Mary Poppins may have recommended adding a spoonful of sugar to make some things a little more palatable, but Americans have taken that benign suggestion and run amok with it.  American consumption of added sugars has increased drastically over the last several decades.  While excessive sugar consumption is arguably the main reason for our epidemic of obesity and type-2 diabetes, the extra empty calories may just be the tip of the iceberg.  As researchers delve deeper into the fundamental causes of the diseases of Western lifestyles, they are starting to see links to sugar consumption; and the evidence implicating added sugars as a contributing factor in the development of heart disease, hypertension, and several common cancers is starting to look pretty good.

What are added sugars? 

Added sugars included table sugar, brown sugar, high-fructose corn syrup (HFCS), honey, molasses, brown rice syrup, agave syrup and other caloric sweeteners in prepared and processed foods — for instance, in soft drinks, iced tea, candy, pastries, cookies and canned fruits.  These added sugars provide no nutritional value.  Some may find it surprising that honey is included here, but honey has 35% more calories per tablespoon than table sugar. 

Extent of the epidemic

Americans now consume over 100 pounds of added sugars per person per year; more than a 50% increase from 30 years ago.  This is equivalent to 22 teaspoons per day!  It is also nearly three times higher than the level found not to “conclusively demonstrate a hazard to the general public.”[1]   So how much of any substance can be consumed before it goes from harmless to toxic?  It is generally accepted that a glass of red wine may have certain health benefits, but we all know the problems that drinking too much can bring.  It is hard not to blame added sugars for the obesity and diabetes epidemics we now face in this country.  In 1980, approximately one in seven Americans was obese and almost 6 million were diabetic.  Thirty years later, coinciding with increased sugar consumption, one in three Americans are obese and more than 14 million are diabetic.

Throughout our history, there has been a suspicious but not incontrovertible association between sugar consumption and disease.  From the late 19th and early 20th centuries there was a very notable increase in sugar consumption as the candy and soft-drink industries grew, along with a parallel increase in diabetes incidence and deaths.  

Is it just the calories?

Conventional recommendations from the Department of Agriculture or the American Heart Association[2] advise reducing sugar intake because of the excess empty calories; that is, the lack of any vitamins, minerals, protein, or fiber, that leads to weight gain and related diseases like diabetes.  High-fructose corn syrup has become one of the most vilified food additives but a growing number of nutrition researchers believe that there is little difference between HFCS and refined sugar, at least with respect to how they are metabolized in your body.  The evidence that HFCS consumption uniquely increases the risk of weight gain is very weak.[3]  HFCS is not used extensively outside the US but obesity rates are increasing worldwide.

Refined sugar (sucrose) is made up of two different sugar molecules, glucose and fructose in a 50-50 mixture.  Other carbohydrates, such as bread, potatoes and pasta break down to glucose.  That is, bread that does not contain HFCS.  Glucose is metabolized and used for energy by all cells in your body.  HFCS is 45% glucose and 55% fructose.  There is also fructose that occurs naturally in fruits, but the absorption rate of the sugar is blunted by the fruit’s fiber content.  Anywhere fructose is found in nature, there is always fiber present.  Fructose is metabolized by the liver and when present in sufficient quantities will be converted into fat.  The speed with which fructose arrives in the liver also influences the rate of conversion to fat.  This is a critical point, since soft drinks are by far the biggest culprits for the glut of sugar consumed, and the fastest way to absorb sugar.   In the 1950’s a typical soda contained 10 ounces; now we have 44 ounce Big-Gulps.  The more sugar consumed, the more insulin your body needs to produce to try and manage it.  In the presence of high insulin levels, more of your calories are stored as fat, creating a vicious cycle that ultimately leads to insulin resistance and fat accumulation in the liver.  And, what has become the most common form of liver disease, non-alcoholic fatty liver (NAFLD), has been linked to an increased consumption of fructose.[4]

Another hormone, leptin, is the satiety hormone.  It sends the signal to your brain to stop eating.  Its effects are essentially disabled in people with insulin resistance.  When leptin isn’t being released, or the signals not processed the way it’s supposed to–as happens in insulin-resistance–your brain doesn’t know you’ve already had enough to eat.  It thinks you’re starving, so you just eat more.  You end up in a vicious cycle of consumption and then disease.  In many obese individuals, leptin resistance contributes to thier difficulty in losing weight.

Sugars, lipids and hypertension

A study published last year looked at the relationship of added sugars to blood lipid levels.  Researchers compared the diets and blood profiles of over 6100 adults from the National Health and Nutrition Examination Survey.  Even after controlling for other variables including body mass index (BMI), physical activity, and total energy expenditures, the results showed that participants consuming the least amount of added sugars had higher HDL (good) cholesterol, lower triglycerides and lower LDL (bad) cholesterol.  The researchers concluded that there was an important association between increased sugar consumption and cardiovascular risk factors.  In another recent study, consumption of sugar-sweetened beverages was associated with significantly elevated blood pressure and increased BMI[5]

What does it all mean? 

Obesity, altered blood lipids, hypertension and insulin resistance adds up to metabolic syndrome; one of, if not the major risk factor for heart disease and diabetes.  While it hasn’t been conclusively determined what initially causes metabolic syndrome or what the initial event is in the insulin resistance cascade, there seems to be a remarkably strong correlation between liver fat and insulin resistance.[6]   Insulin resistance, obesity and metabolic syndrome are also closely associated with an increased risk of cancer.[7] 

If sugar consumption leads to insulin resistance, and insulin resistance is one of the fundamental underlying defects in cancer, as it is in type-2 diabetes and heart disease, then it seems to follow that excessive sugar consumption may cause cancer.  Even if the final scientific conclusions are not in, isn’t the association enough to make you rethink how much sugar you are willing to consume?

[1] Glinsmann W, et al.  Evaluation of Health Aspects of Sugars Contained in Carbohydrate Sweeteners. FDA Sugar task Force. 1986

[2] Johnson, R.K. et al. Dietary sugars intake and cardiovascular health. A scientific statement from the American Heart Association. Circulation 120, 1011-1020 (2009

[3] Forshee et al. Crit Rev Food Sci Nutr. 2007;47(6):561-82

[4] Ouyang X, Cirillo P, Sautin Y, McCall S, Bruchette JL, Diehl AM, Johnson RJ, Abdelmalek MF. Fructose consumption as a risk factor for non-alcoholic fatty liver disease. J Hepatol. 2008 Jun;48(6):993-9. Epub 2008 Mar 10.                    

[5] 1.Ian J. Brown, Jeremiah Stamler, Linda Van Horn, Claire E. Robertson, Queenie Chan, Alan R. Dyer, Chiang-Ching Huang, Beatriz L. Rodriguez, Liancheng Zhao, Martha L. Daviglus, Hirotsugu Ueshima, Paul Elliott, and for the International Study of Macro/Micronutrients and Blood Pressure Research Group. Sugar-Sweetened Beverage, Sugar Intake of Individuals, and Their Blood Pressure: International Study of Macro/Micronutrients and Blood Pressure. Hypertension, February 28, 2011

[6] Adiels M, Taskinen MR, Borén J. Fatty liver, insulin resistance, and dyslipidemia. Curr Diab Rep. 2008 Feb;8(1):60-4. 

[7] Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective. World Cancer Research Fund, 2007.