Nutrition

 

Dietary and Exercise Tips for Managing Diabetes

By Michael Sakarya [Get Well Clinic]

Introducing diabetes

Diabetes mellitus is a term encompassing various disorders characterized by hyperglycemia, meaning increased blood glucose levels. It arises due to a combination of insulin resistance and dysfunction of the cells in the pancreas that secrete insulin1. In type 1 diabetes, the cells in the pancreas that secrete the hormone signal insulin are attacked by the body’s own immune system, causing a complete lack of insulin secretion. In type 2 diabetes, genetic and lifestyle factors can cause insulin resistance where the body’s cells do not respond to insulin as normal. As a result, there is reduced uptake of blood glucose by the body’s cells and increased glucose production by the liver. The pancreas compensates by excessively producing insulin, but in the long term, the pancreas begins to fail, and insulin secretion decreases. Hyperglycemia manifests in both type 1 and type 2 diabetes.

“Diabetes” is derived from the Greek word meaning “to pass through”, while “mellitus” refers to the Greek word meaning “like honey”. The medical term “diabetes mellitus” thus refers to a common symptom of diabetes called glycosuria, meaning the presence of glucose in the urine. The body must carefully regulate blood glucose levels at approximately 0.9 grams of glucose per litre of blood (5 mmol/L)2. Thus, the kidneys will discharge glucose when there is an elevation in blood glucose. Diabetes often presents in individuals with pre-existing conditions like obesity or hypertension and is a major risk factor for various other metabolic diseases including cardiovascular and liver diseases3,4. Thus, it is imperative to take measures to control and reduce the severity of diabetic symptoms in order to prevent complications and promote a good quality of life. Although it is necessary to adhere to medication regimens prescribed by one’s family doctor, dietary and exercise strategies that accentuate the effect of medications exist. This article will outline scientific evidence supporting the benefits of various strategies that can be incorporated into daily living to help manage blood glucose levels and promote a positive long-term outcome.

Whole grains vs. processed grains and the benefit of fibre

It is beneficial for individuals with diabetes to consume whole grains rather than processed grains. Whole wheat grains are composed of 3 major structures: the bran, the germ, and the endosperm (see Figure 1). Each contains unique nutrients including fiber, antioxidants, minerals, vitamins E and B, carbohydrates (typically long glucose chains), and protein. Whole grains are composed of all 3 structures while processed (or refined) grains lack the nutrient-rich bran and germ, leaving behind only the glucose-rich endosperm5.

Figure 1. Whole grains are composed of 3 structures with unique nutrients: the bran, the germ and the endosperm21.

Firstly, a study of 31 adults with type 2 diabetes found a reduction in 24-hour blood glucose levels when consuming whole grains compared to processed grains6.  Interestingly, there is also some evidence associating whole grain or fiber intake with prevention of type 2 diabetes7. It was proposed that the anti-inflammatory nutrients and minerals found in whole grains and other fiber-rich foods are responsible for these benefits. In addition, fiber is a type of carbohydrate that is incapable of being digested by cells in the small intestine. Thus, fibers are shuttled into the large intestine where an assortment of bacteria, collectively called the gut microbiota, await their fiber-rich feast. Unlike intestinal cells, the gut microbiota is equipped with appropriate enzymes to digest fiber. A healthy gut microbiota benefits human health in countless ways8. To date, research suggests that fiber intake elevates insulin sensitivity and reduces HbA1c (hemoglobin with glucose attached to it) via improvements in gut microbiota health9. As whole grains are rich in fiber, one study also found a reduction in HbA1c upon whole grain consumption10. It is worth noting that whole grains are rich in insoluble fiber rather than soluble fiber. Thus, the insoluble fiber in whole grains is largely responsible for improved gut microbiota related health benefits9. That said, soluble fiber intake can also improve symptoms in patients with diabetes. A review of several studies investigating the effects of soluble fiber on type 2 diabetes reported some evidence of reduced HbA1c and fasting blood glucose levels. Soluble fibers, like β-glucan and psyllium, delay gastric emptying, meaning the rate of stomach content emptying into the small intestine10. Soluble fibers also form a viscous solution in the small intestine which lowers the absorptive rates of carbohydrates. Consequently, blood glucose levels of diabetic patients do not drastically elevate following a meal12,13.

Thus, consuming whole grain foods is recommended to manage blood glucose levels. The insoluble fiber, anti-inflammatory nutrients and minerals found in whole grains are largely responsible for lowering blood glucose. In addition, foods high in soluble fibers are excellent options for regulating blood glucose levels, especially following a meal, as they enhance the regulation of glucose absorption from the small intestine into the blood.

Good sources of fiber and whole grains

As previously alluded to, fiber is an umbrella term encompassing both soluble and insoluble fibers which are found is a variety of foods. Soluble fiber is directly associated with blood glucose regulations by lowering both gastric emptying and glucose absorption from the small intestine into the blood. On its own, insoluble fiber benefits blood glucose regulation by improving the gut microbiota. Thus, it is important to know which foods contain each type of fiber.

To begin, excellent sources of soluble fiber include barley, oats, reishi, maitake and shiitake mushrooms, prunes, avocados, and oranges14,15. Great sources of insoluble fiber include raw vegetables, such as broccoli, cabbage, carrots, cauliflower, and spinach, avocado, guava, pears, prunes, corns, beans, and… whole grains15! Some great sources of whole grains include rye, quinoa, oats, millet, buckwheat, and brown rice16. Importantly, whole wheat products are not the same as whole grain. Ingredient labels of whole grain products should clearly state “whole grain, including the germ”. All of these foods are excellent choices to consume daily for those aiming to increases regulation of blood glucose levels. Of course, most foods contain combinations of nutrients i.e., prunes contain lots of soluble and insoluble fiber. That said, it is important to consume a variety of the food choices listed above to promote a balance diet.

Exercise: lowering blood glucose levels

In general, it is well accepted in the scientific literature that exercise helps maintain good metabolic health in individuals with diabetes. This section will briefly analyse the comparative benefits of aerobic exercise and weightlifting for managing diabetic symptoms.

Aerobic exercise vs. weightlifting

Aerobic exercises are characterized by intense oxygen demands which is met by rapid ventilation. Examples include running, cycling, swimming, jumping rope, kickboxing, and more. Aerobic exercise is sometimes referred to as endurance training. Contrarily, weightlifting is intended to build muscle mass and is considered an anaerobic exercise as it does not typically result in intense oxygen demands. Weightlifting is sometimes referred to as strength training or resistance training.

Multiple reviews involving patient with type 2 diabetes reported that aerobic exercise improves blood glucose regulation17-20. For instance, Yang and colleagues reviewed 12 studies including a total of 595 patients who performed either aerobic exercise or weightlifting for 30-60 minutes, 3 times per week18. They found that aerobic exercise decreased HbA1c by 0.46%. Also, the 10 studies that measured fasting blood glucose showed on average a 0.90 mmol/L decrease, and the 4 studies that measured insulin resistance also reported a decrease18. Another review reported that exercising aerobically for more than 150 minutes per week resulted in a 0.89% HbA1c decrease compared to only a 0.36% decrease when exercising less than 150 minutes per week. Thus, exercising aerobically improved important diabetic symptoms, which were further improved when committing to longer exercise durations per week.

Comparatively, the same review by Yang and colleagues reported that weightlifting lowered HbA1c by 0.32%, fasting plasma glucose by 0.87 mmol/L, as well as insulin resistance. Like the first 2 parameters, the decrease in insulin resistance was slightly less pronounced when compared to aerobic exercise. These results indicate that those with diabetes may experience a marginal advantage from aerobic exercise compared weightlifting. However, the researchers stated that this difference was not clinically important. They explained that both exercise strategies were successful in reducing diabetic parameters and, as it is often easier to follow one type of exercise, it is suggested to commit to either one. Factors like ability to access exercise equipment, residential location, and personal preference will be important factors in deciding which type of exercise is most feasible for a prolonged commitment18.

To summarize, both aerobic exercise and weightlifting can improve blood glucose regulation in diabetic patients. The difference in benefit between both exercise types is ultimately negligible compared to the blood glucose lowering effect of either one exercise. Thus, it is recommended to adopt whichever exercise types can be most readily and sustainably incorporated into daily living for 150 minutes per week.

 

References:

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  2. Güemes, M., Rahman, S. A., & Hussain, K. (2016). What is a normal blood glucose?. Archives of disease in childhood, 101(6), 569-574.
  3. Long, A. N., & Dagogo‐Jack, S. (2011). Comorbidities of diabetes and hypertension: mechanisms and approach to target organ protection. The journal of clinical hypertension, 13(4), 244-251.
  4. Fisman, E. Z., & Tenenbaum, A. (Eds.). (2008). Cardiovascular diabetology: clinical, metabolic and inflammatory facets (Vol. 45). Karger Medical and Scientific Publishers.
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  7. McRae, M. P. (2018). Dietary fiber intake and type 2 diabetes mellitus: an umbrella review of meta-analyses. Journal of Chiropractic Medicine, 17(1), 44-53.
  8. Guarner, F. (2015). The gut microbiome: What do we know?. Clinical liver disease, 5(4), 86.
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  13. Yu, K., Ke, M. Y., Li, W. H., Zhang, S. Q., & Fang, X. C. (2014). The impact of soluble dietary fibre on gastric emptying, postprandial blood glucose and insulin in patients with type 2 diabetes. Asia Pacific journal of clinical nutrition, 23(2), 210.
  14. O’Brien, S. (2020). Top 20 Foods High in Soluble Fiber. Retrieved from: https://www.healthline.com/nutrition/foods-high-in-soluble-fiber#13.-Carrots
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  18. Yang, Z., Scott, C. A., Mao, C., Tang, J., & Farmer, A. J. (2014). Resistance exercise versus aerobic exercise for type 2 diabetes: a systematic review and meta-analysis. Sports medicine, 44(4), 487-499.
  19. Cai, H., Li, G., Zhang, P., Xu, D., & Chen, L. (2017). Effect of exercise on the quality of life in type 2 diabetes mellitus: a systematic review. Quality of Life Research, 26(3), 515-530.
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