Diet plays an important role in relation to prevention of type 2 diabetes, cardiovascular disease and certain cancers. Studies have shown that diets with high whole-grain content could decrease the risk of these lifestyle related diseases and in Sweden the national dietary guidelines recommends whole-grain based instead of refined cereal products. It is, however, not clear whether whole-grain from wheat and rye share similar protective effects since there are large differences in amount and quality of dietary fibre and associated bioactive compounds. The aim of this study is to evaluate the impact of a wholegrain diet with low- or high lignan content on different cardiometabolic risk factors with the primary endpoint being blood glucose levels after 2h oral glucose tolerance test in men with metabolic syndrome or sign thereof.

The study will be conducted in a randomized, cross-over design (8 wk intervention periods). The lignan-rich diet will be based on whole-grain rye products whereas the control diet will be based on whole-grain wheat products with some added wheat bran. Both diets will provide similar amount of whole grain (g/d) and total dietary fiber content (but dietary fibre quality will be different). Although rye has high lignan content, the aim is to further increase the lignan intake half-way through the whole grain rye intervention period. This will allow us to distinguish the effect of lignans from the effect of whole grain rye as well as evaluating potential differences in effects on cardiometabolic risk factors between whole grain wheat and whole grain rye intake after 4-week consumption. The study design will also allow us to investigate the effects of a putative interaction between microbiome x lignan rich diet and its implication of metabolic risk factors.

Blood samples will be collected by trained nurses at screening, baseline, after 4 weeks and 8 weeks of first intervention period, after wash-out (8 weeks), and after 4 weeks and 8 weeks of the second intervention period.

At each examination day participants will arrive to the test laboratory for blood samples and an oral glucose tolerance test (OGTT) where participants will be given a drink with 75 g of glucose to consume within 10 minutes. Blood samples will be taken after 30, 60 and 120 minutes. Furthermore, participants will be instructed to complete one 3-day weighted food record and also to collect 24-h urine and a fecal sample at week 0, 4, 8, 16, 20 and 24.

Inclusion Criteria:

• BMI > 25 kg/m2
• waist circumference > 102 cm
• at least one of the following: blood pressure >130/85 mmHg, serum triglycerides ≥1.69 mmol/L; HDL cholesterol <1.04 mmol/L; or serum glucose ≥6.1 mmol/L

Exclusion Criteria:

• smokers
• antibiotic use past 6 months
• cancer diagnose (past 5 years) or other chronic disease diagnosis
• excessive alcohol consumption (>21 units/week)