The aim of this study is to investigate the effects of dietary plant and animal proteins on gut metabolism and markers for colorectal cancer as well as blood protein metabolites and markers for type 2 diabetes in healthy adults. The study participants will be stratified into three groups with different protein composition in diets: 1) animal 70%/plant 30%; 2) animal 50%/plant 50% and 3) animal 30%/plant 70%. The participants will get part of their diet as ready foods or raw material to promote their compliance. The participants will also get personal advice for their diets. Blood, stool and urine samples will be collected in the beginning and in the end of the 12 week intervention, as well as phenotype measures like BMI, blood pressure and body composition. The participants will also fill food diary before and in the end of the intervention.

A human intervention study with healthy volunteers will be carried out to compare the effects of animal and plant-based protein sources on gut metabolism and markers for colorectal cancer as well as blood protein metabolites and markers for type 2 diabetes.

The study will be done in parallel-design, randomized fashion, with healthy human volunteers aged 20 - 69 years. Exclusion criteria will be as follows: strict vegan, regular user of fish oil or other food supplements, extreme sports, inflammatory bowel disease, colon irritable, celiac disease, continuous antibiotics or less than three months of the latest antibiotics use, type 2 diabetes and hormonal, liver or kidney disease. Duration of the intervention will be 12 weeks.

Intervention groups will be as follows (n=50/group):

Group 1: Dietary proteins from animal sources 70% and from plant sources 30%, representing an average Finnish diet consumed at the moment.

Group 2: Dietary proteins from animal sources 50% and from plant sources 50%, containing at most 500 g red meat/week (according to the current Finnish Nutrition Recommendations).

Group 3: Dietary proteins from animal sources 30% and from plant sources 70%.

The intake of total protein will be kept at similar level compared to habitual, but intakes of fat and carbohydrates may vary as composing a diet with plant-based protein sources inevitably causes changes for example in dietary fibre intake. We will aim at controlling other potential dietary confounders to the extent that is possible in a whole-diet approach. This will ensure the feasibility of the diets and facilitate future applications in dietary practices at the population level.

Before starting the intervention, the persons will get dietary advice how to fulfill their diets. They will get part of foods free to help to implement the diets and to enhance compliance.

Blood, urine and fecal samples will be collected at the baseline (at the beginning of the intervention) and at the end of the intervention. Dietary intake and food consumption during the intervention will be followed by 3-day food records in the beginning and at the end of the intervention period. Nutrient intakes will be calculated using AIVO program.

The following data collection and analyses will be carried out at the beginning and at the end of intervention:

• height, weight, waist circumference
• body composition by bioelectrical impedance analysis
• resting blood pressure, hemoglobin
• fasting lipid profile in the blood (total cholesterol, LDL and HDL, triglycerides)
• fasting glucose and insulin, HbA1c in the blood
• markers for low-grade inflammation in the blood: hs-CRP, cytokines such as IL-1beta, IL-6, IL-10
• protein metabolomics in the blood
• markers of nutritional status in the bood: vit. D25-OH, carotenoids, vitamin C and B12, alkyl resorcinols
• urea/nitrogen in the urine
• measures of gut metabolism and risk markers for colorectal cancer: total N-nitroso compounds in the feces, plant-derived polyphenol metabolites in the feces, concentration of bile acids, cytotoxicity and genotoxicity assays of fecal water samples in 2D and 3D colon cancer cell cultures and gut microbiota analyses.

Inclusion Criteria:

Healthy, no exclusion criteria listed below.

Exclusion Criteria:

Strict vegan, food allergies, oral medication for any allergies, regular use of food supplements, extreme sports, inflammatory bowel disease, colon irritable, caeliac disease, any kind of cancer within 5 years, continuous antibiotics or less than three months of the latest antibiotics use, type 1 or 2 diabetes, hormonal, liver or kidney disease, pregnancy, lactation.