What are the health benefits of wheat arabinoxylans?
Wheat arabinoxylans are a type of non-starch polysaccharide found in the cell walls of wheat grains. The interest in these molecules has been increasing over time due to their proven health benefits. The consumption of wheat arabinoxylans results in a strong prebiotic effect, enhancement in overall gut health and immunity, and improvement in metabolic parameters such as blood glucose and insulin levels.
What are arabinoxylans?
Arabinoxylans are a type of non-starch polysaccharide found in the cell walls of cereal grains. Arabinoxylans have been identified in all major cereal grains, including wheat, barley, oats, rye, rice, sorghum, maize, and millet. They are mainly localized in the cell walls of starchy endosperm, the aleurone layer, the bran, and the husk.
Not all arabinoxylans are the same. Depending on the cereal, arabinoxylans vary in amount and structure. Wheat arabinoxylans consist of side chains linked by α-(1→2) and/or α-(1→3) bonds along the xylan backbone, and xyloses are most commonly mono-substituted.
Furthermore, the molecular structure of arabinoxylans depends on the extraction method applied. Arabinoxylans are extracted using chemical, enzymatic, or physical treatments. The different extraction techniques result in differences in the degree of polymerization (which represents the length of the arabinoxylan chains), and the content of soluble arabinoxylan.
As with all dietary fibres, their physicochemical characteristics affect the degree to which the gut microbiota utilise them. Higher degrees of polymerization and concentrations of soluble fibre relate to greater bifidogenic effects [1].
Wheat arabinoxylans can be used as a dietary supplement due to their beneficial effects on gut health, glycaemic control and immune health.
Moreover, due to the physicochemical and technological properties of these molecules (e.g. water-binding capacity, gelation), wheat arabinoxylans are also used as a baking additive to improve dough consistency, increase loaf volumes and improve crumb structure.
The health benefits of wheat arabinoxylans
Research around wheat arabinoxylans suggests that these compounds, as part of dietary fibre, have many beneficial physiological effects along the entire human gastrointestinal tract.
These effects depend on a complex mixture of molecular and physical properties of arabinoxylan preparations, as well as on the site, rate and extent of their digestion and fermentation in the gut.
Wheat arabinoxylans have strong prebiotic properties
Arabinoxylans have strong prebiotic properties, by selectively stimulating the growth of beneficial bacteria in the colon, such as Bifidobacterium and Bacteroides species [2,3].
This change in the microbiota is associated with positive health outcomes, such as improved overall health, decreased gut infections and enhanced mineral absorption.
Additionally, intestinal bacteria ferment the prebiotics resulting in the production of short-chain fatty acids (SCFAs), which have numerous favourable effects.
These effects include the inhibition of harmful bacteria, colon cancer prevention or improvement of glucose tolerance, among others [4].
Wheat arabinoxylans improve glycaemic control and insulin sensitivity
Evidence suggests that wheat arabinoxylans improve metabolic control in people with impaired glucose tolerance and with diabetes type 2, by improving blood glucose and insulin levels [5].
In addition, the gut microbiota metabolize arabinoxylans, primarily producing the SCFAs butyrate, acetate and propionate. Acetate and propionate can bind to a specific protein receptor called GPCR43 in the colon.
After binding, the secretion of two peptides (PYY and GLP-1) is increased. This leads to lowered intestinal motility and decreased levels of a hunger hormone called ghrelin. These processes are key to improving glucose handling [6].
Moreover, the European Food Safety Authority (EFSA) concluded there is sufficient scientific evidence to substantiate the health claim that consuming arabinoxylans produced from wheat endosperm contributes to reducing glucose rise after a meal [7].
Nevertheless, some other soluble fibres have also associated health benefits; however, one of the advantages of arabinoxylans lies in their higher palatability.
Wheat arabinoxylans boost immune health
Arabinoxylans have immunomodulatory properties. Specifically, they enhance adaptive immunity, innate immunity and gut barrier integrity:
1. Adaptive immunity. Arabinoxylans increase vaccination efficacy against influenza, resulting in fewer adverse events, fewer respiratory tract infections and an improved seroprotection rate [8].
2. Innate immunity. As mentioned, arabinoxylans promote a beneficial SCFA profile. This leads to increased cytokine production, improved monocyte recruitment capacity, and activation of regulatory T-cells, resulting in increased immune system vigilance [9,10]. All these cells are involved in keeping the immune system in check by making sure that it returns to a stable state after invaders have been successfully cleaned up.
3. Gut barrier integrity. The SCFA butyrate provides additional energy to the gut cells and strengthens the mucus layer. Arabinoxylans further induce the upregulation of tight junction proteins, protecting the human body against foreign invaders and strengthening the immune system [11,12].
How can you add wheat arabinoxylans to your diet?
Though in small concentrations, wheat arabinoxylans naturally occur in wheat-based products. However, if you want to increase the intake of these compounds in your diet, dietary supplements or enriched functional foods are also available. They are found in capsule form, in powder blends, bars and even products such as enriched bread, pasta, and a variety of other snacks.
Generally, consuming 1 to 5 grams of arabinoxylans daily is enough to benefit from their prebiotic effect. Regarding EFSA’s health claim on glycaemic control, at least 8% of arabinoxylan-rich fibre produced from wheat endosperm per unit of available carbohydrates should be consumed.
Wheat arabinoxylans are generally considered safe and well tolerated by the gut, meaning that they do not cause intestinal discomfort [13,14].
