Sugar is a sweet-tasting carbohydrate and is a common ingredient in our diet. Biochemically, ‘Simple sugars’ or Monosaccharides include glucose, fructose and galactose. “Table sugar” refers to sucrose, which is a disaccharide consisting of glucose and fructose. It is commonly derived from sugarcane. Sugar is commonly used as a sweetener for various processed foods like cakes, cookies, sweets, beverages (tea, coffee, carbonated drinks), etc.
Sugars play a significant role in biochemical functions of the body. While fructose is found in fruits and galactose is found in milk; glucose is the major simplest circulating sugar in our body. Most of the ingested carbohydrates are converted into glucose and this is transported throughout the bloodstream to be utilised by the cells of the body. Disaccharides, which contain two monosaccharide molecules, include lactose, maltose and sucrose. Lactose is found in milk and maltose in certain grains. Sucrose has a vast application in cooking as a table sugar. When consumed, it gets broken down into fructose and glucose, which are then utilised by the body. Starch, a polysaccharide, is a polymer of glucose. It is found in cereals (rice, wheat) and vegetables (potato).
Based on the sources, the sugars can be found in 3 forms:
- Natural: fruits, vegetables, honey, milk products.
- Added: biscuits, cereals, beverages, desserts, processed foods.
- Products of digestion of more complex carbohydrates: bread.
Carbohydrates are an essential part of nutrition. It is a macronutrient which provides calories to the body for various metabolic processes. According to the Dietary Guidelines for Americans, carbohydrates should make up 45 to 65 percent of the total daily calories. However, there is a restriction for intake of ‘Added sugars’. The World Health Organization (WHO) recommends reducing the intake of free sugars to less than 10% of the total energy intake. It also encourages a further reduction to below 5%. Free sugars include monosaccharides and disaccharides.
Sugar is a concentrated source of calories. That means lesser amount contains more calories. Excessive sugar consumption has been implicated in the development of various health problems like diabetes, obesity, cardiovascular disease, tooth decay, cancers, liver disease, dementia, etc. The detrimental effects of sugars on human health have been elaborated below. Furthermore, the Food and Drug Administration has specified to limit the intake of ‘Added sugars’ below 50 grams per day. The American Heart Association (AHA) recommended the maximum amount of added sugars of 150 calories/day (37.5 grams or 9 teaspoons) for men; and 100 calories/day (25 grams or 6 teaspoons) for women.
Sugar has the following detrimental effects on human health:
Weight gain and Obesity: WHO has shown that a high sugary food intake adds to the overall energy intake of the body. This extra energy gets stored in the body in the form of visceral fat accumulation, which leads to increased weight gain and obesity.
Diabetes and Metabolic syndrome: High blood sugar stimulates the release of a hormone called Insulin, which lowers the blood glucose. Insulin is a major controller of blood glucose. When a person consumes high sugar diet, there is a weight gain and obesity. These predispose the body for insulin resistance. Studies have shown that obesity and insulin resistance are major risk factors for Type 2 Diabetes Mellitus. Weight gain and obesity are also associated with metabolic syndrome owing to elevated lipid levels in the blood.
Increased risk for cardiovascular diseases: Heart disease is the number one cause of death worldwide. Clinical evidence shows that high sugar diet intake causes obesity, inflammation, high triglyceride (lipid) levels, high blood glucose levels, and high blood pressure – all these are risk factors for heart disease. Consumption of high amount of added sugars have also been implicated in development of atherosclerosis, in which the arteries are clogged with fatty deposits.
Increased risk for cancer: High sugar intake is associated with Insulin resistance, diabetes, obesity, and inflammation. These are risk factors for development of certain cancers, especially of gastrointestinal system.
Tooth decay and dental problems: WHO has reported that sugars are the most important dietary factor responsible for development of dental caries. The bacteria feed on sugars releasing acid byproducts which demineralize the teeth. Bacterial growth further spreads the infection from the gums, and cause endocarditis (heart disease) through bloodstream dissemination.
Skin problems like Acne: High sugar foods quickly increase the blood glucose and insulin levels, which thereby increases androgen secretion. This stimulates the skin glands for more oil production and inflammation leading to formation of acne. Moreover, high sugar diet has shown to enhance the formation of Advanced Glycosylated End products (AGEs), which play a key role in skin aging. This results in premature skin aging and formation of wrinkles. Cellular aging is also increased due to reduction in telomerases.
Impairment of immune functions: Immunity is the defence mechanism of the body to fight against various infections. The bacteria and fungi feed on the glucose; hence high blood glucose favours the growth of these organisms leading to increased infection risk.
Impairment in cognition and mood: High sugar consumption impairs higher mental functions like cognition and mood. It results in poor memory and cognitive decline, leading to diseases like dementia and Alzheimer’s. Children consuming high amounts of sugar-containing energy drinks have been associated with development of hyperactivity, lack of concentration, insomnia, anxiety, and poor performance. They also tend to have increased tendency for alcohol and smoking abuse. Moreover, after consuming high amount of sugars, there is a sudden rise in blood glucose followed by a sudden crash. This stimulates stress hormones which attempts to increase blood glucose levels. This stress response brings out anxiety, restlessness, tremors and irritability.
Displacement of important nutrients: When people consume high sugar diet, it makes up for most of the caloric intake. Therefore, the intake of other essential nutrients like vitamins & minerals is compromised leading to their deficiency.
Fatty Liver disease: Liver utilizes glucose and fructose and converts them into storage form, glycogen. When the glycogen amount is saturated, it is in turn converted into fat and stored in the liver. Hence, excess sugars can lead to fat deposition in the liver causing liver disease termed as NAFLD i.e. Non-Alcoholic Fatty Liver Disease.
Other health risks: High sugar diet has been shown to cause kidney disease and gout.
Conclusion: Consumption of high amount of sugars, especially added sugars, have bad effects on health including: weight gain, obesity, diabetes mellitus, metabolic syndrome, increased risk for cardiovascular diseases & cancer, dental problems, skin problems, early cellular aging, impairment of immunity, impairment of cognition, nutrient displacement, fatty liver disease and so on. Hence it is advisable to have sugar consumption within recommended limits. Added sugars in various forms like soft drinks, beverages, baked foods, canned and processed foods, etc. needs to be restricted. For instance, sugar addiction should be avoided whenever possible.