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What Are The Negative Health Effects Of Sugar?

Last updated Sept. 13, 2016

Approved by: Maulik P. Purohit MD, MPH

Added sugars, like sucrose and high fructose corn syrup, are high in calories and contain no vital nutrients.

You may not be conscious of the fact that the foods you consume everyday may have added sugars contained amongst its list of ingredients. These sugars, when consumed in excess, have exhibited a causal link to type II diabetes, metabolic syndrome, cancer, cardiovascular disease, and obesity, to name a few disorders. It is thus important to have an awareness of sugar intake and the damaging effects it can have on one’s body.

These added sugars, like sucrose and high fructose corn syrup, are high in calories and contain no vital nutrients. Calories from added sugar sources are coined as “empty calories”. When 10-20% of your caloric intake each day is sugar, this can contribute to eventual nutrient deficiencies.

Sugar is proven to be detrimental to one’s teeth, as it provides energy that can be easily digested by harmful bacteria in the mouth. A study published by the American Society for Clinical Nutrition in 2003 concluded that sugar and carbohydrates stimulate bacteria to generate acid and lower the pH, allowing for teeth to demineralize and cause a breakdown of the tooth enamel. This research emphasizes the need to integrate oral hygiene instruction into one’s everyday diet.

Prior to sugar entering the bloodstream, it is broken down in the digestive tract to similar compounds, glucose and fructose. Glucose is a form of sugar that exists in every living cell. If our bodies do not intake enough glucose, our bodies will produce it on their own. The body, however, cannot produce fructose. There is no biological requirement for it, therefore rendering it unnecessary to intake fructose through food and drink.

If consumed in small amounts or post workout, fructose is not worrisome and will be converted into glycogen that is stored in the liver, until a further need arises. Once the liver becomes full of glycogen, it will get overloaded with fructose, therefore having to convert excess fructose to fat. During this process, the fat is transported out of the liver as VLDL cholesterol particles, or very low-density lipoproteins. Yet, not all of this fat may be properly transported out of the liver. This has the potential to lead to non-alcoholic fatty liver disease (NAFLD), a clinical condition associated with metabolic syndrome.

It is important to note that there is vast individual variability concerning this process. Healthy, active individuals are able to tolerate higher levels of sugar than those who are less active and have a higher caloric and carbohydrate intake.

Sugar can have an unfavorable effect on insulin resistance. Insulin, a vital hormone in the body, permits glucose from the bloodstream to enter cells, allowing for glucose breakdown instead of fat metabolism. Excessive glucose content in the blood is very toxic. With poor diet and excessive sugar intake, insulin stops performing its normal function, in turn giving rise to insulin resistance. Emerging evidence from recent studies, such as one published in the Global Journal of Medicine and Public Health, proposes that excessive fructose intake is an instrumental factor in the advancement of metabolic syndrome. Several studies have concluded that insulin resistance is able to give rise to many other diseases including obesity, cardiovascular disease, and type II diabetes. When cells develop an insulin resistance, the pancreas produces more insulin, chronically elevating blood sugar to dangerous levels. This condition is then classified as type II diabetes.

Several researches show that individuals who consume higher amounts of sugar are at a much higher risk for cancer. One study conducted at the University of Manchester Medical School in 1983 showed a possible link between high-sugar diets and an incidence of breast cancer, as insulin is a requirement for the proliferation of normal breast tissue. 

Similar to commonly abused drugs, sugar triggers dopamine release in the reward center of the brain. This indicates that for those individuals who are more susceptible to addictive behaviors, an addiction to sugar and other junk foods is possible. A study released in 2004 by the American Society for Clinical Nutrition exposed a correlation between the consumption of beverages containing high-fructose corn syrup and obesity. They found that dietary fructose, found in calorically sweetened beverages, might be related to the obesity epidemic, as it contributes to weight gain and increased energy intake. 

There is evidence that sugar may be one of the primary causes of heart disease due to the damaging effects of fructose on metabolism. Fructose can increase blood levels of triglycerides and LDL cholesterol, a risk factor for developing heart disease. It is important to be attentive to your sugar intake and your risk factors for conditions that can be increased from sugar intake. Proper education on dietary recommendations and consequences of unhealthy eating habits is vital to staying healthy. 


Touger-Decker R, Van Loveren C. Sugars and dental caries. The American Journal of Clinical Nutrition. 2003; 78(4):8815-8925. 

Gunnars, K. 10 Disturbing Reasons Why Sugar is Bad For You [Internet]. [cited 2014 Oct 27]. Available from: http://authoritynutrition.com/10-disturbing-reasons-why-sugar-is-bad/

Basciano H, Federico L, Adeli K. Fructose, insulin resistance, and metabolic dyslipidemia. Nutrition and Metabolism. 2005; 2(5): 1-14. 

Seely S, Horrobin D. Diet and breast cancer: The possible connection with sugar consumption. Medical Hypotheses. 1983; 11(3): 319-327. 

Bray G, Nielsen S, Popkin B. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. The American Journal of Clinical Nutrition. 2004; 79(4): 537-543. 

Helpful Peer-Reviewed Medical Articles:

Burt, B. A., & Pai, S. (2001). Sugar consumption and caries risk: a systematic review. Journal of dental education, 65(10), 1017-1023.

Rada, P., Avena, N. M., & Hoebel, B. G. (2005). Daily bingeing on sugar repeatedly releases dopamine in the accumbens shell. Neuroscience, 134(3), 737-744.

Lustig, R. H., Schmidt, L. A., & Brindis, C. D. (2012). Public health: the toxic truth about sugar. Nature, 482(7383), 27-29.

Bray, G. A., & Popkin, B. M. (2014). Dietary sugar and body weight: have we reached a crisis in the epidemic of obesity and diabetes? Health be damned! Pour on the sugar. Diabetes Care, 37(4), 950-956.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 13, 2016
Last updated: Sept. 13, 2016