Carbohydrate Tolerance

We are all different and our tolerance to carbohydrates also differs depending on:

• the quantity of carbohydrates consumed
• the quality of these carbohydrates
• the amount of time we've been consuming these different types of carbohydrates
• the genetic profile of the individual.

If someone is gaining weight or cannot lose it with exercise. Or if someone has metabolic syndrome or diabetes, it means that the person has an intolerance to the load of carbohydrates consumed.

These patients could be called "allergic" to carbohydrates. We would not want them to include these in their diet, as we would not advise a milk intolerant to consume dairy products.

Some people do very well just by eliminating sugary foods (soft drinks, pastries etc.) from their diet, others might need to reduce their starch intake as well.

These are the steps to diabetes:

• When carbohydrates are in short supply, they are taken up and stored by the liver (for later use) in the form of glycogen. 
• If the person's liver is replete, the carbohydrates consumed will circulate in the bloodstream, prompting the pancreas to release insulin, in order to bring down glucose levels.
• Extra glucose will be stored as fat in the adipose tissue with the help of insulin.
• Decades of high glucose levels and subsequent hyperinsulinemia (high insulin levels) lead to diabetes.

According to Robert Lustig, all carbohydrates are not created equal. Here is an excerpt from his book Fat Chance:

Glucose [...]

1. Glucose metabolism is insulin-dependent. Consuming glucose raises the glucose level in the bloodstream, stimulating insulin release, which promotes energy storage into fat cells and causes weight gain.
2. The overwhelming majority of glucose in the liver will be directed toward forming glycogen, or liver starch, which is not harmful to the liver cell. This also will keep the liver from releasing glucose into the blood, preventing diabetes.
3. A small amount of glucose will be metabolized by the liver mitochondria for energy.
4. Any excess glucose in the liver that is not shunted to glycogen and not metabolized by the mitochondria for energy will instead be converted to triglycerides. High triglyceride levels in the blood can promote the development of cardiovascular disease.
5. Glucose can bind to proteins in the cell, which causes two problems:

• When glucose binds to proteins throughout the body, the proteins become less flexible, contributing to the ageing process and causing organ dysfunction.
• Every time a glucose molecule binds to a protein, it releases a reactive oxygen species (ROS), which can cause tissue damage if not immediately mopped up by an antioxidant in the peroxisome. [...]

Ethanol (Grain Alcohol)

Ethanol is a naturally occurring by-product of carbohydrate metabolism, called fermentation. [...]

1. After ethanol enters the liver in high dosages, it can promote ROS formation and cell damage.
2. In contrast to glucose, which went to glycogen, the ethanol goes straight to the mitochondria.
3. Any excess gets turned into fat by a process called de novo (new) lipogenesis (fat-making). The lipid [fat] buildup can lead to liver insulin resistance and inflammation.
4. If this process continues, it can eventually cause alcoholic fatty liver disease. This is a surefire prescription for slow death or, at best, a liver transplant.
5. Alternatively, the lipid can exit the liver and take up residence in skeletal muscle, where it also induces insulin resistance and can cause heart disease.
6. Lastly, ethanol enhances its own consumption, by acting on the brain's reward pathway. When this goes out of control, addiction sets in. [...]

Fructose

Fructose is never found alone in nature. Rather it is always partnered with its more benign sister molecule, glucose. They both have the same chemical composition (C₆H₁₂O₆) but they are hardly the same. Fructose is much worse. Let's start with the Maillard, or "browning", reaction. This is the same reaction that turns hemoglobin in your red blood into hemoglobin A1c (HbA1c), the lab test that doctors follow to determine how high a diabetic patient's blood sugar has risen over time. The reaction product is brown; this is the reason bananas turn brown with time [...]. Fructose drives the Maillard reaction seven times faster than glucose. This seemingly subtle difference can cause every cell in the body to age more rapidly, driving various degenerative processes such as ageing, cancer, and cognitive decline.
There are dozens of studies that now implicate fructose as a major player in causing metabolic syndrome. In fact, it's metabolized a lot like ethanol [...]

1. Triple the dose means the liver needs triple the energy to metabolize this combo versus glucose alone, depleting the liver cell of adenosine triphosphate (or ATP, the vital chemical that conveys energy within cells). ATP depletion leads to the generation of waste product uric acid. Uric acid causes gout and increases blood pressure.
2. The fructose does not go to glycogen. It goes straight to the mitochondria. Excess acetyl-Coa is formed, exceeding the mitochondria's ability to metabolize it.
3. The excess acetyl-Coa leaves the mitochondria and gets metabolized into fat, which can promote heart disease.
4. Fructose activates a liver enzyme, which is the bridge between liver metabolism and inflammation. This inactivates a key messenger of insulin action, leading to liver insulin resistance.
5. The lack of insulin effect in the liver means that there is no method to keep the glucose down, so the blood glucose rises, which can eventually lead to diabetes.
6. the liver insulin resistance means the pancreas has to release extra insulin, which can force extra energy into fat cells, leading to obesity. And the fat cells that fill up most are visceral fat, the bad kind associated with metabolic disease.
7. The high insulin can also drive the growth of many cancers.
8. The high insulin blocks leptin signaling, giving the hypothalamus the false sense of "starvation" and causing to eat more.
9. Fructose may also contribute to breakdown of intestinal barrier. Normally the intestine prevents bacteria from entering the bloodstream. The intestinal breakdown may lead to a breach in the walls of the intestine. The result is "leaky gut", which could increase the body's exposure to inflammation and more ROS. This worsens insulin resistance and drives insulin levels even higher.
10. Fructose undergoes the Maillard (browning) reaction 7 times faster than glucose, which can damage cells directly. Altough the experiments are in their infancy, preliminary results suggest that in a susceptible environment, fructose can accelerate ageing and the development of cancer.
11. The data on fructose and dementia in humans are currently correlative and indirect. However, data on insulin resistance and dementia show clear causation. [...]