Whenever I refer to fructose as toxic, there’s plenty of discussion in response about how much fructose is metabolized as energy, converted into glucose, or converted into triglycerides deposited in the liver and body fat.

My statements stating over 90% of fructose is converted into liver fat through denovo lipogenesis by the liver need some clarification. 

The details and variables in fructose metabolism are relatively new discoveries, and the fate of dietary fructose changes significantly depending on the metabolic scenario. 

Fructose can have a 40 to 79%metabolism rate, meaning not all of it will be metabolized and will vary depending on how it is consumed, if it is combined with glucose or other nutrients, and the metabolic profile of the one consuming it.

Here are some of the details that make it hard to give a short and direct answer:

1. Fructose does not get stored as glycogen in the liver or muscles. Still, it can be converted to glucose, which depends on the individual’s metabolic state, health, glycogen capacity, and needs.
2. Fructose can be used directly as fuel using the glucose enzymes and cofactors but rarely does unless exercising with a high intensity right after ingestion, and that will vary depending on the individual’s fitness level. 
3. Fructose does get converted into triglycerides and stored both as liver fat and sent through the bloodstream to be stored as body fat, depending on the history of consuming fructose, types of fructose consumed, and how the pathway has adapted. 
4. Fructose doesn’t raise blood sugar or insulin, indicating that most of the metabolism is done in the liver, stored as liver fat, and sent out as triglycerides.
5. This independent pathway from insulin resistance for storing liver and body fat will contribute to insulin resistance and possibly cause it outright when over-activated long enough.

If it seems confusing, I agree. 

So, when I refer to the fate of fructose as over 90% being stored as fat in the liver, I am speaking of the most likely fate in the body of the general public. 

The only way to assume that fructose is taking a different combination of pathways that would change this fate is by not having fructose in your diet prior. 

The natural threshold for dietary fructose is about 5-6 grams. 

This amount can be metabolized in the gut and not reach the liver. If we consume more than that at any one meal or snack, the liver will likely turn it into liver fat, raise triglycerides, and signal the brain to reduce our cellular metabolism. 

When people google fructose metabolism, Wikipedia says, “Under one percent of ingested fructose is directly converted to plasma triglyceride. 29% – 54% of fructose is converted in the liver to glucose, and about a quarter of fructose is converted to lactate. 15% – 18% is converted to glycogen. Glucose and lactate are used normally to fuel cells all over the body.”

This is a very misleading and oversimplified statement when you consider the significant diversity in metabolic responses that can occur. It is just one possibility and assumes a healthy metabolism and a healthy person is consuming it. 

Still, the odds of that happening just as described are found primarily in theory. 

When you look at the net effect and probability of how fructose is metabolized in most people, it tells a different story. Although considered natural, its response is toxic in most cases.

Fructose is toxic because it is being dramatically over-consumed and has been for most people’s lives. 

As it was, it has altered and damaged the natural metabolism and response to it in the body. 

That has to be repaired, the pathways and responses returned to healthy standards, and the insulting toxin, fructose, eliminated or significantly reduced and often avoided.

Changing one’s diet, just like when trying to reverse insulin resistance or chronic lifestyle diseases, will slow the negative progression but will not fix the problem. 

One must change more aspects of their lifestyle to fix the problem, including diet, using metabolic exercise, and incorporating functional rotational fasting.

It can be done, and we can do better!

Dr. Don