The 17th of September 2021, Kia Nöhr Iversen defended her doctoral thesis from Chalmers university of Technology on ‘High fiber rye foods decrease body weight and body fat and affect metabolic risk markers´. Image from: Chalmers University of Technology.
Overweight and obesity are major risk factors for development of non-communicable diseases, such as type-2 diabetes and cardiovascular disease, and increase the risk of early mortality. Diet and food consumption are among the most important factors in preventing and reversing overweight, obesity and their comorbidities. Whole grain has been associated with decreased risk of overweight and obesity in observational studies, but the results from interventions are inconsistent. This may be because very few interventions have been adequately designed for evaluation of the effects of whole grain on body weight management and these effects may differ between different whole grain sources. Rye is the cereal with the highest fiber content and has been suggested to be superior to wheat in inducing beneficial physiological effects with health implications, but large randomized controlled trials with well-characterized intervention foods are lacking.
The thesis by Kia Nöhr Iversen aimed to investigate the effects of rye-based cereals, compared with refined wheat-based cereals, on body weight loss and metabolic risk factors. Furthermore, the potential influence of subjective appetite and gut microbiota were investigated. High fiber rye-based cereal products were shown to induce greater reduction in body weight and body fat than corresponding refined wheat products after 6 and 12 weeks of intervention among overweight and obese men and women. No consistent effect of rye products on appetite response was found and the changes in body weight and body fat could not be linked to differences in subjective appetite or food intake. However, this may be due to methodological issues and warrants further research. Compared with refined wheat products, high fiber rye-based cereal products were shown to lower C-reactive protein, a marker of inflammation and a risk factor for cardiovascular disease, in two different populations. This effect was associated with reduction in abundance of certain bacteria in the gut that have previously been associated with decreased gut barrier integrity, suggesting that the effect of rye consumption on inflammation may, at least partly, be mediated through changes in gut microbiota composition and decreased gut permeability.
In conclusion, the work included in the thesis by Kia Nöhr Iversen suggests that replacing wheat-based cereals with high fiber rye-based cereals can aid the reduction of body weight and body fat, and reduce low-grade inflammation. These results can support the development of dietary guidelines and promote the development of healthier food products.
Main supervisor
Rikard Landberg, Chalmers University of Technology, Dept. Biology and Biological Engineering
Wholegrain rye may improve blood glucose regulation and blood lipid composition. The effects are hypothesized to be mediated through fermentable dietary fiber and lignans. In recent studies, the role of gut microbiota has been highlighted as a potential modifier of health effects of wholegrain intake.
In this study, several researchers from the Nordic Rye Forum were involved to investigate the effect of wholegrain rye (alone or supplemented by lignans) and wholegrain wheat diets on glucose tolerance and other cardiometabolic risk factors. Effects of the intervention diets were analyzed in relation to gut microbiota composition. The study subjects were men with higher risk of developing metabolic disorders, who during eight weeks consumed the rye (4 wks alone, 4 wks supplemented by lignans) or the wheat diets. After the eight week period, the diets were switched during eight more weeks; a so called cross-over setup, where the subjects serve as their own controls.
The effects on glucose metabolism were similar between the different wholegrain diets, irrespective of lignan supplementation. However, depending on variations in the subjects' gut microbiota, the both rye diets lowered LDL-cholesterol during a defined time-period compared with the wheat diet.
Kati Hanhineva is newly appointed professor in food development at the Department of Biochemistry, University of Turku. We welcome the university as a new member in the Nordic Rye Forum with a fresh interview of Kati and her research.
What is your main research interest and how did you get into the area?
I did my PhD within plant biotechnology and got fascinated by bioactive plant-made secondary metabolites, phytochemicals, at that time. When I moved to a post doc position to University of Eastern Finland (UEF), I started to look at phytochemicals from a bit different angle, namely what is their importance in terms of human health when we eat plant-based, phytochemical-rich food. I have stayed in this field my whole career, and the key reason is that I have always found it very intriguing to resolve the structures of nice molecules, and more recently also to study how our gut microbiota is modifying them.
What is new and what attracted you with the new position?
Actually, within this position I feel that I am a bit closer back to my roots, as there will be strong emphasis on the (plant-based) food development and analysis. This is also the key issue that attracted me in the position, as it is not every day that you can read a perfectly matching job description, especially in your own country, in professorship level.
Has there been any surprises or challenges along with changes in affiliation?
Surely changes always bring challenges, and the least one is not the logistics, as I am happy to be able to continue also leading my research group at UEF, as well as collaborate within the EU funded MarieCurie position at Chalmers. But all of these offer great, complementary possibilities for cutting edge science very much involving Nordic rye research, so despite intensive traveling, I am very excited for the new situation.
What value can you bring into the Nordic Rye Forum from this new position?
Naturally the position is ensuring that I can continue contributing to the Nordic Rye and whole grain research, but also, I hope I can widen up the network and bring in complementary expertise via the new position.
What is next in your nearest future?
Setting up the new research group, and planning the research activities, as well as lot of grant applications to be able to conduct the research
What do you hope to accomplish in a long-term perspective in your new position?
My current focus is leaning more and more towards the direction of the importance of gut microbiota, and I hope that I can widen up our understanding in the area, especially when it comes to the healthy Nordic diet. Understanding the metabolic relationship would help us to develop food products that can modulate the gut flora in beneficial directions for our health.
What would you do with a € 1 000 000 grant – if it was handed to you today?
I would invest in a brand-new mass-spectrometer, an instrument that can measure very small compounds. The rest would go to the research of the importance of not only gut bacteria fermentation, but also the step before it - food fermentation – like the good old sourdough fermentation of rye for example!