This is a very new concept!
In the past we have felt that your diet was semi-important to health because you might eat too many calories and get fat, or not get enough vitamins, but it wasn't a big deal. We had also found that some foods contain dangerous bacteria or toxins, such as salmonella or botulism. These are very rare cases, and often result in the destruction of huge quantities of perfectly good food, but usually only a few individuals were affected.
Many Common Foods Contain Simple but Dangerous Toxins
Just in the past few years, nutritional scientists have discovered that two commonly eaten substances can be extremely toxic and can ruin your health and eventually kill you. Specifically, these are fructose and transfats.
The old way of looking at food was to count total calories, try to get enough fiber and vitamins, and eat enough junk food to fill up the rest of your caloric needs. Junk food is pretty easy for most people to identify, and it usually is characterized by a high sugar content. Now we know that junk food (high in transfat or sugar) is actually toxic to the body.
Why do people consume so much sugar and fat? Partly because fructose is addicting (see Health-Byte on fructose) and partly because fructose is added to thousands of processed foods and we don't even realize it's there. (Who would guess that catsup is made from high fructose corn syrup?) Another factor is that the fructose industry is very sophisticated at selling its product. Advertising for "sports drinks" is so intense that we have all grown up convinced that Gatorade actually promotes health rather than destroying your health (see the movie "Idiocracy"!).
The food industry may be a major obstacle for health care reform!
Should we totally avoid eating any sugar or fat? Let's look at fat first. Fat is food that is calorie-dense (9 calories per gram, compared to 4 calories per gram for carbs) but it is not toxic. It is digested and enters the metabolic pathways in your body in a controlled way. Some types of fat (saturated fats and transfat) have been associated with higher rates of heart disease in large population studies, but this may be a secondary effect from the fructose that often accompanies a high fat diet.
Now let's look at fructose. Regular table sugar, honey, brown sugar, and high fructose corn syrup are the major sources of the toxin fructose. Fructose is not regulated by our body's metabolic hormones, and generally degrades into free fatty acids and triglycerides in the liver, which then fill up the bloodstream with these dangerous forms of lipids. The body can tolerate small amounts of fructose, such as the amount in fresh fruit, but the total fructose intake can skyrocket when everything you eat has fructose added. Plus you get an occasional giant blast of fructose from drinking a soda, sports drink or fruit juice. Even a small glass of orange juice has 6 times the amount of fructose as a whole orange, but none of the beneficial fiber.
If your diet includes fructose on a regular basis, you are putting yourself at high risk for diabetes, cardiovascular disease such as stroke and heart attack, as well as liver disease and many other diseases, as well as obesity.
Many foods are beneficial to your health, such as foods high in vitamins, fiber and anti-oxidants. Just eating a diet with lots of variety of fruits and vegetables will provide all these benefits. You should also try to eat some foods that have healthy oils, such as olive oil and fish. Other than that, you don't have to load up on blueberries or drink excess omega this or that.
The American Heart Association has published the very first sugar restriction guidelines (Sept 2009) which recommend a severe restriction for both men and women. Men should eat no more than 150 calories and women no more than 100 calories of added sugar. That's not much sugar! You would get more than that just in the traces of sugar that are added to EVERY food you buy at the store.
Bottom line: Fructose (found in all types of sugar and high fructose corn syrup) is toxic to your body and can ruin your health. Irregardless of your weight, you should avoid eating or drinking fructose whenever possible. The easiest way to cut down on sugar is to eliminate sugar from 100% of all beverages that you drink. This includes drinks that may seem healthy such as fruit juice or sports drinks. (These drinks are actually dangerous to your health because of the high fructose content.)
To learn more about how fructose affects your body, see the Health-byte on Fructose.