Oranges And Blood Sugar Control

Introduction

Blood sugar control

Blood sugar, also known as ‘blood glucose’, constitutes the primary source of energy in our body. It comes from the carbohydrates (glycaemic) present in food, mainly in the form of starches and sugar.¹ Interestingly, the majority of the carbohydrates taken in our diet are not available in the form of glucose, which is a monosaccharide (the simplest form of sugar that can be absorbed by the body). Carbohydrates are composed of complex di- and polysaccharides that are required to be broken down to glucose and absorbed by the intestine into the bloodstream.² 

Soon after a meal, carbohydrates are broken down into glucose through digestion, and it is absorbed into the blood. This increases the blood glucose levels; the glucose is then transported through the circulatory system to other cells in the body or the liver where it is stored as glycogen (polysaccharide form). This regulation of blood sugar level is largely carried out by a good balance of endocrine hormones produced by the pancreas. The main hormones in the pancreas that affect blood sugar are insulin, glucagon, somatostatin, and amylin. While insulin helps in lowering the blood sugar level, glucagon elevates the blood sugar level and somatostatin balances both insulin and glucagon. As such, the human body tries to maintain homeostasis in blood glucose level, and in a healthy individual, it ranges between 72 to 108 mg/dL.^3,4

It's important to fuel our body cells to stay healthy. We must also make sure our blood sugar levels stay just right - not too low (hypoglycemia) or too high (hyperglycemia). If the levels are too high for a long time, it can make us sick and cause problems like diabetes, heart issues, blindness, and possibly a coma.^3,4 So, it's vital to control and handle blood sugar levels. A good way to do this is to eat a healthy diet with lots of fruits and vegetables.

Among the plant-based foods consumed, citrus fruits are a promising source in the management of blood sugar levels. One such citrus fruit that we will discuss in this article is ‘Oranges’. 

Oranges and blood sugar control

Oranges, scientifically known as ‘Citrus sinensis L.’, are the most cultivated and produced citrus globally, constituting 50-62% of the total citrus production.⁵ Moreover, approximately 33% of the global orange production is processed into juice, contributing to being the most frequently consumed fruit juice worldwide.⁶ 

Importantly, oranges are well enriched with a variety of phytonutrients which are vital for both health benefits and disease prevention. Here, ‘phytonutrients’ indicate that plant nutrients have particular biological effects in promoting human health. Some of the commonly found bioactive compounds in oranges include ascorbic acid (vitamin C), folic acid, pantothenic acid, and improved health, including blood sugar control. 

Nutritional composition of oranges 

To maintain good health, a person's diet must include critical micronutrients in addition to carbohydrates, proteins, and fats. Oranges are a great source of these necessary microelements, some of which are vitamin C, flavonoids, and dietary fibres.

Vitamin C

Oranges are well known for their extraordinary content of vitamin C. Literature reports demonstrate that on average the vitamin C content of oranges ranges between 29.0 and 82.5 mg/100 mL, and among all the orange varieties navel and pineapple oranges contain the highest vitamin C contents of 82.5 and 78.0 mg/100 mL of juice, respectively. Vitamin C is a powerful micronutrient that acts as an antioxidant and aids in numerous body functions such as the development and maintenance of connective tissues, shields the body from radical damage, protects the immune system, reduces allergic reactions, and functions as a therapeutic agent for many diseases and disorders.^7,8

Flavonoids

Citrus fruits contain flavonoids which are aromatic secondary plant metabolites. In oranges, the most abundantly found flavonoids are hesperidin and narirutin. Flavonoids are good for you. They help with antioxidants and can fight germs in your body. They also can help your body not be so swollen. They are important to have in your diet. Data reports show freshly squeezed orange juice contains 28.6 mg/100 mL of hesperidin, followed by 5.2 mg/100 mL of narirutin and 1.89 mg/100 mL of didymin.^9,10,11

Dietary fibres

Dietary Fibres constitute the edible part of plant-based meals that are not easily broken down and absorbed by the body's enzymes. Oranges are a good source of dietary fibres (2.4g per 100 grams) which includes both soluble and insoluble fibres like pectin (15.7–16.3% DM), cellulose and hemicellulose (16.6–18.1% DM), and lignin (2.2–3.0% DM) (12). According to major food and health organisations such as the UK Scientific Advisory Committee on Nutrition, the United States National Academy of Sciences, and the Institute of Medicine, an adult's recommended total dietary fibre intake should be at least 25g per day.¹³ 

Additionally, orange fruit contains high concentrations of minerals including calcium and potassium. While potassium regulates blood pressure and heart rate, calcium helps in stimulating the digestive juices, thus, comforting constipation. 

How do the nutritional components of oranges influence blood sugar levels?

High concentration of glucose level in the blood is often associated with health diseases including diabetes. Diabetes Mellitus (DM) is a group of diseases that is caused due to inadequate control of blood glucose levels in the body. DM is characterised by hyperglycemia (increase in blood glucose level) which induces oxidative stress (a state of imbalance between free radicals in cells/tissue) and inflammation. Additionally, DM is also associated with insulin resistance.¹⁴ 

The nutritional components of oranges help in blood glucose control in the following ways: 

Vitamin C

Many studies have shown that vitamin C is associated with a reduced risk of developing diabetes mellitus (DM). Norfolk Prospective Study on the association between plasma levels of vitamin C and risk of DM demonstrated an inverse relationship between the vitamin C plasma levels and diabetes risk.¹⁵ This association is further supported by studies conducted by other researchers like ‘Dietary antioxidant intake and risk of type 2 diabetes’ by Montenen J et al. in 2004¹⁶ and ‘Antioxidant status in patients with uncomplicated insulin-dependent and non-insulin-dependent diabetes mellitus’ by Maxwell SR in 1997.¹⁷ Vitamin C acts as an antioxidant that reduces glucose toxicity in the body. They also play a role in preventing the decrease of pancreatic β-cells and thereby insulin production. Moreover, literature also suggests that vitamin C plays a protective role against free-radical production due to long-term hyperglycemia.^8,18

Flavonoids

Flavonoids possess several positive health effects on a variety of metabolic disorders including cardiovascular diseases, obesity, cancer, and diabetes. In terms of diabetes management, research and clinical studies have shown that flavonoids aid in the regulation of carbohydrate regulation, insulin secretion and signalling, glucose uptake by cells as well as in adipose deposition.

They function by targeting multiple molecules involved in the glucose regulation pathway in the body like enhancing the proliferation of β-cells in the pancreas, stimulating the release of insulin, and improving hyperglycemia through the regulation of the liver's glucose metabolism. Specifically, hesperidin, which is a commonly found flavonoid in oranges, can effectively lower blood glucose levels by affecting glucose enzymatic activities.^11,19

Dietary Fibres

Consumption of fibre-supplemented oranges results in lowering of postprandial (after meal) glycaemic response of both glucose and insulin levels in the body. Additionally, viscous fibres of oranges can prolong the absorption rate of nutrients such as monosaccharides (for e.g., glucose) which results in a release of satiety (fullness) regulating hormones in the body (like glucagon-like peptide 1 (GLP1)). GLP1, in turn, prompts insulin secretion post-meal to ensure the maintenance of glucose homeostasis in the body.^20,21 

Glycaemic index of oranges

What is the Glycaemic Index (GI)?

The glycaemic response (GR), which is the appearance of glucose in the bloodstream after eating, is a normal physiological event that is influenced by the rate at which glucose enters the circulation, the quantity of glucose absorbed, the rate at which glucose leaves the circulation as a result of tissue uptake, and the hepatic regulation of glucose release. As such, the lycaemic Index (GI) is a methodological tool which was created to provide information on the GR of a food item. In fact, GI is a ranking system that calculates the effect carbohydrate has on the blood glucose level. It is therefore a characteristic of the meal itself, an index or percentage that is based on how quickly glucose present in a food is digested and absorbed in the body. So, high GI foods (GI > 70 on the glucose scale) are foods with carbohydrates that are rapidly digested, absorbed, and metabolised, whereas low GI meals (GI < 55 on the glucose scale) are those with carbohydrates that are slowly digested, absorbed, and metabolised.^22,26 

Additionally, Glycaemic Load (GL) is another concept that measures the impact of a food item on blood glucose level. It considers the speed of glucose conversion of a food item which is the GI and the amount of carbohydrate present in that food item.^22,27

Oranges, which are an excellent source of nutrition with valuable health benefits, have a GI of 35 and GL of 4.1, which categorises it to be a low GI and low GL food, respectively²⁵. 

Benefits of Glycaemic Index

Foods having a lower GI like oranges tend to break down slower than foods having a higher GI like white bread. As a result of this low GI foods are less likely to trigger a sudden spike in blood sugar levels in the body. As such, oranges help in maintaining stable blood sugar levels. 

Secondly, recent studies have demonstrated that low GI food items like oranges can effectively reduce glycated haemoglobin (HbA1c) and fasting glucose, and thereby may aid in blood sugar control in pre-diabetic or diabetic patients.^23,24,26 

FAQ’s

What is blood glucose level? 

Blood sugar level or blood glucose level is a measurement that indicates the amount of glucose present in the blood. Carbohydrates in food are broken down into glucose through the process of digestion. This glucose which is then absorbed into the bloodstream is transported into other cells of the body or into the liver for storage. As such, blood glucose levels are regulated up and down throughout the day. 

Why is it important to maintain the level?

It is important to maintain a homeostasis of the blood glucose level in the body because spiking of blood glucose levels too high (hyperglycaemia) or dropping too low (hypoglycaemia) is extremely dangerous to the body. This can lead to chronic health disorders and diseases such as diabetes, coronary disorders, blindness, etc. For a healthy adult, the blood glucose level should be maintained between 72 to 108 mg/dL.

How can oranges help to maintain blood glucose levels?

Oranges, with their refreshing flavour and vibrant colour, are not only a delightful addition to your diet but also offer a myriad of health benefits. Oranges are enriched with multiple phytonutrients that can have a positive impact on your overall well-being. Among their many virtues, oranges are known to assist in blood sugar control, making them an essential choice for those seeking to manage their glucose levels effectively.

Summary

To summarise the phytonutrients in oranges that help in blood sugar control are: 

Vitamin C is a water-soluble antioxidant that can lower blood glucose levels by producing a foraging effect on the free radicals, which are generated by long-term hyperglycaemic conditions. As a result, there is an improvement in insulin resistance and β-cell function of the pancreas.

Secondly, dietary flavonoids present in oranges can mitigate diabetic complications by protecting the β-cells of the pancreas and stimulating insulin production in the body. They also help in inhibiting glycogenolysis (the process of breakdown of glycogen into glucose) and gluconeogenesis (the biochemical process in which glucose is formed from a non-hexose substrate such as lactate) and delaying the gastric emptying of carbohydrates in the body.

Thirdly, orange pomace (a fibre-enriched by-product of orange) also helps manage blood glucose by potentially controlling glucose spikes in the body after a meal.