Modern man is plagued with many diseases that you will not find in some "primitive" populations like modern hunter-gatherers.
These include obesity, heart disease, some cancers and last but not least, type II diabetes... which has reached epidemic proportions in the past few decades and now afflicts about 300 million people worldwide.
This disease is a common cause of early death, blindness, amputation and a severely decreased quality of life... and it is advancing rapidly, every single year.
In the above, Dr. Robert H. Lustig and Dr. Elissa S. Epel explain how excess sugar can mess up liver metabolism and ultimately lead to diabetes.
Dr. Lustig recently took part in a study where they examined the associations between sugar consumption and diabetes in 175 countries ().
They found very , where each 150 kcal (about one can of soda) per day of sugar increased the prevalence of diabetes by 1.1%.
To put this number in perspective, if all of the U.S. added to their daily diet, almost 3.5 million more people would become diabetic.
In this study, added sugar was the only part of the diet that correlated with diabetes when they adjusted for confounding factors.
These types of studies are so-called observational studies, which can not prove that one thing caused another, it can only show that they are correlated.
However, there are other lines of evidence linking sugar to the development of type II diabetes and this specifically involves how sugar affects the liver.
Sugar is composed of two molecules... glucose and fructose. Glucose can be metabolized by every cell in the body and if we don't get it from the diet, our bodies make it.
However, fructose is different. The only organ that can metabolize sugar is the liver, because only the liver has a transporter for it ().
Athletes or highly active individuals can eat quite a bit of fructose without problems, because their livers will turn the fructose into glycogen - a storage form of glucose in the liver.
However, when someone's liver is already full of glycogen (which is true of most people), the fructose will be turned into fat ().
Some of the fat gets shipped out as blood triglycerides while part of it remains in the liver, contributing to non-alcoholic fatty liver disease (, ).
At the same time, your liver becomes insulin resistant. This causes elevated insulin all over your body, which can lead to obesity, metabolic syndrome and many other diseases (, ).
Eventually, the pancreas will become unable to secrete sufficient insulin to drive blood glucose into cells.
At this point, blood sugar levels elevate significantly... and that's when a diagnosis of is made.
Fructose is harmful in the context of excess calories. If we eat small amounts or we are already in a calorie deficit, fructose will not cause harm.
Fruits are a real food with a low energy density, lots of water and significant chewing resistance. It is almost impossible to overeat fructose by eating whole fruit.
There are a few instances where minimizing fruit might be a good idea.
If you are:
b) Very carb sensitive.
c) Eating a very low-carb ketogenic diet.
...then you should probably avoid fruit as much as possible, except perhaps for the occasional berries.
But for healthy people trying to stay healthy, there is no proven reason to avoid natural, whole fruit.
What Dr. Lustig says applies to excess fructose from added sugars. It does NOT apply to moderate consumption of fruit.