by Ms Yang Dimeng and Dr Liu Mei Hui
Type 2 diabetes (T2D) affects 415 million people in the world today. This number is expected to rise to 642 million by 2040. In Singapore, the Ministry of Health has declared a “War on Diabetes”. Major efforts will be made over the next 2-3 years to develop and deploy programs to prevent diabetes, and improve the care of patients with diabetes with a focus on optimizing care in a sustainable manner.
Optimal blood glucose control has been shown to reduce diabetes-related complications such as kidney diseases and retinopathy. One of the cornerstones of diabetes management involves dietary modifications to reduce postprandial hyperglycaemia. In addition, the drug acarbose which delays glucose absorption and reduces postprandial blood glucose response has been shown to reduce the incidence of type 2 diabetes. Several epidemiological studies indicate that the consumption of plant-based diets which are low in glycaemic index (GI) and glycaemic load (GL) is associated with lower risk of T2D. In randomized controlled trials, diets with a reduced GL such as the Mediterranean diet and low GI diets, have improved risk factors control for T2D.
GI measures how a carbohydrate-containing food raises blood glucose as compared to a reference food. Hence, foods with high GI raise blood glucose more than foods with low GI. This understanding of the GI would allow one to choose the appropriate foods to achieve optimal blood glucose control and reduce diabetes-related complications. As such, major diabetes organizations around the world such as the American Diabetes Association, Canadian Diabetes Association and Diabetes UK, advise people with diabetes to use GI as part of their diet management.
Despite guidelines and recommendations, it remains a challenge for the consumer to adopt a low GI diet. The GI values of food can vary in the same food category and under different preparation/processing methods. Adding to the complexity of the issue, Asian diets fundamentally consist of a large proportion of white rice, noodles and other refined flour based products, which limits their ability to choose and pick the correct food choices.
Fiber and the glycemic index
The fiber content of a meal plays an important role in controlling blood glucose levels and insulin response post-meal because of its effect on gastric emptying and glucose absorption from the gut. Soluble fibers slow digestion and the release of glucose into blood while insoluble fibers help bowel movement and prevent constipation. In general, food high in fiber are likely to be low in GI.
As consumers actively seek foods that offer improved nutrition and taste, food companies have started to enrich their products with fiber of different health properties. These functional fibers and their applications have gain acceptance in the functional food sector. For example, soluble fiber can be found in fortified beverages, breads and cereals. While the short-term beneficial effect of fiber-rich whole foods on glycemic profile is documented, there have not been enough trials to demonstrate that soluble fiber as a supplement form would be an effective tool for improving glycemic control in the long term. Also, while results from correlation studies indicate that fiber in the diet are protective against diabetes, long-term clinical trials on whole foods rich in soluble fibers to corroborate these observations remains lacking.
Choosing the right grain
At the Public Health level, policy makers have focused their attention on increasing whole grain intake as a general strategy to lower one’s glycemic response to food. In Singapore, dietary guidelines set by the Health Promotion Board recommend adult Singaporeans to consume whole grains instead of refined grains wherever possible. Whole grains are rich in fiber, vitamins, minerals and various phytochemicals. They are also relatively high in antioxidants. In contrast, most of these nutrients are removed in the grain-refining process to produce refined grains. Epidemiological studies suggest that regular consumption of whole grain helps to regulate blood glucose levels by slowing down digestion and may control insulin metabolism. While more research is needed on the mechanism for protection, increased consumption of whole grains has been consistently correlated to a decrease risk of type 2 diabetes.
Yet, consumers must be cautioned that many foods legally marketed as whole grains may not actually be beneficial to health. The current definition of whole grain also does not account for its fiber content and many whole grain products on the shelves may not be fiber-rich. Processing techniques such as grinding, puffing and flaking may also degrade natural antioxidants and reduce the fiber content. Whole grains food products may also contain additives and high sugar content to compensate loss in sensory properties.
Future Food innovation in Health
The addition of whole grains in food products is one of many strategies to lower glycemic response. Novel solutions to alter GI of foods beyond the most popular methods are pertinent to provide consumers with more choices and variety. This will require innovative ways to alter commonly available food products to reduce postprandial glycemia and maintain sensory characteristics. The Future Food for Health project is part of a multi-disciplinary effort to leverage on the collaborative and interdisciplinary network of clinical, basic and public health expertise in the National University of Singapore (NUS) on the War on Diabetes in Singapore. The effort is designed to enable and inform population interventions that will have an impact on health in a sustainable manner by introducing innovative foods that are ‘health promoting’ based on rigorous human experiments.
As part of this effort, the Food Science and Technology (FST) programme at the NUS has developed several functional staple foods such as the anthocyanin fortified bread, or purple bread. Bread is a popular food for many people across the world. However, it is rich in carbohydrates and contains a high amount of rapidly digestible starch. This makes the production of low GI bread products particularly challenging. Current approaches for developing healthier bread are dominated by adding whole grains and fibers, aiming to slow down starch digestion. However, this method may change the texture of the bread significantly and reduce palatability. There is recent rising demand on the use of natural and plant-based products such as plant extracts rich in phytochemicals and flavonoids as food ingredients. Experimental studies have shown that anthocyanins, a class of flavonoids, can help prevent cardiovascular and neurological diseases and cancer. They also play a role in controlling obesity and diabetes by inhibiting digestive enzymes and reducing blood glucose levels. In in-vitro digestion models, the carbohydrate digestion rate of anthocyanin-fortified bread was slowed by 20% while antioxidant properties of the anthocyanins remained largely heat stable. Hence, anthocyanin-fortified bread can provide consumers with a healthy alternative to regular bread without compromising on the sensorial properties accustomed with white bread.
The NUS FST programme has also identified proanthocyanidins from the common local vegetables lady’s finger(okra) that function in a similar mechanism as the anti-diabetic drug, acarbose. Recent work involves the incorporation of these proanthocyanidins into noodles for the creation of low GI noodles. These products will mimic low GI alternatives to staple carbohydrates which may help in diabetes prevention and management and eliminate the need for consumer to make conscious behavioral changes since sensory and textural characteristics of staple is preserved.
Apart from developing new food products incorporated with novel functional ingredients, GI can also be influenced by food processing techniques. With advancements in microfluidics, structured, multi-component micro-particles made from food derived materials can be precisely made and controlled. Manipulating the “microstructure” of the food can affect the way it is digested, its texture, palatability and other characteristics such as flavor when incorporated into foods. It is also possible to introduce encapsulated actives components, which will provide opportunities for further optimization and incorporation of novel ingredients in food structures to maximize functionality. As a part of the Future Foods for Health project, NUS FST and the NUS Faculty of Engineering are also exploring the possibility of creating carbohydrate based foods from precisely controlled raw materials with reduced GI and matching or improved sensory qualities.
Hence, while initiatives to choose more whole grains is a prudent one, helping consumer make choices to choose the correct type of grain is essential too.
Consumer health behavior is complex and multidimensional. Smart consumer choices need to be made constantly to achieve the desired outcome. Yet, this is made increasingly challenging with the myriad of food choices we are presented with. On the other hand, it would be interesting to approach the problem from a different perspective. With food innovation and processing technology, an effective way to change eating behavior can be achieved by changing food choices without intensive dietary counseling or modification of behavior. The development of novel food technology will harness the capabilities in a comprehensive level to improve health in the population level and provide an additional strategy to aid in our battle against diabetes.
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About the Authors
- https://www.moh.gov.sg/content/moh_web/home/pressRoom/highlights/2016/Budget2016/ the-fight-against-diabetes.html
Mei Hui, Liu (Ph.D) is a lecturer from the Food Science and Technology Program of Department of Chemistry, National University of Singapore (NUS). Dr. Liu was a recipient of the A*STAR graduate scholarship (NUS) and A*STAR postdoctoral fellowship (Cornell University). Her research interests include understanding the molecular progression and dietary management of diabetes in the Singapore population. She is also one of the investigators in the Future Food for Health (FFH) project and coordinates the multi-disciplinary project.
Ms Yang Dimeng completed her Bachelor of Applied Science (Honors) degree in National University of Singapore, specializing in Food Science & Technology. She has experience working with nutritional products at companies such as Abbott Nutrition and DSM Nutritional Products. For her final year project, Dimeng worked closely with Abbott Nutrition to develop and characterize the functionality of adult nutrition powder. She also has keen interest in functional food, nutrition and public health issues. Currently, she is working as a research staff for the Future Food project.