Article written by guest expert Dr Talitha Best, Central Queensland University and adjunct Research Fellow at the University of South Australia with research and clinical interests in exploring the effects of diet and nutrition on cognition and well-being.
The brain is a complex organ that, like every other organ in the body, requires nutrition to support optimal function. Research is now showing that everyday mental functioning, such as mood, memory and cognitive performance, can be impacted by diet. More than just dietary fibre to help maintain healthy bowels, non-starch polysaccharides found in grains, plants and fungi may be dietary components that support brain health.
Just like non-resistant starches, non-starch polysaccharides (NSP) have an important role to play in health. Whilst the structural and functional properties of these NSP’s are diverse depending on the variety and source, it is clear that they play an important role in promoting better health outcomes. These include, lowering blood cholesterol, improving blood glucose regulation and insulin sensitivity, immune function, cardiovascular function, gastrointestinal structure and function, as well as prebiotic effects.1
A wide range of NSP such as arabinogalactans, arabinoxylans, and mixed beta glucans, found in many cereals, grains, legumes, plants and fungi, are emerging as functional dietary components. The application of these complex saccharide compounds to brain function is a new emerging area of research. Whilst there remains a large research gap in the understanding of the mechanisms by which these polysaccharides impact the brain, at present there are preliminary human studies that suggest a positive impact on neurocognitive function in humans.
Specifically, in a randomized controlled study, a group of 75 athletes were given barley derived mixed beta-glucan extract for 4 weeks and were assessed on mood outcomes. At the end of the study, compared to placebo, those that had received the 250mg or the 500 mg dose reported improved mood outcomes, as reduced tension, confusion and fatigue, and increased vigor.2 Similarly, an Australian study showed positive effects of an arabinogalactan and glucomannan plant derived blend of polysaccharides on cognitive and mood outcomes in middle-aged adults. This study showed that after 12 weeks, compared to placebo those that had received the 4g dose of NPS report improved mood outcomes, as reduced tension and improved outlook, and better memory recall.3 These emerging studies point to the potential of NPS’s to improve cognitive health.
The brain requires nutrition for optimal structure and cellular function. Emerging studies suggest that NSP’s have a direct impact on the electrical activity of the brain. Administration of NSP’s derived from lichens and barley, in animal models, shows that these complex polysaccharides increase the electrical activity of cells within the hippocampus, an area of the brain associated with learning and memory.4,5 These findings provide a clue about potential mechanisms that might underpin memory effects seen in human studies.
In addition, NPS effects on cognitive function may be through mechanisms related to cognition and mood, such as blood glucose regulation and gut function. Whilst a vast majority of NPS’s are considered indigestible by the human digestive tract, some are known to have prebiotic effects that could benefit the gut microbiota. Excitedly, new research has began to demonstrate how changes within the gut can affect changes in learning and memory in animal models.6,7 It may be that complex interactions between NPS and gut microbiota impact mechanisms that result in cognitive benefit.
It is important that NSP’s in cereal seeds, grains, legumes, plants and fungi are included as part of a healthy diet, as they make a significant contribution to human health and nutrition. Understanding the benefits for cognitive function and the mechanisms underlying the nutritional significance of dietary NSP for brain health is an exciting area for researchers, industry and consumers to explore.
References:
- Kumar, V., et al., Dietary roles of non-starch polysaccharides in human nutrition: a review. Critical reviews in food science and nutrition, 2012. 52(10): p. 899-935.
- Talbott, S. and J. Talbott, Effect of beta 1,3/1,6 glucan on respiratory tract infection symptoms and mood state in marathon atheletes. Journal of Sports Science and Medicine, 2009. 8: p. 509-515.
- Best, T., E. Kemps, and J. Bryan, Saccharide effects on cognition and well-being in middle-aged adults: A randomised controlled trial. Developmental Neuropsychology, 2010. 35: p. 66-80.
- Hirano, E., et al., P B-2, a polysaccharide fraction from lichen Flavoparmelia baltimorensis, peripherally promotes the induction of long-term potentiation in the rat dentate gyrus in vivo. Brain Research, 2003. 963: p. 307-311.
- Edagawa, Y., et al., Systemic administration of lentinan, a branched β-glucan, enhances long-term potentiation in the rat dentate gyrus in vivo. Neuroscience Letters, 2001. 314(3): p. 139–142.
- Lyte, M., Microbial endocrinology and nutrition: A perspective on new mechanisms by which diet can influence gut-to-brain communication. PharmaNutrition, 2013. 1(1): p. 35–39.
- Heijtz, R.D., et al., Normal gut microbiota modulates brain development and behavior. Proceedings of the National Academy of Sciences of the USA 2011. 108(7): p. 3047-3052.
