What Are The Differences Between Glucose And Fructose?

Simple sugars can have a negative impact on body composition and metabolic health in sedentary people.

Do you know the differences between glucose and fructose? Do you know which one is best for you? The two are isomers, that is, they have the same chemical formula, but their molecular structure is different. Therefore, their metabolic pathways differ, along with their effects on the body.

the glucose

Glucose, like fructose, is a monosaccharide. Its glycemic index is high and therefore it is a substance that increases blood glucose as quickly as it is absorbed. This condition makes it a harmful substance to health, as stated in an article published in the journal Cell Metabolism.

It is found in many foods in the form of glucose or starch (union of glucose molecules). However, as a household sweetener, it is difficult to find it in a format other than table sugar.

the fructose

Fructose is the sugar with the greatest sweetening power. Paradoxically, its ability to increase blood glucose is much less than that of glucose. Your glycemic index is rated low.

Unlike glucose, it is easy to find freely for home use. Furthermore, it is the favorite sweetener in the food industry for its low cost and high sweetening capacity.

In natural foods, we find fructose mainly in fruits. However, the harm that we will detail below is not attributable to its consumption. This is due to the fact that fructose density is very low and its fiber richness reduces and delays its absorption.

Cardiometabolic differences between glucose and fructose

The metabolic pathways of fructose and glucose differ due to their structural differences.

The structural differences between glucose and fructose cause their metabolic pathways to differ and therefore their impact on the body is also different.

The body’s energy fuel

Glucose reaches every cell in our body through specific transporters (highlighting GLUT2, GLUT3 and GLUT4). This means that all our cells use glucose as their main energy fuel.

However, the fructose GLUT5 utilizes carriers and can only form hepatic glycogen and fatty acids. That is, it is only absorbed by hepatocytes and adipocytes. This translates into less opportunity for use and a greater tendency to accumulate body fat.

Appetite

A study published in 2019 shows that glucose consumption increases appetite. This is likely due to its ability to stimulate the production of insulin spikes and the consequent withdrawal of glucose from the blood. Therefore, it is the decrease in blood glucose that is responsible for the increase in appetite.

Fructose, glucose and adiponectin

Adiponectin is a protein secreted mainly by adipocytes and cardiomyocytes. Its level is inversely proportional to the percentage of body fat and is reduced in obesity and diabetes mellitus states.

In addition, it has an important role in the regulation of energy metabolism, as:

Favors the oxidation of fatty acids.
Reduces plasma triglycerides.
Increases insulin sensitivity.

In this sense, it is known that glucose has a greater capacity than fructose to induce the release of adiponectin and achieve the benefits associated with its increase.

Glucose induces greater release of adiponectin.

metabolic control

The metabolic pathway of fructose is less controlled than that of glucose. For example, fructose does not depend on sodium to enter cells. Thus, all fructose consumed travels from the intestine to the liver to be metabolized.

Furthermore, fructose cannot be accumulated as muscle glycogen or used by cells other than adipocytes and hepatocytes. This, together with the ease of entry into the cell, means a rapid activation of lipogenesis (body fat formation).

Fatty acids

Fructose reduces fatty acid oxidation and increases lipid synthesis in the liver. Thus, its excessive consumption has been linked to liver overload and fatty liver.

Considering that most processed foods contain fructose, and that the consumption of these foods has increased, it does not seem very difficult to over-intake. The excess seems even easier if we think that many people choose to consume it as a sweetener due to its low glycemic index.

The effect of glucose and fructose consumption on aortic artery relaxation

Akther, Alegret, Laguna, Roglans, Roshanak, Sangüesa and Shaligram (2017) studied the effects of glucose and fructose consumption in a population of rats exposed to a nitric oxide donor agent and found that the aorta artery was less able to relax in rats that received fructose.

This assumes a worse cardiovascular status and a lower response to the most used pharmacological treatment (nitroglycerin) for ischemic heart diseases (obstruction of blood flow in the cardiac muscle).

Fructose implies a worse metabolic and cardiovascular state

Based on the above, although glucose consumption increases appetite, studies show that fructose is probably the carbohydrate with the greatest obesogenic capacity. In fact, its consumption has been linked to the famous “metabolic syndrome“.

Furthermore, fructose consumption has been linked to insulin resistance, a worse lipid profile and an inadequate cardiovascular response.

Metabolic syndrome includes: excess abdominal fat, high blood pressure, diabetes mellitus, hypertriglyceridemia and decreased HDL protein (good cholesterol).

Practical considerations based on the differences between glucose and fructose

We already know what the differences between glucose and fructose are and their impact on health, but what does this information mean in everyday life?

What do I do with fructose?

As we have seen, despite its low glycemic index, its consumption entails an infinite number of negative effects that culminate in more obesity, diabetes, liver disease and everything that these diseases bring with them.

In this regard, we must keep in mind that most processed foods contain fructose among their ingredients. Today, you have one more reason to abandon the consumption of processed foods.

When to consume glucose?

One of the big differences between glucose and fructose is their ability to increase blood glucose. Therefore, we must choose glucose consumption in cases where we need a quick energy intake. This can happen during intense physical exercise or at the end of it.

If the energy demand is very high (intense physical activity longer than 2.5-3 hours), it would be convenient to choose carbohydrates combined with a high glycemic index. This translates to honey, table sugar or the concomitant use of free glucose and fructose.

In this way, we would be saturating all the transporters that carry sugar to the cells and, therefore, satisfying the energy demand.

A Low Glycemic Index Alternative

However, in all other circumstances, we should not opt for glucose. At the same time, we should not opt for fructose either, as, despite its low glycemic index, it has a very negative cardiometabolic impact. Caloric sweeteners are not a good alternative either.

Glucose and fructose are generally not recommended.

For all those moments that are not before or after intense physical exercise, the ideal would be a glucose with a low glycemic index, but unfortunately it does not exist. So our best alternative is coconut sugar.

Coconut sugar is a natural sweetener based on sucrose (50% glucose and 50% fructose) and its glycemic index is low. As it is not refined, its water and fiber content is superior to other sweeteners. This reduces the proportion of sucrose in each serving.

Don’t forget that as long as you don’t need an immediate contribution of energy, your intake of free sugars (whatever they are) should be as low as possible.