace oil prevent a high increase of blood glucose levels when consumed in a meal together with carbohydrates in diabetic/prediabetic patients? * May olive pomace oil decrease fasting blood glucose levels of diabetic/prediabetic patients after consuming it daily? * May daily consumption of olive pomace oil improve glucose homeostasis and other alterations like elevated blood lipids or inflammation, which also affect persons with diabetes or prediabetes?
Researchers will compare the effect of consuming olive pomace oil to the effects of a comparison oil (high-oleic acid sunflower oil).
Participants will:
In different days, they will consume white bread alone or the oils (olive pomace oil, high-oleic acid sunflower oil or extra virgin olive oil) spread on white bread and blood will be collected at different times during 2 h. This study to observe the increase of blood glucose after a carbohydrate-rich breakfast will be part of the so-called "postprandial" study, and will be conducted during 3 weeks, during which participants will consume corn oil on a daily basis.
Participants will also take part in the "chronic" study, that will last 22 weeks in total. During this study, they will firstly "wash" the effects of the oil they normally consume in their diets by consuming corn oil during 3 weeks. It is during these weeks when they will attend the Human Nutrition Unit (HNU) of ICTAN to carry on the "postprandial" study described in the previous paragraph.
After the initial 3 weeks, participants will consume olive pomace oil as the only oil in their diets during 8 weeks, "wash" its effects again by consuming corn oil during 3 weeks and then change to consume the other oil (high-oleic acid sunflower oil) during 8 weeks.
During the chronic study, they will visit the clinic once every 4 weeks for checkups and tests. They will refrain from eating other oils or specific fat-rich foods. Participants will also attend our phone calls to ask them what they ate the day before on different weeks during the study, and wear an accelerometer during 1 week to record their physical activity. They will keep a diary of the doses of insulin/metformin used and the blood glucose levels they measured at home.
Fasting blood glucose between 100-126 mg/dL and/or
Glycated haemoglobin (HbA1c) between 5.7-6.4% and/or
Diabetic persons with Fasting blood glucose >126 mg/dL and/or
Diabetic persons with Glycated haemoglobin (HbA1c) > 6.4%
Kidney or liver diseases
Gastrointestinal diseases (irritable bowel syndrome, Crohn disease, chronic bowel inflammation)
Food allergies/intolerances
Vegetarians/vegans
Crossover
Experimental arm: Olive pomace oil
Dietary supplementParticipants will consume during 8 weeks either the test oil (olive pomace oil) as the only dietary fat. They will consume 45 g/day of oil, using it in salads, fried foods, as spread on toasts, etc.
High-oleic acid sunflower oil
Dietary supplementParticipants will consume during 8 weeks either the test active comparator oil (high-oleic acid sunflower oil) as the only dietary fat. They will consume 45 g/day of oil, using it in salads, fried foods, as spread on toasts, etc.
Fasting blood glucose
Change of fasting blood glucose levels at the end of the chronic intervention
Postprandial blood glucose response
Change of postprandial blood glucose levels after consuming white bread with oil in comparison with white bread only. Blood will be collected at 0 h and 1 and 2 h after consuming the bread alone or with the corresponding oil. Olive pomace oil (active comparator) and high-oleic acid sunflower oil (active comparator) will be tested. Only in this postprandial study extra virgin olive oil will also be tested as a positive control (at the beginning of the run-in), along with white bread only (at week 2 of the run-in). Test/comparator oils will be assessed at the beginning of each arm, week 1 of each intervention arm (corresponding to weeks 4 and 14 of the study).
Insulin levels
Change in fasting blood insulin levels at the end of the chronic intervention
Insulin resistance
Change in homeostasis model assessment (HOMA) of insulin resistance (HOMA-IR) at the end of the chronic intervention
Insulin sensitivity
Change in quantitative insulin levels sensitivity check index (QUICKI) at the end of the chronic intervention. Higher score in QUICKI means a better outcome compared to initial values.
Glycated hemoglobin
Change in blood levels of glycated hemoglobin (HbA1c) at the end of the chronic intervention
Blood lipids
Change in serum levels of total cholesterol or LDL-cholesterol or HDL-cholesterol or triglycerides or apolipoprotein A1 or apolipoprotein B at the end of the chronic intervention
Inflammatory cytokines
Change in the levels of C-reactive protein (CRP), or pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-a), or interferon gamma (IFN-g), or interleukin (IL)-1beta (IL-1b), or IL-2, or IL-5, or IL-6, or IL-7, or IL-8, or IL-13)) or anti-inflammatory cytokines IL-4 or IL-10 at the end of the chronic intervention
Liver function
No changes in serum levels of alanine transferase (ALAT), or aspartate transferase (ASAT) or gamma-glutamyl transferase (GGT) at the end of the chronic intervention
Hormones, incretins and adipokines levels
Changes in serum levels of C peptide or glucagon or fibroblast growth factor 21 (FGF21) or glucagon inhibitory peptide (GIP) or glucagon-like peptide type 1 (GLP-1) or ghrelin or leptin or resistin or plasminogen activator inhibitor type 1 (PAI-1) or visfatin or adiponectin or adipsin or dipeptidyl peptidase IV (DPP IV) at the end of the chronic intervention
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Instituto de Ciencia y Tecnología de Alimentos y Nutrición
Lead sponsor
ICTAN-CSIC - Madrid - Spain
Collaborator
