Sugars are fattening. Of that, there is really little doubt. Almost everybody can agree upon this fact. The reason it is fattening is a little more contentious. Some consider sugar as empty calories since they contain few essential nutrients. Others think that sugar makes food more ‘palatable’ and thus cause us to overeat these foods. In a similar vein, sugar may be more ‘rewarding’ and thus cause overeating and obesity. Sugar is also a carbohydrate, which may be the mechanism of its fattening effect. Others, such as Dr. Robert Lustig considers sugar to be a poison. His internet lecture became a viral sensation. All I can say is that, while I generally agree with his position, a poison that requires daily consumption for 70 years or more to kill is not a very strong poison. I do use the analogy of poison referring to carbohydrates and fibre but always in quotations because it is not to be taken literally. Carbohydrates, even sugars are not literally poisonous.
All of these effects are plausible and we need to look further into the dangers of fructose specifically. Where does fructose fit in? Fructose does not raise the blood sugars appreciably, yet is more strongly linked to obesity and diabetes than glucose. Fructose also is not more rewarding than glucose. Fructose is just an empty a calorie as glucose. So why is fructose so bad?
First, we need a few definitions so that we are clear about what we are talking. The 6 ring sugar that is found in the blood is called glucose. It can be used by virtually all cells in the body. In the brain, for example, it is considered the preferred energy source. Muscle cells will greedily import glucose from the blood for a quick energy boost. Glucose is stored in the body in various forms such as glycogen in the liver. Under stress situations (flight or fight response) the body will release glucose for quick energy boost. Glucose circulates throughout the body with virtually no limitation. There are glucose receptors in many different tissues and organ systems.
Fructose, on the other hand, is a 5 ringed sugar. It is the sugar that is found naturally in fruit. It is metabolized in the liver and does not circulate as fructose. The body has no ability to use fructose in its natural form. The brain cannot use fructose. The muscles cannot use fructose. For this reason, fructose ingestion does not appreciably change the blood sugars (blood glucose).
Table sugar is called sucrose. This is composed of two sugars linked together. There is one molecule of glucose which is linked to one molecule of fructose. This is the form that we are most familiar with.
Carbohydrates can be classified in different ways. An older, less useful manner of classification was the distinction between simple and complex carbohydrates. While this terminology is still sometimes used, it was long ago recognized that it provided little useful information.
Simple carbohydrates consisted of 1-2 sugars linked together. These were also called mono and disaccharides. These were predominantly glucose, fructose and sucrose, although other sugars included lactose.
Complex carbohydrates are long chains of sugars. That’s it. There is no need to have fibre, micronutrients, vitamins or other. Highly refined white flour is a complex carbohydrate. The reason for this classification was the mistake idea that complex carbohydrates are slower to be digested due to the chain length. With further investigation into the Glycemic Index, this is not really true at all. White bread, for instance has a very high glycemic index comparable to sugar.
This simple vs complex classification is not useful because it only distinguished the chain length, which we are not really interested in. If we are interested in the glycemic effect, then we should measure it directly and use the Glycemic Index. However, as noted previously, this, too has its problems.
The main problem with the sugars sucrose and fructose, in general is dosage. Consumption of sugar has been increasing recently and this has been closely paralleled by the rising obesity rates and diabetes.
The release of the 1977 Dietary Guidelines for Americans warned about the dangers of too much sugar. However, this message got lost in the anti-fat crusade that followed. Consumption of sugar increased sharply beginning in 1977 as we became more and more concerned about the fat contents of our foods. Since fat was the predominant, overwhelming concern of health conscious shoppers, the sugar content was ignored or forgotten.
Bags of jellybeans and other such candies were proudly proclaiming themselves to be low in fat despite the fact that they were virtually 100% sugar. In essence, we had ‘taken our eyes off the ball’. The goal was better health and even in 1977 guidelines recognized that sugar was certainly just as bad as fats. It turns out, of course, that dietary fats are not nearly as bad as they were made out to be, but that is a story that will need to wait.
The worst offender in the sugar story by far, is the sugar-sweetened beverage (SSB) – soft drinks, sodas and more recently, sweetened teas and juices. In both children and adults, the consumption of SSB and juices rose throughout the decades to peak at roughly year 2000. Milk, the traditional beverage of children began to fall and fall. By the year 2000, SSB provided 22% of the sugar found in the American diet compared to 16% in 1970. No other food group even comes close.
Despite the gloom and doom of all the recent hype about the obesity crisis, there shines a ray of hope in the accompanying graph. By year 2000, we had realized that we had lost our way. Under the Atkins Onslaught, we were forced to face the fact that sugar was indeed a dietary villain. Sugar had never been considered a health food, but had gotten a free ride as we concerned ourselves obsessively with dietary fat.
Sugar sweetened beverages started to decline in popularity. Iced sweetened teas and sports drinks have valiantly tried to take their place but have been unable to stem the tide. Soda is a $75 billion industry that has until recently seen nothing but good times. In the 1970’s people doubled their intake of the fizzy stuff. By the 1980s, it was more popular than tap water. By 1998, Americans were drinking 56 gallons per year. But in 2014, Coca Cola has faced 9 consecutive years of sales decline as health concerns mount. The demographic of the baby boomer likely plays a role as well, since older folks are less likely to drink the toxic stuff. Now, SSB face strong opposition, from soda taxes to the recent effort by Michael Bloomberg to outlaw outsized beverages. Some of the problems, of course, are of their own making. Coca Cola, for instance spent decades trying to convince us to drink more soda. They were successful, but at what cost? As the obesity crisis grew, the companies found themselves under increasing fire.
It is fascinating to compare the original McDonalds fountain drink of (7 oz) to the current kid’s size (12 oz). Pure marketing genius. Too smart for themselves by far.
For many health reasons, losing weight is important. It can improve your blood sugars, blood pressure and metabolic health, lowering your risk of heart disease, stroke and cancer. But it’s not easy. That’s where we can help.