The central health claim of GCBC is that carbohydrates cause a lot of the lifestyle related illnesses that are rampant in western civilizations. The metabolic link between carbohydrates and heart disease, diabetes, or cancer is complicated. Overall, it’s summed up in the book as metabolic syndrome, a disorder in how the body produces and uses insulin.

Modern medical literature seems to treat metabolic syndrome as just a description of several symptoms that tend to appear together. The main symptom is having fat in organs not best suited for storing fat; other symptoms include high blood pressure, insulin resistance, and low levels of HDL. Once someone has metabolic syndrome, their likelihood of developing heart disease or diabetes skyrockets.

According to GCBC, the symptoms of metabolic syndrome all stem from the blood-sugar spikes that come from eating processed carbohydrates. This is also the accepted cause of diabetes, and GCBC makes the claim that diabetes is just a more advanced form of metabolic syndrome. If this is so, then the fact that diabetics are so much more likely to develop heart disease than non-diabetics can help explain the link between carbohydrates and heart-disease.

In order to understand how metabolic syndrome develops from eating carbohydrates, we have to understand how two different forms of sugar are metabolized in the body. Most sugars are made up of about half glucose and half fructose.

Glucose

Glucose is the fuel for cells in the body. When glucose is consumed, it eventually makes its way to the blood stream. As far as I can tell, glucose is the only sugar that counts as blood sugar. Once in the blood stream, insulin in the blood allows the glucose to be taken into a cell. The glucose can then be metabolized by mitochondria to provide the cell with the energy it needs to stay alive and do its thing.

This is why the pancreas produces insulin after you eat. Blood sugar is going up, so the body needs insulin in order to use the glucose.

Fructose

Fructose is digested much differently than glucose. It can’t be processed anywhere except the liver.

Since it can’t be used in most of the body, fructose doesn’t cause an insulin spike or count as blood sugar. Instead, it get’s converted into triglycerides in the liver, which VLDL then transports to fat cells for storage. Remember from the post on fat that VLDL is highly associated with heart disease. Turns out VLDLs probably cause heart disease because they lead to physically smaller LDLs. Those smaller LDLs can make their way into damaged areas of an artery wall and cause plaques.

Furthermore, when the liver has high levels of fructose in it, it focuses on the fructose and ignores all the glucose. This means that the blood glucose levels stay higher longer, in turn prompting the pancreas to produce even more insulin.

Insulin

So glucose directly causes insulin to rise. Fructose causes it to rise indirectly, by decreasing glucose metabolism in the liver. Why does that matter?

What I didn’t know before reading this book is that insulin is not just used to allow uptake of glucose. It’s also used to regulate fat storage within the body. Higher levels of insulin cause fat to be stored, rather than burned for energy. If insulin is high for long enough, organs in the body will start to put on fat. That’s exactly the primary symptom of metabolic syndrome mentioned above.

Chronic high insulin levels cause body tissues to become less sensitive to insulin. That’s when diabetes type 2 develops. Your body is still make insulin in response to the blood sugar floating around, but your tissue ignores it more. In order to overpower the insulin resistance, type 2 diabetics often have to take insulin injections.

Metabolic Syndrome in Action

To sum up the first half of the book, metabolic syndrome is the true cause of many of the diseases of western civilization. The symptoms of metabolic syndrome, according to GCBC, are all caused by eating too much sugar and simple carbohydrates. High levels of fructose will lead to heart disease through the formation of small LDLs. High levels of glucose will lead to insulin resistance, which in turn leads to diabetes and fat in places it shouldn’t be.

That’s about all there is to it, and that’s about exactly the opposite advice that I got about the effect of diet on health up until reading this book.