Updated: Jan 5
Low grade inflammation, a known risk factor for development of cardiovascular disease, has in several studies been shown to be reduced by consumption of whole grain rye products. A recent study from Chalmers has shown that this may be explained by changes to the bacteria in the gut.
The study showed the participants who consumed rye products for 12 weeks had a lower concentration of C-reactive protein, a common marker of inflammation, in their blood compared to participants who consumed refined wheat products. Furthermore, certain bacteria in the gut, that are known to affect inflammatory response, was reduced in the rye group. These results indicate the health effects of rye may in part be explained by the effect rye has on bacteria in the gut.
The 12th of September 2020, Adila Omar defended her doctoral thesis from Karolinska Institutet on ‘Dietary carbohydrate quality and health – focus on low-grade systemic inflammation and cardiometabolic risk factors´ . Image from: Chalmers University of Technology.
Dietary carbohydrate quality, characterized by content of whole grain (WG), dietary fiber, and sugars, is important for human health. Whole grain consumption and cereal fiber can reduce the risk of chronic disorders such as cardiovascular disease (CVD) and type 2 diabetes, an effect partly mediated by alterations in cardiometabolic risk factors and low-grade systemic inflammation. High-fructose or high-galactose diets may trigger pro-inflammatory and negative metabolic effects, but fermentable dietary fiber, e.g., fructooligosaccharides (FOS), may mitigate these effects. This thesis examined the effect of dietary carbohydrate quality, characterized by intake of specific WGs and sugars, on low-grade systemic inflammation and cardiometabolic risk factors. In particular, it evaluated: 1) associations between long-term WG rye or wheat intake and inflammatory, endothelial function, and CVD risk-related biomarkers; 2) alkylresorcinols (AR) in adipose tissue as potential biomarkers of long-term WG intake; 3) effects of WG/bran rye and refined wheat on inflammatory and endothelial function biomarkers in individuals with low-grade prostate cancer; and effects of high fructose and galactose intake, with or without added FOS, on 4) selected metabolic factors and inflammatory and gut permeability biomarkers; and 5) modulation of gut microbiota in rats.
Data and samples from two prospective cohort studies, Swedish Mammography Cohort-Clinical (SMC-C) (n=109) and Cohort of Swedish Men-Clinical (COSM-C) (n=149), were used to analyze associations between long-term WG intake and selected biomarkers of inflammation, ndothelial function, and metabolic factors. WG intake was assessed by food frequency questionnaires and using alkylresorcinols (AR) in plasma and adipose tissue as biomarkers. Combined WG rye and WG wheat intake was positively associated with cathepsin S, while total AR in plasma was inversely associated with endostatin (adjusted for age, sex, and BMI). Long-term WG rye intake was modestly correlated (r=0.31-0.41) with AR in adipose tissue, whereas WG wheat was poorly correlated (r=0.17-0.33) over 14 years for men and 17 years for women. The effect of WG/bran rye on selected inflammatory biomarkers was explored in a dietary intervention cross-over study of 17 men with low-grade prostate cancer. TNF-R2, e-selectin, and endostatin were significantly lower in these men after consumption of WG/bran rye products than consumption of refined wheat with added cellulose. In an animal study with rats (n=6/group and time point) fed a high-fructose or high-galactose diet, with/without added FOS, or three control diets for six or 12 weeks, the intervention diets affected several metabolic factors and gut integrity markers, but not inflammation biomarkers. High-fructose and high-galactose diets did not cause substantial changes in gut microbiota composition, but addition of FOS favored the genus Bifidobacterium. Gut microbiota was associated with several metabolic and inflammation biomarkers.
These results suggest that WG wheat and rye may have positive impacts on some inflammation biomarkers. Fructose and particularly galactose had adverse metabolic effects in rats, but no obvious effect on inflammation markers. Sugars did not markedly affect gut microbiota composition in rats.
Main supervisor:
Rikard Landberg, Professor, Department of Biology and Biological Engineering, Division of Food and Nutrition Science, Chalmers University of Technology.
Co-supervisors:
Professor Alicja Wolk, Karolinska Institutet Institute of Environmental Medicine Unit of cardiovascular and Nutrition Epidemiology
Associate Professor Galia Zamaratskaia Swedish University of Agricultural Sciences Department of Molecular Sciences
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